SVI Добавление вендоринга

go.mod

@@ -2,10 +2,14 @@ module git.p78su.freemyip.com/svi/gostore
 
 go 1.21.1
 
-require github.com/gofiber/fiber/v2 v2.50.0
+require (
+	github.com/gofiber/fiber/v2 v2.50.0
+	github.com/syndtr/goleveldb v1.0.0
+)
 
 require (
 	github.com/andybalholm/brotli v1.0.6 // indirect
+	github.com/golang/snappy v0.0.4 // indirect
 	github.com/google/uuid v1.4.0 // indirect
 	github.com/klauspost/compress v1.17.2 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect

go.sum

@@ -1,9 +1,16 @@
 github.com/andybalholm/brotli v1.0.6 h1:Yf9fFpf49Zrxb9NlQaluyE92/+X7UVHlhMNJN2sxfOI=
 github.com/andybalholm/brotli v1.0.6/go.mod h1:fO7iG3H7G2nSZ7m0zPUDn85XEX2GTukHGRSepvi9Eig=
+github.com/fsnotify/fsnotify v1.4.7/go.mod h1:jwhsz4b93w/PPRr/qN1Yymfu8t87LnFCMoQvtojpjFo=
 github.com/gofiber/fiber/v2 v2.50.0 h1:ia0JaB+uw3GpNSCR5nvC5dsaxXjRU5OEu36aytx+zGw=
 github.com/gofiber/fiber/v2 v2.50.0/go.mod h1:21eytvay9Is7S6z+OgPi7c7n4++tnClWmhpimVHMimw=
+github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/golang/snappy v0.0.0-20180518054509-2e65f85255db/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
+github.com/golang/snappy v0.0.4 h1:yAGX7huGHXlcLOEtBnF4w7FQwA26wojNCwOYAEhLjQM=
+github.com/golang/snappy v0.0.4/go.mod h1:/XxbfmMg8lxefKM7IXC3fBNl/7bRcc72aCRzEWrmP2Q=
 github.com/google/uuid v1.4.0 h1:MtMxsa51/r9yyhkyLsVeVt0B+BGQZzpQiTQ4eHZ8bc4=
 github.com/google/uuid v1.4.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
+github.com/hpcloud/tail v1.0.0 h1:nfCOvKYfkgYP8hkirhJocXT2+zOD8yUNjXaWfTlyFKI=
+github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
 github.com/klauspost/compress v1.17.2 h1:RlWWUY/Dr4fL8qk9YG7DTZ7PDgME2V4csBXA8L/ixi4=
 github.com/klauspost/compress v1.17.2/go.mod h1:ntbaceVETuRiXiv4DpjP66DpAtAGkEQskQzEyD//IeE=
 github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=
@@ -13,16 +20,38 @@ github.com/mattn/go-isatty v0.0.20 h1:xfD0iDuEKnDkl03q4limB+vH+GxLEtL/jb4xVJSWWE
 github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
 github.com/mattn/go-runewidth v0.0.15 h1:UNAjwbU9l54TA3KzvqLGxwWjHmMgBUVhBiTjelZgg3U=
 github.com/mattn/go-runewidth v0.0.15/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
+github.com/onsi/ginkgo v1.6.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
+github.com/onsi/ginkgo v1.7.0 h1:WSHQ+IS43OoUrWtD1/bbclrwK8TTH5hzp+umCiuxHgs=
+github.com/onsi/ginkgo v1.7.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
+github.com/onsi/gomega v1.4.3 h1:RE1xgDvH7imwFD45h+u2SgIfERHlS2yNG4DObb5BSKU=
+github.com/onsi/gomega v1.4.3/go.mod h1:ex+gbHU/CVuBBDIJjb2X0qEXbFg53c61hWP/1CpauHY=
 github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
 github.com/rivo/uniseg v0.4.4 h1:8TfxU8dW6PdqD27gjM8MVNuicgxIjxpm4K7x4jp8sis=
 github.com/rivo/uniseg v0.4.4/go.mod h1:FN3SvrM+Zdj16jyLfmOkMNblXMcoc8DfTHruCPUcx88=
+github.com/syndtr/goleveldb v1.0.0 h1:fBdIW9lB4Iz0n9khmH8w27SJ3QEJ7+IgjPEwGSZiFdE=
+github.com/syndtr/goleveldb v1.0.0/go.mod h1:ZVVdQEZoIme9iO1Ch2Jdy24qqXrMMOU6lpPAyBWyWuQ=
 github.com/valyala/bytebufferpool v1.0.0 h1:GqA5TC/0021Y/b9FG4Oi9Mr3q7XYx6KllzawFIhcdPw=
 github.com/valyala/bytebufferpool v1.0.0/go.mod h1:6bBcMArwyJ5K/AmCkWv1jt77kVWyCJ6HpOuEn7z0Csc=
 github.com/valyala/fasthttp v1.50.0 h1:H7fweIlBm0rXLs2q0XbalvJ6r0CUPFWK3/bB4N13e9M=
 github.com/valyala/fasthttp v1.50.0/go.mod h1:k2zXd82h/7UZc3VOdJ2WaUqt1uZ/XpXAfE9i+HBC3lA=
 github.com/valyala/tcplisten v1.0.0 h1:rBHj/Xf+E1tRGZyWIWwJDiRY0zc1Js+CV5DqwacVSA8=
 github.com/valyala/tcplisten v1.0.0/go.mod h1:T0xQ8SeCZGxckz9qRXTfG43PvQ/mcWh7FwZEA7Ioqkc=
+golang.org/x/net v0.0.0-20180906233101-161cd47e91fd/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
+golang.org/x/net v0.8.0 h1:Zrh2ngAOFYneWTAIAPethzeaQLuHwhuBkuV6ZiRnUaQ=
+golang.org/x/net v0.8.0/go.mod h1:QVkue5JL9kW//ek3r6jTKnTFis1tRmNAW2P1shuFdJc=
+golang.org/x/sync v0.0.0-20180314180146-1d60e4601c6f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sys v0.0.0-20180909124046-d0be0721c37e/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20220811171246-fbc7d0a398ab/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.13.0 h1:Af8nKPmuFypiUBjVoU9V20FiaFXOcuZI21p0ycVYYGE=
 golang.org/x/sys v0.13.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/text v0.8.0 h1:57P1ETyNKtuIjB4SRd15iJxuhj8Gc416Y78H3qgMh68=
+golang.org/x/text v0.8.0/go.mod h1:e1OnstbJyHTd6l/uOt8jFFHp6TRDWZR/bV3emEE/zU8=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/fsnotify.v1 v1.4.7 h1:xOHLXZwVvI9hhs+cLKq5+I5onOuwQLhQwiu63xxlHs4=
+gopkg.in/fsnotify.v1 v1.4.7/go.mod h1:Tz8NjZHkW78fSQdbUxIjBTcgA1z1m8ZHf0WmKUhAMys=
+gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7 h1:uRGJdciOHaEIrze2W8Q3AKkepLTh2hOroT7a+7czfdQ=
+gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7/go.mod h1:dt/ZhP58zS4L8KSrWDmTeBkI65Dw0HsyUHuEVlX15mw=
+gopkg.in/yaml.v2 v2.2.1 h1:mUhvW9EsL+naU5Q3cakzfE91YhliOondGd6ZrsDBHQE=
+gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=

vendor/github.com/golang/snappy/.gitignore

@@ -0,0 +1,16 @@
+cmd/snappytool/snappytool
+testdata/bench
+
+# These explicitly listed benchmark data files are for an obsolete version of
+# snappy_test.go.
+testdata/alice29.txt
+testdata/asyoulik.txt
+testdata/fireworks.jpeg
+testdata/geo.protodata
+testdata/html
+testdata/html_x_4
+testdata/kppkn.gtb
+testdata/lcet10.txt
+testdata/paper-100k.pdf
+testdata/plrabn12.txt
+testdata/urls.10K

vendor/github.com/golang/snappy/AUTHORS

@@ -0,0 +1,18 @@
+# This is the official list of Snappy-Go authors for copyright purposes.
+# This file is distinct from the CONTRIBUTORS files.
+# See the latter for an explanation.
+
+# Names should be added to this file as
+#	Name or Organization <email address>
+# The email address is not required for organizations.
+
+# Please keep the list sorted.
+
+Amazon.com, Inc
+Damian Gryski <dgryski@gmail.com>
+Eric Buth <eric@topos.com>
+Google Inc.
+Jan Mercl <0xjnml@gmail.com>
+Klaus Post <klauspost@gmail.com>
+Rodolfo Carvalho <rhcarvalho@gmail.com>
+Sebastien Binet <seb.binet@gmail.com>

vendor/github.com/golang/snappy/CONTRIBUTORS

@@ -0,0 +1,41 @@
+# This is the official list of people who can contribute
+# (and typically have contributed) code to the Snappy-Go repository.
+# The AUTHORS file lists the copyright holders; this file
+# lists people.  For example, Google employees are listed here
+# but not in AUTHORS, because Google holds the copyright.
+#
+# The submission process automatically checks to make sure
+# that people submitting code are listed in this file (by email address).
+#
+# Names should be added to this file only after verifying that
+# the individual or the individual's organization has agreed to
+# the appropriate Contributor License Agreement, found here:
+#
+#     http://code.google.com/legal/individual-cla-v1.0.html
+#     http://code.google.com/legal/corporate-cla-v1.0.html
+#
+# The agreement for individuals can be filled out on the web.
+#
+# When adding J Random Contributor's name to this file,
+# either J's name or J's organization's name should be
+# added to the AUTHORS file, depending on whether the
+# individual or corporate CLA was used.
+
+# Names should be added to this file like so:
+#     Name <email address>
+
+# Please keep the list sorted.
+
+Alex Legg <alexlegg@google.com>
+Damian Gryski <dgryski@gmail.com>
+Eric Buth <eric@topos.com>
+Jan Mercl <0xjnml@gmail.com>
+Jonathan Swinney <jswinney@amazon.com>
+Kai Backman <kaib@golang.org>
+Klaus Post <klauspost@gmail.com>
+Marc-Antoine Ruel <maruel@chromium.org>
+Nigel Tao <nigeltao@golang.org>
+Rob Pike <r@golang.org>
+Rodolfo Carvalho <rhcarvalho@gmail.com>
+Russ Cox <rsc@golang.org>
+Sebastien Binet <seb.binet@gmail.com>

vendor/github.com/golang/snappy/LICENSE

@@ -0,0 +1,27 @@
+Copyright (c) 2011 The Snappy-Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

vendor/github.com/golang/snappy/README

@@ -0,0 +1,107 @@
+The Snappy compression format in the Go programming language.
+
+To download and install from source:
+$ go get github.com/golang/snappy
+
+Unless otherwise noted, the Snappy-Go source files are distributed
+under the BSD-style license found in the LICENSE file.
+
+
+
+Benchmarks.
+
+The golang/snappy benchmarks include compressing (Z) and decompressing (U) ten
+or so files, the same set used by the C++ Snappy code (github.com/google/snappy
+and note the "google", not "golang"). On an "Intel(R) Core(TM) i7-3770 CPU @
+3.40GHz", Go's GOARCH=amd64 numbers as of 2016-05-29:
+
+"go test -test.bench=."
+
+_UFlat0-8         2.19GB/s ± 0%  html
+_UFlat1-8         1.41GB/s ± 0%  urls
+_UFlat2-8         23.5GB/s ± 2%  jpg
+_UFlat3-8         1.91GB/s ± 0%  jpg_200
+_UFlat4-8         14.0GB/s ± 1%  pdf
+_UFlat5-8         1.97GB/s ± 0%  html4
+_UFlat6-8          814MB/s ± 0%  txt1
+_UFlat7-8          785MB/s ± 0%  txt2
+_UFlat8-8          857MB/s ± 0%  txt3
+_UFlat9-8          719MB/s ± 1%  txt4
+_UFlat10-8        2.84GB/s ± 0%  pb
+_UFlat11-8        1.05GB/s ± 0%  gaviota
+
+_ZFlat0-8         1.04GB/s ± 0%  html
+_ZFlat1-8          534MB/s ± 0%  urls
+_ZFlat2-8         15.7GB/s ± 1%  jpg
+_ZFlat3-8          740MB/s ± 3%  jpg_200
+_ZFlat4-8         9.20GB/s ± 1%  pdf
+_ZFlat5-8          991MB/s ± 0%  html4
+_ZFlat6-8          379MB/s ± 0%  txt1
+_ZFlat7-8          352MB/s ± 0%  txt2
+_ZFlat8-8          396MB/s ± 1%  txt3
+_ZFlat9-8          327MB/s ± 1%  txt4
+_ZFlat10-8        1.33GB/s ± 1%  pb
+_ZFlat11-8         605MB/s ± 1%  gaviota
+
+
+
+"go test -test.bench=. -tags=noasm"
+
+_UFlat0-8          621MB/s ± 2%  html
+_UFlat1-8          494MB/s ± 1%  urls
+_UFlat2-8         23.2GB/s ± 1%  jpg
+_UFlat3-8         1.12GB/s ± 1%  jpg_200
+_UFlat4-8         4.35GB/s ± 1%  pdf
+_UFlat5-8          609MB/s ± 0%  html4
+_UFlat6-8          296MB/s ± 0%  txt1
+_UFlat7-8          288MB/s ± 0%  txt2
+_UFlat8-8          309MB/s ± 1%  txt3
+_UFlat9-8          280MB/s ± 1%  txt4
+_UFlat10-8         753MB/s ± 0%  pb
+_UFlat11-8         400MB/s ± 0%  gaviota
+
+_ZFlat0-8          409MB/s ± 1%  html
+_ZFlat1-8          250MB/s ± 1%  urls
+_ZFlat2-8         12.3GB/s ± 1%  jpg
+_ZFlat3-8          132MB/s ± 0%  jpg_200
+_ZFlat4-8         2.92GB/s ± 0%  pdf
+_ZFlat5-8          405MB/s ± 1%  html4
+_ZFlat6-8          179MB/s ± 1%  txt1
+_ZFlat7-8          170MB/s ± 1%  txt2
+_ZFlat8-8          189MB/s ± 1%  txt3
+_ZFlat9-8          164MB/s ± 1%  txt4
+_ZFlat10-8         479MB/s ± 1%  pb
+_ZFlat11-8         270MB/s ± 1%  gaviota
+
+
+
+For comparison (Go's encoded output is byte-for-byte identical to C++'s), here
+are the numbers from C++ Snappy's
+
+make CXXFLAGS="-O2 -DNDEBUG -g" clean snappy_unittest.log && cat snappy_unittest.log
+
+BM_UFlat/0     2.4GB/s  html
+BM_UFlat/1     1.4GB/s  urls
+BM_UFlat/2    21.8GB/s  jpg
+BM_UFlat/3     1.5GB/s  jpg_200
+BM_UFlat/4    13.3GB/s  pdf
+BM_UFlat/5     2.1GB/s  html4
+BM_UFlat/6     1.0GB/s  txt1
+BM_UFlat/7   959.4MB/s  txt2
+BM_UFlat/8     1.0GB/s  txt3
+BM_UFlat/9   864.5MB/s  txt4
+BM_UFlat/10    2.9GB/s  pb
+BM_UFlat/11    1.2GB/s  gaviota
+
+BM_ZFlat/0   944.3MB/s  html (22.31 %)
+BM_ZFlat/1   501.6MB/s  urls (47.78 %)
+BM_ZFlat/2    14.3GB/s  jpg (99.95 %)
+BM_ZFlat/3   538.3MB/s  jpg_200 (73.00 %)
+BM_ZFlat/4     8.3GB/s  pdf (83.30 %)
+BM_ZFlat/5   903.5MB/s  html4 (22.52 %)
+BM_ZFlat/6   336.0MB/s  txt1 (57.88 %)
+BM_ZFlat/7   312.3MB/s  txt2 (61.91 %)
+BM_ZFlat/8   353.1MB/s  txt3 (54.99 %)
+BM_ZFlat/9   289.9MB/s  txt4 (66.26 %)
+BM_ZFlat/10    1.2GB/s  pb (19.68 %)
+BM_ZFlat/11  527.4MB/s  gaviota (37.72 %)

vendor/github.com/golang/snappy/decode.go

@@ -0,0 +1,264 @@
+// Copyright 2011 The Snappy-Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package snappy
+
+import (
+	"encoding/binary"
+	"errors"
+	"io"
+)
+
+var (
+	// ErrCorrupt reports that the input is invalid.
+	ErrCorrupt = errors.New("snappy: corrupt input")
+	// ErrTooLarge reports that the uncompressed length is too large.
+	ErrTooLarge = errors.New("snappy: decoded block is too large")
+	// ErrUnsupported reports that the input isn't supported.
+	ErrUnsupported = errors.New("snappy: unsupported input")
+
+	errUnsupportedLiteralLength = errors.New("snappy: unsupported literal length")
+)
+
+// DecodedLen returns the length of the decoded block.
+func DecodedLen(src []byte) (int, error) {
+	v, _, err := decodedLen(src)
+	return v, err
+}
+
+// decodedLen returns the length of the decoded block and the number of bytes
+// that the length header occupied.
+func decodedLen(src []byte) (blockLen, headerLen int, err error) {
+	v, n := binary.Uvarint(src)
+	if n <= 0 || v > 0xffffffff {
+		return 0, 0, ErrCorrupt
+	}
+
+	const wordSize = 32 << (^uint(0) >> 32 & 1)
+	if wordSize == 32 && v > 0x7fffffff {
+		return 0, 0, ErrTooLarge
+	}
+	return int(v), n, nil
+}
+
+const (
+	decodeErrCodeCorrupt                  = 1
+	decodeErrCodeUnsupportedLiteralLength = 2
+)
+
+// Decode returns the decoded form of src. The returned slice may be a sub-
+// slice of dst if dst was large enough to hold the entire decoded block.
+// Otherwise, a newly allocated slice will be returned.
+//
+// The dst and src must not overlap. It is valid to pass a nil dst.
+//
+// Decode handles the Snappy block format, not the Snappy stream format.
+func Decode(dst, src []byte) ([]byte, error) {
+	dLen, s, err := decodedLen(src)
+	if err != nil {
+		return nil, err
+	}
+	if dLen <= len(dst) {
+		dst = dst[:dLen]
+	} else {
+		dst = make([]byte, dLen)
+	}
+	switch decode(dst, src[s:]) {
+	case 0:
+		return dst, nil
+	case decodeErrCodeUnsupportedLiteralLength:
+		return nil, errUnsupportedLiteralLength
+	}
+	return nil, ErrCorrupt
+}
+
+// NewReader returns a new Reader that decompresses from r, using the framing
+// format described at
+// https://github.com/google/snappy/blob/master/framing_format.txt
+func NewReader(r io.Reader) *Reader {
+	return &Reader{
+		r:       r,
+		decoded: make([]byte, maxBlockSize),
+		buf:     make([]byte, maxEncodedLenOfMaxBlockSize+checksumSize),
+	}
+}
+
+// Reader is an io.Reader that can read Snappy-compressed bytes.
+//
+// Reader handles the Snappy stream format, not the Snappy block format.
+type Reader struct {
+	r       io.Reader
+	err     error
+	decoded []byte
+	buf     []byte
+	// decoded[i:j] contains decoded bytes that have not yet been passed on.
+	i, j       int
+	readHeader bool
+}
+
+// Reset discards any buffered data, resets all state, and switches the Snappy
+// reader to read from r. This permits reusing a Reader rather than allocating
+// a new one.
+func (r *Reader) Reset(reader io.Reader) {
+	r.r = reader
+	r.err = nil
+	r.i = 0
+	r.j = 0
+	r.readHeader = false
+}
+
+func (r *Reader) readFull(p []byte, allowEOF bool) (ok bool) {
+	if _, r.err = io.ReadFull(r.r, p); r.err != nil {
+		if r.err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
+			r.err = ErrCorrupt
+		}
+		return false
+	}
+	return true
+}
+
+func (r *Reader) fill() error {
+	for r.i >= r.j {
+		if !r.readFull(r.buf[:4], true) {
+			return r.err
+		}
+		chunkType := r.buf[0]
+		if !r.readHeader {
+			if chunkType != chunkTypeStreamIdentifier {
+				r.err = ErrCorrupt
+				return r.err
+			}
+			r.readHeader = true
+		}
+		chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
+		if chunkLen > len(r.buf) {
+			r.err = ErrUnsupported
+			return r.err
+		}
+
+		// The chunk types are specified at
+		// https://github.com/google/snappy/blob/master/framing_format.txt
+		switch chunkType {
+		case chunkTypeCompressedData:
+			// Section 4.2. Compressed data (chunk type 0x00).
+			if chunkLen < checksumSize {
+				r.err = ErrCorrupt
+				return r.err
+			}
+			buf := r.buf[:chunkLen]
+			if !r.readFull(buf, false) {
+				return r.err
+			}
+			checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
+			buf = buf[checksumSize:]
+
+			n, err := DecodedLen(buf)
+			if err != nil {
+				r.err = err
+				return r.err
+			}
+			if n > len(r.decoded) {
+				r.err = ErrCorrupt
+				return r.err
+			}
+			if _, err := Decode(r.decoded, buf); err != nil {
+				r.err = err
+				return r.err
+			}
+			if crc(r.decoded[:n]) != checksum {
+				r.err = ErrCorrupt
+				return r.err
+			}
+			r.i, r.j = 0, n
+			continue
+
+		case chunkTypeUncompressedData:
+			// Section 4.3. Uncompressed data (chunk type 0x01).
+			if chunkLen < checksumSize {
+				r.err = ErrCorrupt
+				return r.err
+			}
+			buf := r.buf[:checksumSize]
+			if !r.readFull(buf, false) {
+				return r.err
+			}
+			checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
+			// Read directly into r.decoded instead of via r.buf.
+			n := chunkLen - checksumSize
+			if n > len(r.decoded) {
+				r.err = ErrCorrupt
+				return r.err
+			}
+			if !r.readFull(r.decoded[:n], false) {
+				return r.err
+			}
+			if crc(r.decoded[:n]) != checksum {
+				r.err = ErrCorrupt
+				return r.err
+			}
+			r.i, r.j = 0, n
+			continue
+
+		case chunkTypeStreamIdentifier:
+			// Section 4.1. Stream identifier (chunk type 0xff).
+			if chunkLen != len(magicBody) {
+				r.err = ErrCorrupt
+				return r.err
+			}
+			if !r.readFull(r.buf[:len(magicBody)], false) {
+				return r.err
+			}
+			for i := 0; i < len(magicBody); i++ {
+				if r.buf[i] != magicBody[i] {
+					r.err = ErrCorrupt
+					return r.err
+				}
+			}
+			continue
+		}
+
+		if chunkType <= 0x7f {
+			// Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f).
+			r.err = ErrUnsupported
+			return r.err
+		}
+		// Section 4.4 Padding (chunk type 0xfe).
+		// Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
+		if !r.readFull(r.buf[:chunkLen], false) {
+			return r.err
+		}
+	}
+
+	return nil
+}
+
+// Read satisfies the io.Reader interface.
+func (r *Reader) Read(p []byte) (int, error) {
+	if r.err != nil {
+		return 0, r.err
+	}
+
+	if err := r.fill(); err != nil {
+		return 0, err
+	}
+
+	n := copy(p, r.decoded[r.i:r.j])
+	r.i += n
+	return n, nil
+}
+
+// ReadByte satisfies the io.ByteReader interface.
+func (r *Reader) ReadByte() (byte, error) {
+	if r.err != nil {
+		return 0, r.err
+	}
+
+	if err := r.fill(); err != nil {
+		return 0, err
+	}
+
+	c := r.decoded[r.i]
+	r.i++
+	return c, nil
+}

vendor/github.com/golang/snappy/decode_amd64.s

@@ -0,0 +1,490 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !appengine
+// +build gc
+// +build !noasm
+
+#include "textflag.h"
+
+// The asm code generally follows the pure Go code in decode_other.go, except
+// where marked with a "!!!".
+
+// func decode(dst, src []byte) int
+//
+// All local variables fit into registers. The non-zero stack size is only to
+// spill registers and push args when issuing a CALL. The register allocation:
+//	- AX	scratch
+//	- BX	scratch
+//	- CX	length or x
+//	- DX	offset
+//	- SI	&src[s]
+//	- DI	&dst[d]
+//	+ R8	dst_base
+//	+ R9	dst_len
+//	+ R10	dst_base + dst_len
+//	+ R11	src_base
+//	+ R12	src_len
+//	+ R13	src_base + src_len
+//	- R14	used by doCopy
+//	- R15	used by doCopy
+//
+// The registers R8-R13 (marked with a "+") are set at the start of the
+// function, and after a CALL returns, and are not otherwise modified.
+//
+// The d variable is implicitly DI - R8,  and len(dst)-d is R10 - DI.
+// The s variable is implicitly SI - R11, and len(src)-s is R13 - SI.
+TEXT ·decode(SB), NOSPLIT, $48-56
+	// Initialize SI, DI and R8-R13.
+	MOVQ dst_base+0(FP), R8
+	MOVQ dst_len+8(FP), R9
+	MOVQ R8, DI
+	MOVQ R8, R10
+	ADDQ R9, R10
+	MOVQ src_base+24(FP), R11
+	MOVQ src_len+32(FP), R12
+	MOVQ R11, SI
+	MOVQ R11, R13
+	ADDQ R12, R13
+
+loop:
+	// for s < len(src)
+	CMPQ SI, R13
+	JEQ  end
+
+	// CX = uint32(src[s])
+	//
+	// switch src[s] & 0x03
+	MOVBLZX (SI), CX
+	MOVL    CX, BX
+	ANDL    $3, BX
+	CMPL    BX, $1
+	JAE     tagCopy
+
+	// ----------------------------------------
+	// The code below handles literal tags.
+
+	// case tagLiteral:
+	// x := uint32(src[s] >> 2)
+	// switch
+	SHRL $2, CX
+	CMPL CX, $60
+	JAE  tagLit60Plus
+
+	// case x < 60:
+	// s++
+	INCQ SI
+
+doLit:
+	// This is the end of the inner "switch", when we have a literal tag.
+	//
+	// We assume that CX == x and x fits in a uint32, where x is the variable
+	// used in the pure Go decode_other.go code.
+
+	// length = int(x) + 1
+	//
+	// Unlike the pure Go code, we don't need to check if length <= 0 because
+	// CX can hold 64 bits, so the increment cannot overflow.
+	INCQ CX
+
+	// Prepare to check if copying length bytes will run past the end of dst or
+	// src.
+	//
+	// AX = len(dst) - d
+	// BX = len(src) - s
+	MOVQ R10, AX
+	SUBQ DI, AX
+	MOVQ R13, BX
+	SUBQ SI, BX
+
+	// !!! Try a faster technique for short (16 or fewer bytes) copies.
+	//
+	// if length > 16 || len(dst)-d < 16 || len(src)-s < 16 {
+	//   goto callMemmove // Fall back on calling runtime·memmove.
+	// }
+	//
+	// The C++ snappy code calls this TryFastAppend. It also checks len(src)-s
+	// against 21 instead of 16, because it cannot assume that all of its input
+	// is contiguous in memory and so it needs to leave enough source bytes to
+	// read the next tag without refilling buffers, but Go's Decode assumes
+	// contiguousness (the src argument is a []byte).
+	CMPQ CX, $16
+	JGT  callMemmove
+	CMPQ AX, $16
+	JLT  callMemmove
+	CMPQ BX, $16
+	JLT  callMemmove
+
+	// !!! Implement the copy from src to dst as a 16-byte load and store.
+	// (Decode's documentation says that dst and src must not overlap.)
+	//
+	// This always copies 16 bytes, instead of only length bytes, but that's
+	// OK. If the input is a valid Snappy encoding then subsequent iterations
+	// will fix up the overrun. Otherwise, Decode returns a nil []byte (and a
+	// non-nil error), so the overrun will be ignored.
+	//
+	// Note that on amd64, it is legal and cheap to issue unaligned 8-byte or
+	// 16-byte loads and stores. This technique probably wouldn't be as
+	// effective on architectures that are fussier about alignment.
+	MOVOU 0(SI), X0
+	MOVOU X0, 0(DI)
+
+	// d += length
+	// s += length
+	ADDQ CX, DI
+	ADDQ CX, SI
+	JMP  loop
+
+callMemmove:
+	// if length > len(dst)-d || length > len(src)-s { etc }
+	CMPQ CX, AX
+	JGT  errCorrupt
+	CMPQ CX, BX
+	JGT  errCorrupt
+
+	// copy(dst[d:], src[s:s+length])
+	//
+	// This means calling runtime·memmove(&dst[d], &src[s], length), so we push
+	// DI, SI and CX as arguments. Coincidentally, we also need to spill those
+	// three registers to the stack, to save local variables across the CALL.
+	MOVQ DI, 0(SP)
+	MOVQ SI, 8(SP)
+	MOVQ CX, 16(SP)
+	MOVQ DI, 24(SP)
+	MOVQ SI, 32(SP)
+	MOVQ CX, 40(SP)
+	CALL runtime·memmove(SB)
+
+	// Restore local variables: unspill registers from the stack and
+	// re-calculate R8-R13.
+	MOVQ 24(SP), DI
+	MOVQ 32(SP), SI
+	MOVQ 40(SP), CX
+	MOVQ dst_base+0(FP), R8
+	MOVQ dst_len+8(FP), R9
+	MOVQ R8, R10
+	ADDQ R9, R10
+	MOVQ src_base+24(FP), R11
+	MOVQ src_len+32(FP), R12
+	MOVQ R11, R13
+	ADDQ R12, R13
+
+	// d += length
+	// s += length
+	ADDQ CX, DI
+	ADDQ CX, SI
+	JMP  loop
+
+tagLit60Plus:
+	// !!! This fragment does the
+	//
+	// s += x - 58; if uint(s) > uint(len(src)) { etc }
+	//
+	// checks. In the asm version, we code it once instead of once per switch case.
+	ADDQ CX, SI
+	SUBQ $58, SI
+	MOVQ SI, BX
+	SUBQ R11, BX
+	CMPQ BX, R12
+	JA   errCorrupt
+
+	// case x == 60:
+	CMPL CX, $61
+	JEQ  tagLit61
+	JA   tagLit62Plus
+
+	// x = uint32(src[s-1])
+	MOVBLZX -1(SI), CX
+	JMP     doLit
+
+tagLit61:
+	// case x == 61:
+	// x = uint32(src[s-2]) | uint32(src[s-1])<<8
+	MOVWLZX -2(SI), CX
+	JMP     doLit
+
+tagLit62Plus:
+	CMPL CX, $62
+	JA   tagLit63
+
+	// case x == 62:
+	// x = uint32(src[s-3]) | uint32(src[s-2])<<8 | uint32(src[s-1])<<16
+	MOVWLZX -3(SI), CX
+	MOVBLZX -1(SI), BX
+	SHLL    $16, BX
+	ORL     BX, CX
+	JMP     doLit
+
+tagLit63:
+	// case x == 63:
+	// x = uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24
+	MOVL -4(SI), CX
+	JMP  doLit
+
+// The code above handles literal tags.
+// ----------------------------------------
+// The code below handles copy tags.
+
+tagCopy4:
+	// case tagCopy4:
+	// s += 5
+	ADDQ $5, SI
+
+	// if uint(s) > uint(len(src)) { etc }
+	MOVQ SI, BX
+	SUBQ R11, BX
+	CMPQ BX, R12
+	JA   errCorrupt
+
+	// length = 1 + int(src[s-5])>>2
+	SHRQ $2, CX
+	INCQ CX
+
+	// offset = int(uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24)
+	MOVLQZX -4(SI), DX
+	JMP     doCopy
+
+tagCopy2:
+	// case tagCopy2:
+	// s += 3
+	ADDQ $3, SI
+
+	// if uint(s) > uint(len(src)) { etc }
+	MOVQ SI, BX
+	SUBQ R11, BX
+	CMPQ BX, R12
+	JA   errCorrupt
+
+	// length = 1 + int(src[s-3])>>2
+	SHRQ $2, CX
+	INCQ CX
+
+	// offset = int(uint32(src[s-2]) | uint32(src[s-1])<<8)
+	MOVWQZX -2(SI), DX
+	JMP     doCopy
+
+tagCopy:
+	// We have a copy tag. We assume that:
+	//	- BX == src[s] & 0x03
+	//	- CX == src[s]
+	CMPQ BX, $2
+	JEQ  tagCopy2
+	JA   tagCopy4
+
+	// case tagCopy1:
+	// s += 2
+	ADDQ $2, SI
+
+	// if uint(s) > uint(len(src)) { etc }
+	MOVQ SI, BX
+	SUBQ R11, BX
+	CMPQ BX, R12
+	JA   errCorrupt
+
+	// offset = int(uint32(src[s-2])&0xe0<<3 | uint32(src[s-1]))
+	MOVQ    CX, DX
+	ANDQ    $0xe0, DX
+	SHLQ    $3, DX
+	MOVBQZX -1(SI), BX
+	ORQ     BX, DX
+
+	// length = 4 + int(src[s-2])>>2&0x7
+	SHRQ $2, CX
+	ANDQ $7, CX
+	ADDQ $4, CX
+
+doCopy:
+	// This is the end of the outer "switch", when we have a copy tag.
+	//
+	// We assume that:
+	//	- CX == length && CX > 0
+	//	- DX == offset
+
+	// if offset <= 0 { etc }
+	CMPQ DX, $0
+	JLE  errCorrupt
+
+	// if d < offset { etc }
+	MOVQ DI, BX
+	SUBQ R8, BX
+	CMPQ BX, DX
+	JLT  errCorrupt
+
+	// if length > len(dst)-d { etc }
+	MOVQ R10, BX
+	SUBQ DI, BX
+	CMPQ CX, BX
+	JGT  errCorrupt
+
+	// forwardCopy(dst[d:d+length], dst[d-offset:]); d += length
+	//
+	// Set:
+	//	- R14 = len(dst)-d
+	//	- R15 = &dst[d-offset]
+	MOVQ R10, R14
+	SUBQ DI, R14
+	MOVQ DI, R15
+	SUBQ DX, R15
+
+	// !!! Try a faster technique for short (16 or fewer bytes) forward copies.
+	//
+	// First, try using two 8-byte load/stores, similar to the doLit technique
+	// above. Even if dst[d:d+length] and dst[d-offset:] can overlap, this is
+	// still OK if offset >= 8. Note that this has to be two 8-byte load/stores
+	// and not one 16-byte load/store, and the first store has to be before the
+	// second load, due to the overlap if offset is in the range [8, 16).
+	//
+	// if length > 16 || offset < 8 || len(dst)-d < 16 {
+	//   goto slowForwardCopy
+	// }
+	// copy 16 bytes
+	// d += length
+	CMPQ CX, $16
+	JGT  slowForwardCopy
+	CMPQ DX, $8
+	JLT  slowForwardCopy
+	CMPQ R14, $16
+	JLT  slowForwardCopy
+	MOVQ 0(R15), AX
+	MOVQ AX, 0(DI)
+	MOVQ 8(R15), BX
+	MOVQ BX, 8(DI)
+	ADDQ CX, DI
+	JMP  loop
+
+slowForwardCopy:
+	// !!! If the forward copy is longer than 16 bytes, or if offset < 8, we
+	// can still try 8-byte load stores, provided we can overrun up to 10 extra
+	// bytes. As above, the overrun will be fixed up by subsequent iterations
+	// of the outermost loop.
+	//
+	// The C++ snappy code calls this technique IncrementalCopyFastPath. Its
+	// commentary says:
+	//
+	// ----
+	//
+	// The main part of this loop is a simple copy of eight bytes at a time
+	// until we've copied (at least) the requested amount of bytes.  However,
+	// if d and d-offset are less than eight bytes apart (indicating a
+	// repeating pattern of length < 8), we first need to expand the pattern in
+	// order to get the correct results. For instance, if the buffer looks like
+	// this, with the eight-byte <d-offset> and <d> patterns marked as
+	// intervals:
+	//
+	//    abxxxxxxxxxxxx
+	//    [------]           d-offset
+	//      [------]         d
+	//
+	// a single eight-byte copy from <d-offset> to <d> will repeat the pattern
+	// once, after which we can move <d> two bytes without moving <d-offset>:
+	//
+	//    ababxxxxxxxxxx
+	//    [------]           d-offset
+	//        [------]       d
+	//
+	// and repeat the exercise until the two no longer overlap.
+	//
+	// This allows us to do very well in the special case of one single byte
+	// repeated many times, without taking a big hit for more general cases.
+	//
+	// The worst case of extra writing past the end of the match occurs when
+	// offset == 1 and length == 1; the last copy will read from byte positions
+	// [0..7] and write to [4..11], whereas it was only supposed to write to
+	// position 1. Thus, ten excess bytes.
+	//
+	// ----
+	//
+	// That "10 byte overrun" worst case is confirmed by Go's
+	// TestSlowForwardCopyOverrun, which also tests the fixUpSlowForwardCopy
+	// and finishSlowForwardCopy algorithm.
+	//
+	// if length > len(dst)-d-10 {
+	//   goto verySlowForwardCopy
+	// }
+	SUBQ $10, R14
+	CMPQ CX, R14
+	JGT  verySlowForwardCopy
+
+makeOffsetAtLeast8:
+	// !!! As above, expand the pattern so that offset >= 8 and we can use
+	// 8-byte load/stores.
+	//
+	// for offset < 8 {
+	//   copy 8 bytes from dst[d-offset:] to dst[d:]
+	//   length -= offset
+	//   d      += offset
+	//   offset += offset
+	//   // The two previous lines together means that d-offset, and therefore
+	//   // R15, is unchanged.
+	// }
+	CMPQ DX, $8
+	JGE  fixUpSlowForwardCopy
+	MOVQ (R15), BX
+	MOVQ BX, (DI)
+	SUBQ DX, CX
+	ADDQ DX, DI
+	ADDQ DX, DX
+	JMP  makeOffsetAtLeast8
+
+fixUpSlowForwardCopy:
+	// !!! Add length (which might be negative now) to d (implied by DI being
+	// &dst[d]) so that d ends up at the right place when we jump back to the
+	// top of the loop. Before we do that, though, we save DI to AX so that, if
+	// length is positive, copying the remaining length bytes will write to the
+	// right place.
+	MOVQ DI, AX
+	ADDQ CX, DI
+
+finishSlowForwardCopy:
+	// !!! Repeat 8-byte load/stores until length <= 0. Ending with a negative
+	// length means that we overrun, but as above, that will be fixed up by
+	// subsequent iterations of the outermost loop.
+	CMPQ CX, $0
+	JLE  loop
+	MOVQ (R15), BX
+	MOVQ BX, (AX)
+	ADDQ $8, R15
+	ADDQ $8, AX
+	SUBQ $8, CX
+	JMP  finishSlowForwardCopy
+
+verySlowForwardCopy:
+	// verySlowForwardCopy is a simple implementation of forward copy. In C
+	// parlance, this is a do/while loop instead of a while loop, since we know
+	// that length > 0. In Go syntax:
+	//
+	// for {
+	//   dst[d] = dst[d - offset]
+	//   d++
+	//   length--
+	//   if length == 0 {
+	//     break
+	//   }
+	// }
+	MOVB (R15), BX
+	MOVB BX, (DI)
+	INCQ R15
+	INCQ DI
+	DECQ CX
+	JNZ  verySlowForwardCopy
+	JMP  loop
+
+// The code above handles copy tags.
+// ----------------------------------------
+
+end:
+	// This is the end of the "for s < len(src)".
+	//
+	// if d != len(dst) { etc }
+	CMPQ DI, R10
+	JNE  errCorrupt
+
+	// return 0
+	MOVQ $0, ret+48(FP)
+	RET
+
+errCorrupt:
+	// return decodeErrCodeCorrupt
+	MOVQ $1, ret+48(FP)
+	RET

vendor/github.com/golang/snappy/decode_arm64.s

@@ -0,0 +1,494 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !appengine
+// +build gc
+// +build !noasm
+
+#include "textflag.h"
+
+// The asm code generally follows the pure Go code in decode_other.go, except
+// where marked with a "!!!".
+
+// func decode(dst, src []byte) int
+//
+// All local variables fit into registers. The non-zero stack size is only to
+// spill registers and push args when issuing a CALL. The register allocation:
+//	- R2	scratch
+//	- R3	scratch
+//	- R4	length or x
+//	- R5	offset
+//	- R6	&src[s]
+//	- R7	&dst[d]
+//	+ R8	dst_base
+//	+ R9	dst_len
+//	+ R10	dst_base + dst_len
+//	+ R11	src_base
+//	+ R12	src_len
+//	+ R13	src_base + src_len
+//	- R14	used by doCopy
+//	- R15	used by doCopy
+//
+// The registers R8-R13 (marked with a "+") are set at the start of the
+// function, and after a CALL returns, and are not otherwise modified.
+//
+// The d variable is implicitly R7 - R8,  and len(dst)-d is R10 - R7.
+// The s variable is implicitly R6 - R11, and len(src)-s is R13 - R6.
+TEXT ·decode(SB), NOSPLIT, $56-56
+	// Initialize R6, R7 and R8-R13.
+	MOVD dst_base+0(FP), R8
+	MOVD dst_len+8(FP), R9
+	MOVD R8, R7
+	MOVD R8, R10
+	ADD  R9, R10, R10
+	MOVD src_base+24(FP), R11
+	MOVD src_len+32(FP), R12
+	MOVD R11, R6
+	MOVD R11, R13
+	ADD  R12, R13, R13
+
+loop:
+	// for s < len(src)
+	CMP R13, R6
+	BEQ end
+
+	// R4 = uint32(src[s])
+	//
+	// switch src[s] & 0x03
+	MOVBU (R6), R4
+	MOVW  R4, R3
+	ANDW  $3, R3
+	MOVW  $1, R1
+	CMPW  R1, R3
+	BGE   tagCopy
+
+	// ----------------------------------------
+	// The code below handles literal tags.
+
+	// case tagLiteral:
+	// x := uint32(src[s] >> 2)
+	// switch
+	MOVW $60, R1
+	LSRW $2, R4, R4
+	CMPW R4, R1
+	BLS  tagLit60Plus
+
+	// case x < 60:
+	// s++
+	ADD $1, R6, R6
+
+doLit:
+	// This is the end of the inner "switch", when we have a literal tag.
+	//
+	// We assume that R4 == x and x fits in a uint32, where x is the variable
+	// used in the pure Go decode_other.go code.
+
+	// length = int(x) + 1
+	//
+	// Unlike the pure Go code, we don't need to check if length <= 0 because
+	// R4 can hold 64 bits, so the increment cannot overflow.
+	ADD $1, R4, R4
+
+	// Prepare to check if copying length bytes will run past the end of dst or
+	// src.
+	//
+	// R2 = len(dst) - d
+	// R3 = len(src) - s
+	MOVD R10, R2
+	SUB  R7, R2, R2
+	MOVD R13, R3
+	SUB  R6, R3, R3
+
+	// !!! Try a faster technique for short (16 or fewer bytes) copies.
+	//
+	// if length > 16 || len(dst)-d < 16 || len(src)-s < 16 {
+	//   goto callMemmove // Fall back on calling runtime·memmove.
+	// }
+	//
+	// The C++ snappy code calls this TryFastAppend. It also checks len(src)-s
+	// against 21 instead of 16, because it cannot assume that all of its input
+	// is contiguous in memory and so it needs to leave enough source bytes to
+	// read the next tag without refilling buffers, but Go's Decode assumes
+	// contiguousness (the src argument is a []byte).
+	CMP $16, R4
+	BGT callMemmove
+	CMP $16, R2
+	BLT callMemmove
+	CMP $16, R3
+	BLT callMemmove
+
+	// !!! Implement the copy from src to dst as a 16-byte load and store.
+	// (Decode's documentation says that dst and src must not overlap.)
+	//
+	// This always copies 16 bytes, instead of only length bytes, but that's
+	// OK. If the input is a valid Snappy encoding then subsequent iterations
+	// will fix up the overrun. Otherwise, Decode returns a nil []byte (and a
+	// non-nil error), so the overrun will be ignored.
+	//
+	// Note that on arm64, it is legal and cheap to issue unaligned 8-byte or
+	// 16-byte loads and stores. This technique probably wouldn't be as
+	// effective on architectures that are fussier about alignment.
+	LDP 0(R6), (R14, R15)
+	STP (R14, R15), 0(R7)
+
+	// d += length
+	// s += length
+	ADD R4, R7, R7
+	ADD R4, R6, R6
+	B   loop
+
+callMemmove:
+	// if length > len(dst)-d || length > len(src)-s { etc }
+	CMP R2, R4
+	BGT errCorrupt
+	CMP R3, R4
+	BGT errCorrupt
+
+	// copy(dst[d:], src[s:s+length])
+	//
+	// This means calling runtime·memmove(&dst[d], &src[s], length), so we push
+	// R7, R6 and R4 as arguments. Coincidentally, we also need to spill those
+	// three registers to the stack, to save local variables across the CALL.
+	MOVD R7, 8(RSP)
+	MOVD R6, 16(RSP)
+	MOVD R4, 24(RSP)
+	MOVD R7, 32(RSP)
+	MOVD R6, 40(RSP)
+	MOVD R4, 48(RSP)
+	CALL runtime·memmove(SB)
+
+	// Restore local variables: unspill registers from the stack and
+	// re-calculate R8-R13.
+	MOVD 32(RSP), R7
+	MOVD 40(RSP), R6
+	MOVD 48(RSP), R4
+	MOVD dst_base+0(FP), R8
+	MOVD dst_len+8(FP), R9
+	MOVD R8, R10
+	ADD  R9, R10, R10
+	MOVD src_base+24(FP), R11
+	MOVD src_len+32(FP), R12
+	MOVD R11, R13
+	ADD  R12, R13, R13
+
+	// d += length
+	// s += length
+	ADD R4, R7, R7
+	ADD R4, R6, R6
+	B   loop
+
+tagLit60Plus:
+	// !!! This fragment does the
+	//
+	// s += x - 58; if uint(s) > uint(len(src)) { etc }
+	//
+	// checks. In the asm version, we code it once instead of once per switch case.
+	ADD  R4, R6, R6
+	SUB  $58, R6, R6
+	MOVD R6, R3
+	SUB  R11, R3, R3
+	CMP  R12, R3
+	BGT  errCorrupt
+
+	// case x == 60:
+	MOVW $61, R1
+	CMPW R1, R4
+	BEQ  tagLit61
+	BGT  tagLit62Plus
+
+	// x = uint32(src[s-1])
+	MOVBU -1(R6), R4
+	B     doLit
+
+tagLit61:
+	// case x == 61:
+	// x = uint32(src[s-2]) | uint32(src[s-1])<<8
+	MOVHU -2(R6), R4
+	B     doLit
+
+tagLit62Plus:
+	CMPW $62, R4
+	BHI  tagLit63
+
+	// case x == 62:
+	// x = uint32(src[s-3]) | uint32(src[s-2])<<8 | uint32(src[s-1])<<16
+	MOVHU -3(R6), R4
+	MOVBU -1(R6), R3
+	ORR   R3<<16, R4
+	B     doLit
+
+tagLit63:
+	// case x == 63:
+	// x = uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24
+	MOVWU -4(R6), R4
+	B     doLit
+
+	// The code above handles literal tags.
+	// ----------------------------------------
+	// The code below handles copy tags.
+
+tagCopy4:
+	// case tagCopy4:
+	// s += 5
+	ADD $5, R6, R6
+
+	// if uint(s) > uint(len(src)) { etc }
+	MOVD R6, R3
+	SUB  R11, R3, R3
+	CMP  R12, R3
+	BGT  errCorrupt
+
+	// length = 1 + int(src[s-5])>>2
+	MOVD $1, R1
+	ADD  R4>>2, R1, R4
+
+	// offset = int(uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24)
+	MOVWU -4(R6), R5
+	B     doCopy
+
+tagCopy2:
+	// case tagCopy2:
+	// s += 3
+	ADD $3, R6, R6
+
+	// if uint(s) > uint(len(src)) { etc }
+	MOVD R6, R3
+	SUB  R11, R3, R3
+	CMP  R12, R3
+	BGT  errCorrupt
+
+	// length = 1 + int(src[s-3])>>2
+	MOVD $1, R1
+	ADD  R4>>2, R1, R4
+
+	// offset = int(uint32(src[s-2]) | uint32(src[s-1])<<8)
+	MOVHU -2(R6), R5
+	B     doCopy
+
+tagCopy:
+	// We have a copy tag. We assume that:
+	//	- R3 == src[s] & 0x03
+	//	- R4 == src[s]
+	CMP $2, R3
+	BEQ tagCopy2
+	BGT tagCopy4
+
+	// case tagCopy1:
+	// s += 2
+	ADD $2, R6, R6
+
+	// if uint(s) > uint(len(src)) { etc }
+	MOVD R6, R3
+	SUB  R11, R3, R3
+	CMP  R12, R3
+	BGT  errCorrupt
+
+	// offset = int(uint32(src[s-2])&0xe0<<3 | uint32(src[s-1]))
+	MOVD  R4, R5
+	AND   $0xe0, R5
+	MOVBU -1(R6), R3
+	ORR   R5<<3, R3, R5
+
+	// length = 4 + int(src[s-2])>>2&0x7
+	MOVD $7, R1
+	AND  R4>>2, R1, R4
+	ADD  $4, R4, R4
+
+doCopy:
+	// This is the end of the outer "switch", when we have a copy tag.
+	//
+	// We assume that:
+	//	- R4 == length && R4 > 0
+	//	- R5 == offset
+
+	// if offset <= 0 { etc }
+	MOVD $0, R1
+	CMP  R1, R5
+	BLE  errCorrupt
+
+	// if d < offset { etc }
+	MOVD R7, R3
+	SUB  R8, R3, R3
+	CMP  R5, R3
+	BLT  errCorrupt
+
+	// if length > len(dst)-d { etc }
+	MOVD R10, R3
+	SUB  R7, R3, R3
+	CMP  R3, R4
+	BGT  errCorrupt
+
+	// forwardCopy(dst[d:d+length], dst[d-offset:]); d += length
+	//
+	// Set:
+	//	- R14 = len(dst)-d
+	//	- R15 = &dst[d-offset]
+	MOVD R10, R14
+	SUB  R7, R14, R14
+	MOVD R7, R15
+	SUB  R5, R15, R15
+
+	// !!! Try a faster technique for short (16 or fewer bytes) forward copies.
+	//
+	// First, try using two 8-byte load/stores, similar to the doLit technique
+	// above. Even if dst[d:d+length] and dst[d-offset:] can overlap, this is
+	// still OK if offset >= 8. Note that this has to be two 8-byte load/stores
+	// and not one 16-byte load/store, and the first store has to be before the
+	// second load, due to the overlap if offset is in the range [8, 16).
+	//
+	// if length > 16 || offset < 8 || len(dst)-d < 16 {
+	//   goto slowForwardCopy
+	// }
+	// copy 16 bytes
+	// d += length
+	CMP  $16, R4
+	BGT  slowForwardCopy
+	CMP  $8, R5
+	BLT  slowForwardCopy
+	CMP  $16, R14
+	BLT  slowForwardCopy
+	MOVD 0(R15), R2
+	MOVD R2, 0(R7)
+	MOVD 8(R15), R3
+	MOVD R3, 8(R7)
+	ADD  R4, R7, R7
+	B    loop
+
+slowForwardCopy:
+	// !!! If the forward copy is longer than 16 bytes, or if offset < 8, we
+	// can still try 8-byte load stores, provided we can overrun up to 10 extra
+	// bytes. As above, the overrun will be fixed up by subsequent iterations
+	// of the outermost loop.
+	//
+	// The C++ snappy code calls this technique IncrementalCopyFastPath. Its
+	// commentary says:
+	//
+	// ----
+	//
+	// The main part of this loop is a simple copy of eight bytes at a time
+	// until we've copied (at least) the requested amount of bytes.  However,
+	// if d and d-offset are less than eight bytes apart (indicating a
+	// repeating pattern of length < 8), we first need to expand the pattern in
+	// order to get the correct results. For instance, if the buffer looks like
+	// this, with the eight-byte <d-offset> and <d> patterns marked as
+	// intervals:
+	//
+	//    abxxxxxxxxxxxx
+	//    [------]           d-offset
+	//      [------]         d
+	//
+	// a single eight-byte copy from <d-offset> to <d> will repeat the pattern
+	// once, after which we can move <d> two bytes without moving <d-offset>:
+	//
+	//    ababxxxxxxxxxx
+	//    [------]           d-offset
+	//        [------]       d
+	//
+	// and repeat the exercise until the two no longer overlap.
+	//
+	// This allows us to do very well in the special case of one single byte
+	// repeated many times, without taking a big hit for more general cases.
+	//
+	// The worst case of extra writing past the end of the match occurs when
+	// offset == 1 and length == 1; the last copy will read from byte positions
+	// [0..7] and write to [4..11], whereas it was only supposed to write to
+	// position 1. Thus, ten excess bytes.
+	//
+	// ----
+	//
+	// That "10 byte overrun" worst case is confirmed by Go's
+	// TestSlowForwardCopyOverrun, which also tests the fixUpSlowForwardCopy
+	// and finishSlowForwardCopy algorithm.
+	//
+	// if length > len(dst)-d-10 {
+	//   goto verySlowForwardCopy
+	// }
+	SUB $10, R14, R14
+	CMP R14, R4
+	BGT verySlowForwardCopy
+
+makeOffsetAtLeast8:
+	// !!! As above, expand the pattern so that offset >= 8 and we can use
+	// 8-byte load/stores.
+	//
+	// for offset < 8 {
+	//   copy 8 bytes from dst[d-offset:] to dst[d:]
+	//   length -= offset
+	//   d      += offset
+	//   offset += offset
+	//   // The two previous lines together means that d-offset, and therefore
+	//   // R15, is unchanged.
+	// }
+	CMP  $8, R5
+	BGE  fixUpSlowForwardCopy
+	MOVD (R15), R3
+	MOVD R3, (R7)
+	SUB  R5, R4, R4
+	ADD  R5, R7, R7
+	ADD  R5, R5, R5
+	B    makeOffsetAtLeast8
+
+fixUpSlowForwardCopy:
+	// !!! Add length (which might be negative now) to d (implied by R7 being
+	// &dst[d]) so that d ends up at the right place when we jump back to the
+	// top of the loop. Before we do that, though, we save R7 to R2 so that, if
+	// length is positive, copying the remaining length bytes will write to the
+	// right place.
+	MOVD R7, R2
+	ADD  R4, R7, R7
+
+finishSlowForwardCopy:
+	// !!! Repeat 8-byte load/stores until length <= 0. Ending with a negative
+	// length means that we overrun, but as above, that will be fixed up by
+	// subsequent iterations of the outermost loop.
+	MOVD $0, R1
+	CMP  R1, R4
+	BLE  loop
+	MOVD (R15), R3
+	MOVD R3, (R2)
+	ADD  $8, R15, R15
+	ADD  $8, R2, R2
+	SUB  $8, R4, R4
+	B    finishSlowForwardCopy
+
+verySlowForwardCopy:
+	// verySlowForwardCopy is a simple implementation of forward copy. In C
+	// parlance, this is a do/while loop instead of a while loop, since we know
+	// that length > 0. In Go syntax:
+	//
+	// for {
+	//   dst[d] = dst[d - offset]
+	//   d++
+	//   length--
+	//   if length == 0 {
+	//     break
+	//   }
+	// }
+	MOVB (R15), R3
+	MOVB R3, (R7)
+	ADD  $1, R15, R15
+	ADD  $1, R7, R7
+	SUB  $1, R4, R4
+	CBNZ R4, verySlowForwardCopy
+	B    loop
+
+	// The code above handles copy tags.
+	// ----------------------------------------
+
+end:
+	// This is the end of the "for s < len(src)".
+	//
+	// if d != len(dst) { etc }
+	CMP R10, R7
+	BNE errCorrupt
+
+	// return 0
+	MOVD $0, ret+48(FP)
+	RET
+
+errCorrupt:
+	// return decodeErrCodeCorrupt
+	MOVD $1, R2
+	MOVD R2, ret+48(FP)
+	RET

vendor/github.com/golang/snappy/decode_asm.go

@@ -0,0 +1,15 @@
+// Copyright 2016 The Snappy-Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !appengine
+// +build gc
+// +build !noasm
+// +build amd64 arm64
+
+package snappy
+
+// decode has the same semantics as in decode_other.go.
+//
+//go:noescape
+func decode(dst, src []byte) int

vendor/github.com/golang/snappy/decode_other.go

@@ -0,0 +1,115 @@
+// Copyright 2016 The Snappy-Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !amd64,!arm64 appengine !gc noasm
+
+package snappy
+
+// decode writes the decoding of src to dst. It assumes that the varint-encoded
+// length of the decompressed bytes has already been read, and that len(dst)
+// equals that length.
+//
+// It returns 0 on success or a decodeErrCodeXxx error code on failure.
+func decode(dst, src []byte) int {
+	var d, s, offset, length int
+	for s < len(src) {
+		switch src[s] & 0x03 {
+		case tagLiteral:
+			x := uint32(src[s] >> 2)
+			switch {
+			case x < 60:
+				s++
+			case x == 60:
+				s += 2
+				if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
+					return decodeErrCodeCorrupt
+				}
+				x = uint32(src[s-1])
+			case x == 61:
+				s += 3
+				if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
+					return decodeErrCodeCorrupt
+				}
+				x = uint32(src[s-2]) | uint32(src[s-1])<<8
+			case x == 62:
+				s += 4
+				if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
+					return decodeErrCodeCorrupt
+				}
+				x = uint32(src[s-3]) | uint32(src[s-2])<<8 | uint32(src[s-1])<<16
+			case x == 63:
+				s += 5
+				if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
+					return decodeErrCodeCorrupt
+				}
+				x = uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24
+			}
+			length = int(x) + 1
+			if length <= 0 {
+				return decodeErrCodeUnsupportedLiteralLength
+			}
+			if length > len(dst)-d || length > len(src)-s {
+				return decodeErrCodeCorrupt
+			}
+			copy(dst[d:], src[s:s+length])
+			d += length
+			s += length
+			continue
+
+		case tagCopy1:
+			s += 2
+			if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
+				return decodeErrCodeCorrupt
+			}
+			length = 4 + int(src[s-2])>>2&0x7
+			offset = int(uint32(src[s-2])&0xe0<<3 | uint32(src[s-1]))
+
+		case tagCopy2:
+			s += 3
+			if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
+				return decodeErrCodeCorrupt
+			}
+			length = 1 + int(src[s-3])>>2
+			offset = int(uint32(src[s-2]) | uint32(src[s-1])<<8)
+
+		case tagCopy4:
+			s += 5
+			if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
+				return decodeErrCodeCorrupt
+			}
+			length = 1 + int(src[s-5])>>2
+			offset = int(uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24)
+		}
+
+		if offset <= 0 || d < offset || length > len(dst)-d {
+			return decodeErrCodeCorrupt
+		}
+		// Copy from an earlier sub-slice of dst to a later sub-slice.
+		// If no overlap, use the built-in copy:
+		if offset >= length {
+			copy(dst[d:d+length], dst[d-offset:])
+			d += length
+			continue
+		}
+
+		// Unlike the built-in copy function, this byte-by-byte copy always runs
+		// forwards, even if the slices overlap. Conceptually, this is:
+		//
+		// d += forwardCopy(dst[d:d+length], dst[d-offset:])
+		//
+		// We align the slices into a and b and show the compiler they are the same size.
+		// This allows the loop to run without bounds checks.
+		a := dst[d : d+length]
+		b := dst[d-offset:]
+		b = b[:len(a)]
+		for i := range a {
+			a[i] = b[i]
+		}
+		d += length
+	}
+	if d != len(dst) {
+		return decodeErrCodeCorrupt
+	}
+	return 0
+}

vendor/github.com/golang/snappy/encode.go

@@ -0,0 +1,289 @@
+// Copyright 2011 The Snappy-Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package snappy
+
+import (
+	"encoding/binary"
+	"errors"
+	"io"
+)
+
+// Encode returns the encoded form of src. The returned slice may be a sub-
+// slice of dst if dst was large enough to hold the entire encoded block.
+// Otherwise, a newly allocated slice will be returned.
+//
+// The dst and src must not overlap. It is valid to pass a nil dst.
+//
+// Encode handles the Snappy block format, not the Snappy stream format.
+func Encode(dst, src []byte) []byte {
+	if n := MaxEncodedLen(len(src)); n < 0 {
+		panic(ErrTooLarge)
+	} else if len(dst) < n {
+		dst = make([]byte, n)
+	}
+
+	// The block starts with the varint-encoded length of the decompressed bytes.
+	d := binary.PutUvarint(dst, uint64(len(src)))
+
+	for len(src) > 0 {
+		p := src
+		src = nil
+		if len(p) > maxBlockSize {
+			p, src = p[:maxBlockSize], p[maxBlockSize:]
+		}
+		if len(p) < minNonLiteralBlockSize {
+			d += emitLiteral(dst[d:], p)
+		} else {
+			d += encodeBlock(dst[d:], p)
+		}
+	}
+	return dst[:d]
+}
+
+// inputMargin is the minimum number of extra input bytes to keep, inside
+// encodeBlock's inner loop. On some architectures, this margin lets us
+// implement a fast path for emitLiteral, where the copy of short (<= 16 byte)
+// literals can be implemented as a single load to and store from a 16-byte
+// register. That literal's actual length can be as short as 1 byte, so this
+// can copy up to 15 bytes too much, but that's OK as subsequent iterations of
+// the encoding loop will fix up the copy overrun, and this inputMargin ensures
+// that we don't overrun the dst and src buffers.
+const inputMargin = 16 - 1
+
+// minNonLiteralBlockSize is the minimum size of the input to encodeBlock that
+// could be encoded with a copy tag. This is the minimum with respect to the
+// algorithm used by encodeBlock, not a minimum enforced by the file format.
+//
+// The encoded output must start with at least a 1 byte literal, as there are
+// no previous bytes to copy. A minimal (1 byte) copy after that, generated
+// from an emitCopy call in encodeBlock's main loop, would require at least
+// another inputMargin bytes, for the reason above: we want any emitLiteral
+// calls inside encodeBlock's main loop to use the fast path if possible, which
+// requires being able to overrun by inputMargin bytes. Thus,
+// minNonLiteralBlockSize equals 1 + 1 + inputMargin.
+//
+// The C++ code doesn't use this exact threshold, but it could, as discussed at
+// https://groups.google.com/d/topic/snappy-compression/oGbhsdIJSJ8/discussion
+// The difference between Go (2+inputMargin) and C++ (inputMargin) is purely an
+// optimization. It should not affect the encoded form. This is tested by
+// TestSameEncodingAsCppShortCopies.
+const minNonLiteralBlockSize = 1 + 1 + inputMargin
+
+// MaxEncodedLen returns the maximum length of a snappy block, given its
+// uncompressed length.
+//
+// It will return a negative value if srcLen is too large to encode.
+func MaxEncodedLen(srcLen int) int {
+	n := uint64(srcLen)
+	if n > 0xffffffff {
+		return -1
+	}
+	// Compressed data can be defined as:
+	//    compressed := item* literal*
+	//    item       := literal* copy
+	//
+	// The trailing literal sequence has a space blowup of at most 62/60
+	// since a literal of length 60 needs one tag byte + one extra byte
+	// for length information.
+	//
+	// Item blowup is trickier to measure. Suppose the "copy" op copies
+	// 4 bytes of data. Because of a special check in the encoding code,
+	// we produce a 4-byte copy only if the offset is < 65536. Therefore
+	// the copy op takes 3 bytes to encode, and this type of item leads
+	// to at most the 62/60 blowup for representing literals.
+	//
+	// Suppose the "copy" op copies 5 bytes of data. If the offset is big
+	// enough, it will take 5 bytes to encode the copy op. Therefore the
+	// worst case here is a one-byte literal followed by a five-byte copy.
+	// That is, 6 bytes of input turn into 7 bytes of "compressed" data.
+	//
+	// This last factor dominates the blowup, so the final estimate is:
+	n = 32 + n + n/6
+	if n > 0xffffffff {
+		return -1
+	}
+	return int(n)
+}
+
+var errClosed = errors.New("snappy: Writer is closed")
+
+// NewWriter returns a new Writer that compresses to w.
+//
+// The Writer returned does not buffer writes. There is no need to Flush or
+// Close such a Writer.
+//
+// Deprecated: the Writer returned is not suitable for many small writes, only
+// for few large writes. Use NewBufferedWriter instead, which is efficient
+// regardless of the frequency and shape of the writes, and remember to Close
+// that Writer when done.
+func NewWriter(w io.Writer) *Writer {
+	return &Writer{
+		w:    w,
+		obuf: make([]byte, obufLen),
+	}
+}
+
+// NewBufferedWriter returns a new Writer that compresses to w, using the
+// framing format described at
+// https://github.com/google/snappy/blob/master/framing_format.txt
+//
+// The Writer returned buffers writes. Users must call Close to guarantee all
+// data has been forwarded to the underlying io.Writer. They may also call
+// Flush zero or more times before calling Close.
+func NewBufferedWriter(w io.Writer) *Writer {
+	return &Writer{
+		w:    w,
+		ibuf: make([]byte, 0, maxBlockSize),
+		obuf: make([]byte, obufLen),
+	}
+}
+
+// Writer is an io.Writer that can write Snappy-compressed bytes.
+//
+// Writer handles the Snappy stream format, not the Snappy block format.
+type Writer struct {
+	w   io.Writer
+	err error
+
+	// ibuf is a buffer for the incoming (uncompressed) bytes.
+	//
+	// Its use is optional. For backwards compatibility, Writers created by the
+	// NewWriter function have ibuf == nil, do not buffer incoming bytes, and
+	// therefore do not need to be Flush'ed or Close'd.
+	ibuf []byte
+
+	// obuf is a buffer for the outgoing (compressed) bytes.
+	obuf []byte
+
+	// wroteStreamHeader is whether we have written the stream header.
+	wroteStreamHeader bool
+}
+
+// Reset discards the writer's state and switches the Snappy writer to write to
+// w. This permits reusing a Writer rather than allocating a new one.
+func (w *Writer) Reset(writer io.Writer) {
+	w.w = writer
+	w.err = nil
+	if w.ibuf != nil {
+		w.ibuf = w.ibuf[:0]
+	}
+	w.wroteStreamHeader = false
+}
+
+// Write satisfies the io.Writer interface.
+func (w *Writer) Write(p []byte) (nRet int, errRet error) {
+	if w.ibuf == nil {
+		// Do not buffer incoming bytes. This does not perform or compress well
+		// if the caller of Writer.Write writes many small slices. This
+		// behavior is therefore deprecated, but still supported for backwards
+		// compatibility with code that doesn't explicitly Flush or Close.
+		return w.write(p)
+	}
+
+	// The remainder of this method is based on bufio.Writer.Write from the
+	// standard library.
+
+	for len(p) > (cap(w.ibuf)-len(w.ibuf)) && w.err == nil {
+		var n int
+		if len(w.ibuf) == 0 {
+			// Large write, empty buffer.
+			// Write directly from p to avoid copy.
+			n, _ = w.write(p)
+		} else {
+			n = copy(w.ibuf[len(w.ibuf):cap(w.ibuf)], p)
+			w.ibuf = w.ibuf[:len(w.ibuf)+n]
+			w.Flush()
+		}
+		nRet += n
+		p = p[n:]
+	}
+	if w.err != nil {
+		return nRet, w.err
+	}
+	n := copy(w.ibuf[len(w.ibuf):cap(w.ibuf)], p)
+	w.ibuf = w.ibuf[:len(w.ibuf)+n]
+	nRet += n
+	return nRet, nil
+}
+
+func (w *Writer) write(p []byte) (nRet int, errRet error) {
+	if w.err != nil {
+		return 0, w.err
+	}
+	for len(p) > 0 {
+		obufStart := len(magicChunk)
+		if !w.wroteStreamHeader {
+			w.wroteStreamHeader = true
+			copy(w.obuf, magicChunk)
+			obufStart = 0
+		}
+
+		var uncompressed []byte
+		if len(p) > maxBlockSize {
+			uncompressed, p = p[:maxBlockSize], p[maxBlockSize:]
+		} else {
+			uncompressed, p = p, nil
+		}
+		checksum := crc(uncompressed)
+
+		// Compress the buffer, discarding the result if the improvement
+		// isn't at least 12.5%.
+		compressed := Encode(w.obuf[obufHeaderLen:], uncompressed)
+		chunkType := uint8(chunkTypeCompressedData)
+		chunkLen := 4 + len(compressed)
+		obufEnd := obufHeaderLen + len(compressed)
+		if len(compressed) >= len(uncompressed)-len(uncompressed)/8 {
+			chunkType = chunkTypeUncompressedData
+			chunkLen = 4 + len(uncompressed)
+			obufEnd = obufHeaderLen
+		}
+
+		// Fill in the per-chunk header that comes before the body.
+		w.obuf[len(magicChunk)+0] = chunkType
+		w.obuf[len(magicChunk)+1] = uint8(chunkLen >> 0)
+		w.obuf[len(magicChunk)+2] = uint8(chunkLen >> 8)
+		w.obuf[len(magicChunk)+3] = uint8(chunkLen >> 16)
+		w.obuf[len(magicChunk)+4] = uint8(checksum >> 0)
+		w.obuf[len(magicChunk)+5] = uint8(checksum >> 8)
+		w.obuf[len(magicChunk)+6] = uint8(checksum >> 16)
+		w.obuf[len(magicChunk)+7] = uint8(checksum >> 24)
+
+		if _, err := w.w.Write(w.obuf[obufStart:obufEnd]); err != nil {
+			w.err = err
+			return nRet, err
+		}
+		if chunkType == chunkTypeUncompressedData {
+			if _, err := w.w.Write(uncompressed); err != nil {
+				w.err = err
+				return nRet, err
+			}
+		}
+		nRet += len(uncompressed)
+	}
+	return nRet, nil
+}
+
+// Flush flushes the Writer to its underlying io.Writer.
+func (w *Writer) Flush() error {
+	if w.err != nil {
+		return w.err
+	}
+	if len(w.ibuf) == 0 {
+		return nil
+	}
+	w.write(w.ibuf)
+	w.ibuf = w.ibuf[:0]
+	return w.err
+}
+
+// Close calls Flush and then closes the Writer.
+func (w *Writer) Close() error {
+	w.Flush()
+	ret := w.err
+	if w.err == nil {
+		w.err = errClosed
+	}
+	return ret
+}

vendor/github.com/golang/snappy/encode_amd64.s

@@ -0,0 +1,730 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !appengine
+// +build gc
+// +build !noasm
+
+#include "textflag.h"
+
+// The XXX lines assemble on Go 1.4, 1.5 and 1.7, but not 1.6, due to a
+// Go toolchain regression. See https://github.com/golang/go/issues/15426 and
+// https://github.com/golang/snappy/issues/29
+//
+// As a workaround, the package was built with a known good assembler, and
+// those instructions were disassembled by "objdump -d" to yield the
+//	4e 0f b7 7c 5c 78       movzwq 0x78(%rsp,%r11,2),%r15
+// style comments, in AT&T asm syntax. Note that rsp here is a physical
+// register, not Go/asm's SP pseudo-register (see https://golang.org/doc/asm).
+// The instructions were then encoded as "BYTE $0x.." sequences, which assemble
+// fine on Go 1.6.
+
+// The asm code generally follows the pure Go code in encode_other.go, except
+// where marked with a "!!!".
+
+// ----------------------------------------------------------------------------
+
+// func emitLiteral(dst, lit []byte) int
+//
+// All local variables fit into registers. The register allocation:
+//	- AX	len(lit)
+//	- BX	n
+//	- DX	return value
+//	- DI	&dst[i]
+//	- R10	&lit[0]
+//
+// The 24 bytes of stack space is to call runtime·memmove.
+//
+// The unusual register allocation of local variables, such as R10 for the
+// source pointer, matches the allocation used at the call site in encodeBlock,
+// which makes it easier to manually inline this function.
+TEXT ·emitLiteral(SB), NOSPLIT, $24-56
+	MOVQ dst_base+0(FP), DI
+	MOVQ lit_base+24(FP), R10
+	MOVQ lit_len+32(FP), AX
+	MOVQ AX, DX
+	MOVL AX, BX
+	SUBL $1, BX
+
+	CMPL BX, $60
+	JLT  oneByte
+	CMPL BX, $256
+	JLT  twoBytes
+
+threeBytes:
+	MOVB $0xf4, 0(DI)
+	MOVW BX, 1(DI)
+	ADDQ $3, DI
+	ADDQ $3, DX
+	JMP  memmove
+
+twoBytes:
+	MOVB $0xf0, 0(DI)
+	MOVB BX, 1(DI)
+	ADDQ $2, DI
+	ADDQ $2, DX
+	JMP  memmove
+
+oneByte:
+	SHLB $2, BX
+	MOVB BX, 0(DI)
+	ADDQ $1, DI
+	ADDQ $1, DX
+
+memmove:
+	MOVQ DX, ret+48(FP)
+
+	// copy(dst[i:], lit)
+	//
+	// This means calling runtime·memmove(&dst[i], &lit[0], len(lit)), so we push
+	// DI, R10 and AX as arguments.
+	MOVQ DI, 0(SP)
+	MOVQ R10, 8(SP)
+	MOVQ AX, 16(SP)
+	CALL runtime·memmove(SB)
+	RET
+
+// ----------------------------------------------------------------------------
+
+// func emitCopy(dst []byte, offset, length int) int
+//
+// All local variables fit into registers. The register allocation:
+//	- AX	length
+//	- SI	&dst[0]
+//	- DI	&dst[i]
+//	- R11	offset
+//
+// The unusual register allocation of local variables, such as R11 for the
+// offset, matches the allocation used at the call site in encodeBlock, which
+// makes it easier to manually inline this function.
+TEXT ·emitCopy(SB), NOSPLIT, $0-48
+	MOVQ dst_base+0(FP), DI
+	MOVQ DI, SI
+	MOVQ offset+24(FP), R11
+	MOVQ length+32(FP), AX
+
+loop0:
+	// for length >= 68 { etc }
+	CMPL AX, $68
+	JLT  step1
+
+	// Emit a length 64 copy, encoded as 3 bytes.
+	MOVB $0xfe, 0(DI)
+	MOVW R11, 1(DI)
+	ADDQ $3, DI
+	SUBL $64, AX
+	JMP  loop0
+
+step1:
+	// if length > 64 { etc }
+	CMPL AX, $64
+	JLE  step2
+
+	// Emit a length 60 copy, encoded as 3 bytes.
+	MOVB $0xee, 0(DI)
+	MOVW R11, 1(DI)
+	ADDQ $3, DI
+	SUBL $60, AX
+
+step2:
+	// if length >= 12 || offset >= 2048 { goto step3 }
+	CMPL AX, $12
+	JGE  step3
+	CMPL R11, $2048
+	JGE  step3
+
+	// Emit the remaining copy, encoded as 2 bytes.
+	MOVB R11, 1(DI)
+	SHRL $8, R11
+	SHLB $5, R11
+	SUBB $4, AX
+	SHLB $2, AX
+	ORB  AX, R11
+	ORB  $1, R11
+	MOVB R11, 0(DI)
+	ADDQ $2, DI
+
+	// Return the number of bytes written.
+	SUBQ SI, DI
+	MOVQ DI, ret+40(FP)
+	RET
+
+step3:
+	// Emit the remaining copy, encoded as 3 bytes.
+	SUBL $1, AX
+	SHLB $2, AX
+	ORB  $2, AX
+	MOVB AX, 0(DI)
+	MOVW R11, 1(DI)
+	ADDQ $3, DI
+
+	// Return the number of bytes written.
+	SUBQ SI, DI
+	MOVQ DI, ret+40(FP)
+	RET
+
+// ----------------------------------------------------------------------------
+
+// func extendMatch(src []byte, i, j int) int
+//
+// All local variables fit into registers. The register allocation:
+//	- DX	&src[0]
+//	- SI	&src[j]
+//	- R13	&src[len(src) - 8]
+//	- R14	&src[len(src)]
+//	- R15	&src[i]
+//
+// The unusual register allocation of local variables, such as R15 for a source
+// pointer, matches the allocation used at the call site in encodeBlock, which
+// makes it easier to manually inline this function.
+TEXT ·extendMatch(SB), NOSPLIT, $0-48
+	MOVQ src_base+0(FP), DX
+	MOVQ src_len+8(FP), R14
+	MOVQ i+24(FP), R15
+	MOVQ j+32(FP), SI
+	ADDQ DX, R14
+	ADDQ DX, R15
+	ADDQ DX, SI
+	MOVQ R14, R13
+	SUBQ $8, R13
+
+cmp8:
+	// As long as we are 8 or more bytes before the end of src, we can load and
+	// compare 8 bytes at a time. If those 8 bytes are equal, repeat.
+	CMPQ SI, R13
+	JA   cmp1
+	MOVQ (R15), AX
+	MOVQ (SI), BX
+	CMPQ AX, BX
+	JNE  bsf
+	ADDQ $8, R15
+	ADDQ $8, SI
+	JMP  cmp8
+
+bsf:
+	// If those 8 bytes were not equal, XOR the two 8 byte values, and return
+	// the index of the first byte that differs. The BSF instruction finds the
+	// least significant 1 bit, the amd64 architecture is little-endian, and
+	// the shift by 3 converts a bit index to a byte index.
+	XORQ AX, BX
+	BSFQ BX, BX
+	SHRQ $3, BX
+	ADDQ BX, SI
+
+	// Convert from &src[ret] to ret.
+	SUBQ DX, SI
+	MOVQ SI, ret+40(FP)
+	RET
+
+cmp1:
+	// In src's tail, compare 1 byte at a time.
+	CMPQ SI, R14
+	JAE  extendMatchEnd
+	MOVB (R15), AX
+	MOVB (SI), BX
+	CMPB AX, BX
+	JNE  extendMatchEnd
+	ADDQ $1, R15
+	ADDQ $1, SI
+	JMP  cmp1
+
+extendMatchEnd:
+	// Convert from &src[ret] to ret.
+	SUBQ DX, SI
+	MOVQ SI, ret+40(FP)
+	RET
+
+// ----------------------------------------------------------------------------
+
+// func encodeBlock(dst, src []byte) (d int)
+//
+// All local variables fit into registers, other than "var table". The register
+// allocation:
+//	- AX	.	.
+//	- BX	.	.
+//	- CX	56	shift (note that amd64 shifts by non-immediates must use CX).
+//	- DX	64	&src[0], tableSize
+//	- SI	72	&src[s]
+//	- DI	80	&dst[d]
+//	- R9	88	sLimit
+//	- R10	.	&src[nextEmit]
+//	- R11	96	prevHash, currHash, nextHash, offset
+//	- R12	104	&src[base], skip
+//	- R13	.	&src[nextS], &src[len(src) - 8]
+//	- R14	.	len(src), bytesBetweenHashLookups, &src[len(src)], x
+//	- R15	112	candidate
+//
+// The second column (56, 64, etc) is the stack offset to spill the registers
+// when calling other functions. We could pack this slightly tighter, but it's
+// simpler to have a dedicated spill map independent of the function called.
+//
+// "var table [maxTableSize]uint16" takes up 32768 bytes of stack space. An
+// extra 56 bytes, to call other functions, and an extra 64 bytes, to spill
+// local variables (registers) during calls gives 32768 + 56 + 64 = 32888.
+TEXT ·encodeBlock(SB), 0, $32888-56
+	MOVQ dst_base+0(FP), DI
+	MOVQ src_base+24(FP), SI
+	MOVQ src_len+32(FP), R14
+
+	// shift, tableSize := uint32(32-8), 1<<8
+	MOVQ $24, CX
+	MOVQ $256, DX
+
+calcShift:
+	// for ; tableSize < maxTableSize && tableSize < len(src); tableSize *= 2 {
+	//	shift--
+	// }
+	CMPQ DX, $16384
+	JGE  varTable
+	CMPQ DX, R14
+	JGE  varTable
+	SUBQ $1, CX
+	SHLQ $1, DX
+	JMP  calcShift
+
+varTable:
+	// var table [maxTableSize]uint16
+	//
+	// In the asm code, unlike the Go code, we can zero-initialize only the
+	// first tableSize elements. Each uint16 element is 2 bytes and each MOVOU
+	// writes 16 bytes, so we can do only tableSize/8 writes instead of the
+	// 2048 writes that would zero-initialize all of table's 32768 bytes.
+	SHRQ $3, DX
+	LEAQ table-32768(SP), BX
+	PXOR X0, X0
+
+memclr:
+	MOVOU X0, 0(BX)
+	ADDQ  $16, BX
+	SUBQ  $1, DX
+	JNZ   memclr
+
+	// !!! DX = &src[0]
+	MOVQ SI, DX
+
+	// sLimit := len(src) - inputMargin
+	MOVQ R14, R9
+	SUBQ $15, R9
+
+	// !!! Pre-emptively spill CX, DX and R9 to the stack. Their values don't
+	// change for the rest of the function.
+	MOVQ CX, 56(SP)
+	MOVQ DX, 64(SP)
+	MOVQ R9, 88(SP)
+
+	// nextEmit := 0
+	MOVQ DX, R10
+
+	// s := 1
+	ADDQ $1, SI
+
+	// nextHash := hash(load32(src, s), shift)
+	MOVL  0(SI), R11
+	IMULL $0x1e35a7bd, R11
+	SHRL  CX, R11
+
+outer:
+	// for { etc }
+
+	// skip := 32
+	MOVQ $32, R12
+
+	// nextS := s
+	MOVQ SI, R13
+
+	// candidate := 0
+	MOVQ $0, R15
+
+inner0:
+	// for { etc }
+
+	// s := nextS
+	MOVQ R13, SI
+
+	// bytesBetweenHashLookups := skip >> 5
+	MOVQ R12, R14
+	SHRQ $5, R14
+
+	// nextS = s + bytesBetweenHashLookups
+	ADDQ R14, R13
+
+	// skip += bytesBetweenHashLookups
+	ADDQ R14, R12
+
+	// if nextS > sLimit { goto emitRemainder }
+	MOVQ R13, AX
+	SUBQ DX, AX
+	CMPQ AX, R9
+	JA   emitRemainder
+
+	// candidate = int(table[nextHash])
+	// XXX: MOVWQZX table-32768(SP)(R11*2), R15
+	// XXX: 4e 0f b7 7c 5c 78       movzwq 0x78(%rsp,%r11,2),%r15
+	BYTE $0x4e
+	BYTE $0x0f
+	BYTE $0xb7
+	BYTE $0x7c
+	BYTE $0x5c
+	BYTE $0x78
+
+	// table[nextHash] = uint16(s)
+	MOVQ SI, AX
+	SUBQ DX, AX
+
+	// XXX: MOVW AX, table-32768(SP)(R11*2)
+	// XXX: 66 42 89 44 5c 78       mov    %ax,0x78(%rsp,%r11,2)
+	BYTE $0x66
+	BYTE $0x42
+	BYTE $0x89
+	BYTE $0x44
+	BYTE $0x5c
+	BYTE $0x78
+
+	// nextHash = hash(load32(src, nextS), shift)
+	MOVL  0(R13), R11
+	IMULL $0x1e35a7bd, R11
+	SHRL  CX, R11
+
+	// if load32(src, s) != load32(src, candidate) { continue } break
+	MOVL 0(SI), AX
+	MOVL (DX)(R15*1), BX
+	CMPL AX, BX
+	JNE  inner0
+
+fourByteMatch:
+	// As per the encode_other.go code:
+	//
+	// A 4-byte match has been found. We'll later see etc.
+
+	// !!! Jump to a fast path for short (<= 16 byte) literals. See the comment
+	// on inputMargin in encode.go.
+	MOVQ SI, AX
+	SUBQ R10, AX
+	CMPQ AX, $16
+	JLE  emitLiteralFastPath
+
+	// ----------------------------------------
+	// Begin inline of the emitLiteral call.
+	//
+	// d += emitLiteral(dst[d:], src[nextEmit:s])
+
+	MOVL AX, BX
+	SUBL $1, BX
+
+	CMPL BX, $60
+	JLT  inlineEmitLiteralOneByte
+	CMPL BX, $256
+	JLT  inlineEmitLiteralTwoBytes
+
+inlineEmitLiteralThreeBytes:
+	MOVB $0xf4, 0(DI)
+	MOVW BX, 1(DI)
+	ADDQ $3, DI
+	JMP  inlineEmitLiteralMemmove
+
+inlineEmitLiteralTwoBytes:
+	MOVB $0xf0, 0(DI)
+	MOVB BX, 1(DI)
+	ADDQ $2, DI
+	JMP  inlineEmitLiteralMemmove
+
+inlineEmitLiteralOneByte:
+	SHLB $2, BX
+	MOVB BX, 0(DI)
+	ADDQ $1, DI
+
+inlineEmitLiteralMemmove:
+	// Spill local variables (registers) onto the stack; call; unspill.
+	//
+	// copy(dst[i:], lit)
+	//
+	// This means calling runtime·memmove(&dst[i], &lit[0], len(lit)), so we push
+	// DI, R10 and AX as arguments.
+	MOVQ DI, 0(SP)
+	MOVQ R10, 8(SP)
+	MOVQ AX, 16(SP)
+	ADDQ AX, DI              // Finish the "d +=" part of "d += emitLiteral(etc)".
+	MOVQ SI, 72(SP)
+	MOVQ DI, 80(SP)
+	MOVQ R15, 112(SP)
+	CALL runtime·memmove(SB)
+	MOVQ 56(SP), CX
+	MOVQ 64(SP), DX
+	MOVQ 72(SP), SI
+	MOVQ 80(SP), DI
+	MOVQ 88(SP), R9
+	MOVQ 112(SP), R15
+	JMP  inner1
+
+inlineEmitLiteralEnd:
+	// End inline of the emitLiteral call.
+	// ----------------------------------------
+
+emitLiteralFastPath:
+	// !!! Emit the 1-byte encoding "uint8(len(lit)-1)<<2".
+	MOVB AX, BX
+	SUBB $1, BX
+	SHLB $2, BX
+	MOVB BX, (DI)
+	ADDQ $1, DI
+
+	// !!! Implement the copy from lit to dst as a 16-byte load and store.
+	// (Encode's documentation says that dst and src must not overlap.)
+	//
+	// This always copies 16 bytes, instead of only len(lit) bytes, but that's
+	// OK. Subsequent iterations will fix up the overrun.
+	//
+	// Note that on amd64, it is legal and cheap to issue unaligned 8-byte or
+	// 16-byte loads and stores. This technique probably wouldn't be as
+	// effective on architectures that are fussier about alignment.
+	MOVOU 0(R10), X0
+	MOVOU X0, 0(DI)
+	ADDQ  AX, DI
+
+inner1:
+	// for { etc }
+
+	// base := s
+	MOVQ SI, R12
+
+	// !!! offset := base - candidate
+	MOVQ R12, R11
+	SUBQ R15, R11
+	SUBQ DX, R11
+
+	// ----------------------------------------
+	// Begin inline of the extendMatch call.
+	//
+	// s = extendMatch(src, candidate+4, s+4)
+
+	// !!! R14 = &src[len(src)]
+	MOVQ src_len+32(FP), R14
+	ADDQ DX, R14
+
+	// !!! R13 = &src[len(src) - 8]
+	MOVQ R14, R13
+	SUBQ $8, R13
+
+	// !!! R15 = &src[candidate + 4]
+	ADDQ $4, R15
+	ADDQ DX, R15
+
+	// !!! s += 4
+	ADDQ $4, SI
+
+inlineExtendMatchCmp8:
+	// As long as we are 8 or more bytes before the end of src, we can load and
+	// compare 8 bytes at a time. If those 8 bytes are equal, repeat.
+	CMPQ SI, R13
+	JA   inlineExtendMatchCmp1
+	MOVQ (R15), AX
+	MOVQ (SI), BX
+	CMPQ AX, BX
+	JNE  inlineExtendMatchBSF
+	ADDQ $8, R15
+	ADDQ $8, SI
+	JMP  inlineExtendMatchCmp8
+
+inlineExtendMatchBSF:
+	// If those 8 bytes were not equal, XOR the two 8 byte values, and return
+	// the index of the first byte that differs. The BSF instruction finds the
+	// least significant 1 bit, the amd64 architecture is little-endian, and
+	// the shift by 3 converts a bit index to a byte index.
+	XORQ AX, BX
+	BSFQ BX, BX
+	SHRQ $3, BX
+	ADDQ BX, SI
+	JMP  inlineExtendMatchEnd
+
+inlineExtendMatchCmp1:
+	// In src's tail, compare 1 byte at a time.
+	CMPQ SI, R14
+	JAE  inlineExtendMatchEnd
+	MOVB (R15), AX
+	MOVB (SI), BX
+	CMPB AX, BX
+	JNE  inlineExtendMatchEnd
+	ADDQ $1, R15
+	ADDQ $1, SI
+	JMP  inlineExtendMatchCmp1
+
+inlineExtendMatchEnd:
+	// End inline of the extendMatch call.
+	// ----------------------------------------
+
+	// ----------------------------------------
+	// Begin inline of the emitCopy call.
+	//
+	// d += emitCopy(dst[d:], base-candidate, s-base)
+
+	// !!! length := s - base
+	MOVQ SI, AX
+	SUBQ R12, AX
+
+inlineEmitCopyLoop0:
+	// for length >= 68 { etc }
+	CMPL AX, $68
+	JLT  inlineEmitCopyStep1
+
+	// Emit a length 64 copy, encoded as 3 bytes.
+	MOVB $0xfe, 0(DI)
+	MOVW R11, 1(DI)
+	ADDQ $3, DI
+	SUBL $64, AX
+	JMP  inlineEmitCopyLoop0
+
+inlineEmitCopyStep1:
+	// if length > 64 { etc }
+	CMPL AX, $64
+	JLE  inlineEmitCopyStep2
+
+	// Emit a length 60 copy, encoded as 3 bytes.
+	MOVB $0xee, 0(DI)
+	MOVW R11, 1(DI)
+	ADDQ $3, DI
+	SUBL $60, AX
+
+inlineEmitCopyStep2:
+	// if length >= 12 || offset >= 2048 { goto inlineEmitCopyStep3 }
+	CMPL AX, $12
+	JGE  inlineEmitCopyStep3
+	CMPL R11, $2048
+	JGE  inlineEmitCopyStep3
+
+	// Emit the remaining copy, encoded as 2 bytes.
+	MOVB R11, 1(DI)
+	SHRL $8, R11
+	SHLB $5, R11
+	SUBB $4, AX
+	SHLB $2, AX
+	ORB  AX, R11
+	ORB  $1, R11
+	MOVB R11, 0(DI)
+	ADDQ $2, DI
+	JMP  inlineEmitCopyEnd
+
+inlineEmitCopyStep3:
+	// Emit the remaining copy, encoded as 3 bytes.
+	SUBL $1, AX
+	SHLB $2, AX
+	ORB  $2, AX
+	MOVB AX, 0(DI)
+	MOVW R11, 1(DI)
+	ADDQ $3, DI
+
+inlineEmitCopyEnd:
+	// End inline of the emitCopy call.
+	// ----------------------------------------
+
+	// nextEmit = s
+	MOVQ SI, R10
+
+	// if s >= sLimit { goto emitRemainder }
+	MOVQ SI, AX
+	SUBQ DX, AX
+	CMPQ AX, R9
+	JAE  emitRemainder
+
+	// As per the encode_other.go code:
+	//
+	// We could immediately etc.
+
+	// x := load64(src, s-1)
+	MOVQ -1(SI), R14
+
+	// prevHash := hash(uint32(x>>0), shift)
+	MOVL  R14, R11
+	IMULL $0x1e35a7bd, R11
+	SHRL  CX, R11
+
+	// table[prevHash] = uint16(s-1)
+	MOVQ SI, AX
+	SUBQ DX, AX
+	SUBQ $1, AX
+
+	// XXX: MOVW AX, table-32768(SP)(R11*2)
+	// XXX: 66 42 89 44 5c 78       mov    %ax,0x78(%rsp,%r11,2)
+	BYTE $0x66
+	BYTE $0x42
+	BYTE $0x89
+	BYTE $0x44
+	BYTE $0x5c
+	BYTE $0x78
+
+	// currHash := hash(uint32(x>>8), shift)
+	SHRQ  $8, R14
+	MOVL  R14, R11
+	IMULL $0x1e35a7bd, R11
+	SHRL  CX, R11
+
+	// candidate = int(table[currHash])
+	// XXX: MOVWQZX table-32768(SP)(R11*2), R15
+	// XXX: 4e 0f b7 7c 5c 78       movzwq 0x78(%rsp,%r11,2),%r15
+	BYTE $0x4e
+	BYTE $0x0f
+	BYTE $0xb7
+	BYTE $0x7c
+	BYTE $0x5c
+	BYTE $0x78
+
+	// table[currHash] = uint16(s)
+	ADDQ $1, AX
+
+	// XXX: MOVW AX, table-32768(SP)(R11*2)
+	// XXX: 66 42 89 44 5c 78       mov    %ax,0x78(%rsp,%r11,2)
+	BYTE $0x66
+	BYTE $0x42
+	BYTE $0x89
+	BYTE $0x44
+	BYTE $0x5c
+	BYTE $0x78
+
+	// if uint32(x>>8) == load32(src, candidate) { continue }
+	MOVL (DX)(R15*1), BX
+	CMPL R14, BX
+	JEQ  inner1
+
+	// nextHash = hash(uint32(x>>16), shift)
+	SHRQ  $8, R14
+	MOVL  R14, R11
+	IMULL $0x1e35a7bd, R11
+	SHRL  CX, R11
+
+	// s++
+	ADDQ $1, SI
+
+	// break out of the inner1 for loop, i.e. continue the outer loop.
+	JMP outer
+
+emitRemainder:
+	// if nextEmit < len(src) { etc }
+	MOVQ src_len+32(FP), AX
+	ADDQ DX, AX
+	CMPQ R10, AX
+	JEQ  encodeBlockEnd
+
+	// d += emitLiteral(dst[d:], src[nextEmit:])
+	//
+	// Push args.
+	MOVQ DI, 0(SP)
+	MOVQ $0, 8(SP)   // Unnecessary, as the callee ignores it, but conservative.
+	MOVQ $0, 16(SP)  // Unnecessary, as the callee ignores it, but conservative.
+	MOVQ R10, 24(SP)
+	SUBQ R10, AX
+	MOVQ AX, 32(SP)
+	MOVQ AX, 40(SP)  // Unnecessary, as the callee ignores it, but conservative.
+
+	// Spill local variables (registers) onto the stack; call; unspill.
+	MOVQ DI, 80(SP)
+	CALL ·emitLiteral(SB)
+	MOVQ 80(SP), DI
+
+	// Finish the "d +=" part of "d += emitLiteral(etc)".
+	ADDQ 48(SP), DI
+
+encodeBlockEnd:
+	MOVQ dst_base+0(FP), AX
+	SUBQ AX, DI
+	MOVQ DI, d+48(FP)
+	RET

vendor/github.com/golang/snappy/encode_arm64.s

@@ -0,0 +1,722 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !appengine
+// +build gc
+// +build !noasm
+
+#include "textflag.h"
+
+// The asm code generally follows the pure Go code in encode_other.go, except
+// where marked with a "!!!".
+
+// ----------------------------------------------------------------------------
+
+// func emitLiteral(dst, lit []byte) int
+//
+// All local variables fit into registers. The register allocation:
+//	- R3	len(lit)
+//	- R4	n
+//	- R6	return value
+//	- R8	&dst[i]
+//	- R10	&lit[0]
+//
+// The 32 bytes of stack space is to call runtime·memmove.
+//
+// The unusual register allocation of local variables, such as R10 for the
+// source pointer, matches the allocation used at the call site in encodeBlock,
+// which makes it easier to manually inline this function.
+TEXT ·emitLiteral(SB), NOSPLIT, $32-56
+	MOVD dst_base+0(FP), R8
+	MOVD lit_base+24(FP), R10
+	MOVD lit_len+32(FP), R3
+	MOVD R3, R6
+	MOVW R3, R4
+	SUBW $1, R4, R4
+
+	CMPW $60, R4
+	BLT  oneByte
+	CMPW $256, R4
+	BLT  twoBytes
+
+threeBytes:
+	MOVD $0xf4, R2
+	MOVB R2, 0(R8)
+	MOVW R4, 1(R8)
+	ADD  $3, R8, R8
+	ADD  $3, R6, R6
+	B    memmove
+
+twoBytes:
+	MOVD $0xf0, R2
+	MOVB R2, 0(R8)
+	MOVB R4, 1(R8)
+	ADD  $2, R8, R8
+	ADD  $2, R6, R6
+	B    memmove
+
+oneByte:
+	LSLW $2, R4, R4
+	MOVB R4, 0(R8)
+	ADD  $1, R8, R8
+	ADD  $1, R6, R6
+
+memmove:
+	MOVD R6, ret+48(FP)
+
+	// copy(dst[i:], lit)
+	//
+	// This means calling runtime·memmove(&dst[i], &lit[0], len(lit)), so we push
+	// R8, R10 and R3 as arguments.
+	MOVD R8, 8(RSP)
+	MOVD R10, 16(RSP)
+	MOVD R3, 24(RSP)
+	CALL runtime·memmove(SB)
+	RET
+
+// ----------------------------------------------------------------------------
+
+// func emitCopy(dst []byte, offset, length int) int
+//
+// All local variables fit into registers. The register allocation:
+//	- R3	length
+//	- R7	&dst[0]
+//	- R8	&dst[i]
+//	- R11	offset
+//
+// The unusual register allocation of local variables, such as R11 for the
+// offset, matches the allocation used at the call site in encodeBlock, which
+// makes it easier to manually inline this function.
+TEXT ·emitCopy(SB), NOSPLIT, $0-48
+	MOVD dst_base+0(FP), R8
+	MOVD R8, R7
+	MOVD offset+24(FP), R11
+	MOVD length+32(FP), R3
+
+loop0:
+	// for length >= 68 { etc }
+	CMPW $68, R3
+	BLT  step1
+
+	// Emit a length 64 copy, encoded as 3 bytes.
+	MOVD $0xfe, R2
+	MOVB R2, 0(R8)
+	MOVW R11, 1(R8)
+	ADD  $3, R8, R8
+	SUB  $64, R3, R3
+	B    loop0
+
+step1:
+	// if length > 64 { etc }
+	CMP $64, R3
+	BLE step2
+
+	// Emit a length 60 copy, encoded as 3 bytes.
+	MOVD $0xee, R2
+	MOVB R2, 0(R8)
+	MOVW R11, 1(R8)
+	ADD  $3, R8, R8
+	SUB  $60, R3, R3
+
+step2:
+	// if length >= 12 || offset >= 2048 { goto step3 }
+	CMP  $12, R3
+	BGE  step3
+	CMPW $2048, R11
+	BGE  step3
+
+	// Emit the remaining copy, encoded as 2 bytes.
+	MOVB R11, 1(R8)
+	LSRW $3, R11, R11
+	AND  $0xe0, R11, R11
+	SUB  $4, R3, R3
+	LSLW $2, R3
+	AND  $0xff, R3, R3
+	ORRW R3, R11, R11
+	ORRW $1, R11, R11
+	MOVB R11, 0(R8)
+	ADD  $2, R8, R8
+
+	// Return the number of bytes written.
+	SUB  R7, R8, R8
+	MOVD R8, ret+40(FP)
+	RET
+
+step3:
+	// Emit the remaining copy, encoded as 3 bytes.
+	SUB  $1, R3, R3
+	AND  $0xff, R3, R3
+	LSLW $2, R3, R3
+	ORRW $2, R3, R3
+	MOVB R3, 0(R8)
+	MOVW R11, 1(R8)
+	ADD  $3, R8, R8
+
+	// Return the number of bytes written.
+	SUB  R7, R8, R8
+	MOVD R8, ret+40(FP)
+	RET
+
+// ----------------------------------------------------------------------------
+
+// func extendMatch(src []byte, i, j int) int
+//
+// All local variables fit into registers. The register allocation:
+//	- R6	&src[0]
+//	- R7	&src[j]
+//	- R13	&src[len(src) - 8]
+//	- R14	&src[len(src)]
+//	- R15	&src[i]
+//
+// The unusual register allocation of local variables, such as R15 for a source
+// pointer, matches the allocation used at the call site in encodeBlock, which
+// makes it easier to manually inline this function.
+TEXT ·extendMatch(SB), NOSPLIT, $0-48
+	MOVD src_base+0(FP), R6
+	MOVD src_len+8(FP), R14
+	MOVD i+24(FP), R15
+	MOVD j+32(FP), R7
+	ADD  R6, R14, R14
+	ADD  R6, R15, R15
+	ADD  R6, R7, R7
+	MOVD R14, R13
+	SUB  $8, R13, R13
+
+cmp8:
+	// As long as we are 8 or more bytes before the end of src, we can load and
+	// compare 8 bytes at a time. If those 8 bytes are equal, repeat.
+	CMP  R13, R7
+	BHI  cmp1
+	MOVD (R15), R3
+	MOVD (R7), R4
+	CMP  R4, R3
+	BNE  bsf
+	ADD  $8, R15, R15
+	ADD  $8, R7, R7
+	B    cmp8
+
+bsf:
+	// If those 8 bytes were not equal, XOR the two 8 byte values, and return
+	// the index of the first byte that differs.
+	// RBIT reverses the bit order, then CLZ counts the leading zeros, the
+	// combination of which finds the least significant bit which is set.
+	// The arm64 architecture is little-endian, and the shift by 3 converts
+	// a bit index to a byte index.
+	EOR  R3, R4, R4
+	RBIT R4, R4
+	CLZ  R4, R4
+	ADD  R4>>3, R7, R7
+
+	// Convert from &src[ret] to ret.
+	SUB  R6, R7, R7
+	MOVD R7, ret+40(FP)
+	RET
+
+cmp1:
+	// In src's tail, compare 1 byte at a time.
+	CMP  R7, R14
+	BLS  extendMatchEnd
+	MOVB (R15), R3
+	MOVB (R7), R4
+	CMP  R4, R3
+	BNE  extendMatchEnd
+	ADD  $1, R15, R15
+	ADD  $1, R7, R7
+	B    cmp1
+
+extendMatchEnd:
+	// Convert from &src[ret] to ret.
+	SUB  R6, R7, R7
+	MOVD R7, ret+40(FP)
+	RET
+
+// ----------------------------------------------------------------------------
+
+// func encodeBlock(dst, src []byte) (d int)
+//
+// All local variables fit into registers, other than "var table". The register
+// allocation:
+//	- R3	.	.
+//	- R4	.	.
+//	- R5	64	shift
+//	- R6	72	&src[0], tableSize
+//	- R7	80	&src[s]
+//	- R8	88	&dst[d]
+//	- R9	96	sLimit
+//	- R10	.	&src[nextEmit]
+//	- R11	104	prevHash, currHash, nextHash, offset
+//	- R12	112	&src[base], skip
+//	- R13	.	&src[nextS], &src[len(src) - 8]
+//	- R14	.	len(src), bytesBetweenHashLookups, &src[len(src)], x
+//	- R15	120	candidate
+//	- R16	.	hash constant, 0x1e35a7bd
+//	- R17	.	&table
+//	- .  	128	table
+//
+// The second column (64, 72, etc) is the stack offset to spill the registers
+// when calling other functions. We could pack this slightly tighter, but it's
+// simpler to have a dedicated spill map independent of the function called.
+//
+// "var table [maxTableSize]uint16" takes up 32768 bytes of stack space. An
+// extra 64 bytes, to call other functions, and an extra 64 bytes, to spill
+// local variables (registers) during calls gives 32768 + 64 + 64 = 32896.
+TEXT ·encodeBlock(SB), 0, $32896-56
+	MOVD dst_base+0(FP), R8
+	MOVD src_base+24(FP), R7
+	MOVD src_len+32(FP), R14
+
+	// shift, tableSize := uint32(32-8), 1<<8
+	MOVD  $24, R5
+	MOVD  $256, R6
+	MOVW  $0xa7bd, R16
+	MOVKW $(0x1e35<<16), R16
+
+calcShift:
+	// for ; tableSize < maxTableSize && tableSize < len(src); tableSize *= 2 {
+	//	shift--
+	// }
+	MOVD $16384, R2
+	CMP  R2, R6
+	BGE  varTable
+	CMP  R14, R6
+	BGE  varTable
+	SUB  $1, R5, R5
+	LSL  $1, R6, R6
+	B    calcShift
+
+varTable:
+	// var table [maxTableSize]uint16
+	//
+	// In the asm code, unlike the Go code, we can zero-initialize only the
+	// first tableSize elements. Each uint16 element is 2 bytes and each
+	// iterations writes 64 bytes, so we can do only tableSize/32 writes
+	// instead of the 2048 writes that would zero-initialize all of table's
+	// 32768 bytes. This clear could overrun the first tableSize elements, but
+	// it won't overrun the allocated stack size.
+	ADD  $128, RSP, R17
+	MOVD R17, R4
+
+	// !!! R6 = &src[tableSize]
+	ADD R6<<1, R17, R6
+
+memclr:
+	STP.P (ZR, ZR), 64(R4)
+	STP   (ZR, ZR), -48(R4)
+	STP   (ZR, ZR), -32(R4)
+	STP   (ZR, ZR), -16(R4)
+	CMP   R4, R6
+	BHI   memclr
+
+	// !!! R6 = &src[0]
+	MOVD R7, R6
+
+	// sLimit := len(src) - inputMargin
+	MOVD R14, R9
+	SUB  $15, R9, R9
+
+	// !!! Pre-emptively spill R5, R6 and R9 to the stack. Their values don't
+	// change for the rest of the function.
+	MOVD R5, 64(RSP)
+	MOVD R6, 72(RSP)
+	MOVD R9, 96(RSP)
+
+	// nextEmit := 0
+	MOVD R6, R10
+
+	// s := 1
+	ADD $1, R7, R7
+
+	// nextHash := hash(load32(src, s), shift)
+	MOVW 0(R7), R11
+	MULW R16, R11, R11
+	LSRW R5, R11, R11
+
+outer:
+	// for { etc }
+
+	// skip := 32
+	MOVD $32, R12
+
+	// nextS := s
+	MOVD R7, R13
+
+	// candidate := 0
+	MOVD $0, R15
+
+inner0:
+	// for { etc }
+
+	// s := nextS
+	MOVD R13, R7
+
+	// bytesBetweenHashLookups := skip >> 5
+	MOVD R12, R14
+	LSR  $5, R14, R14
+
+	// nextS = s + bytesBetweenHashLookups
+	ADD R14, R13, R13
+
+	// skip += bytesBetweenHashLookups
+	ADD R14, R12, R12
+
+	// if nextS > sLimit { goto emitRemainder }
+	MOVD R13, R3
+	SUB  R6, R3, R3
+	CMP  R9, R3
+	BHI  emitRemainder
+
+	// candidate = int(table[nextHash])
+	MOVHU 0(R17)(R11<<1), R15
+
+	// table[nextHash] = uint16(s)
+	MOVD R7, R3
+	SUB  R6, R3, R3
+
+	MOVH R3, 0(R17)(R11<<1)
+
+	// nextHash = hash(load32(src, nextS), shift)
+	MOVW 0(R13), R11
+	MULW R16, R11
+	LSRW R5, R11, R11
+
+	// if load32(src, s) != load32(src, candidate) { continue } break
+	MOVW 0(R7), R3
+	MOVW (R6)(R15), R4
+	CMPW R4, R3
+	BNE  inner0
+
+fourByteMatch:
+	// As per the encode_other.go code:
+	//
+	// A 4-byte match has been found. We'll later see etc.
+
+	// !!! Jump to a fast path for short (<= 16 byte) literals. See the comment
+	// on inputMargin in encode.go.
+	MOVD R7, R3
+	SUB  R10, R3, R3
+	CMP  $16, R3
+	BLE  emitLiteralFastPath
+
+	// ----------------------------------------
+	// Begin inline of the emitLiteral call.
+	//
+	// d += emitLiteral(dst[d:], src[nextEmit:s])
+
+	MOVW R3, R4
+	SUBW $1, R4, R4
+
+	MOVW $60, R2
+	CMPW R2, R4
+	BLT  inlineEmitLiteralOneByte
+	MOVW $256, R2
+	CMPW R2, R4
+	BLT  inlineEmitLiteralTwoBytes
+
+inlineEmitLiteralThreeBytes:
+	MOVD $0xf4, R1
+	MOVB R1, 0(R8)
+	MOVW R4, 1(R8)
+	ADD  $3, R8, R8
+	B    inlineEmitLiteralMemmove
+
+inlineEmitLiteralTwoBytes:
+	MOVD $0xf0, R1
+	MOVB R1, 0(R8)
+	MOVB R4, 1(R8)
+	ADD  $2, R8, R8
+	B    inlineEmitLiteralMemmove
+
+inlineEmitLiteralOneByte:
+	LSLW $2, R4, R4
+	MOVB R4, 0(R8)
+	ADD  $1, R8, R8
+
+inlineEmitLiteralMemmove:
+	// Spill local variables (registers) onto the stack; call; unspill.
+	//
+	// copy(dst[i:], lit)
+	//
+	// This means calling runtime·memmove(&dst[i], &lit[0], len(lit)), so we push
+	// R8, R10 and R3 as arguments.
+	MOVD R8, 8(RSP)
+	MOVD R10, 16(RSP)
+	MOVD R3, 24(RSP)
+
+	// Finish the "d +=" part of "d += emitLiteral(etc)".
+	ADD   R3, R8, R8
+	MOVD  R7, 80(RSP)
+	MOVD  R8, 88(RSP)
+	MOVD  R15, 120(RSP)
+	CALL  runtime·memmove(SB)
+	MOVD  64(RSP), R5
+	MOVD  72(RSP), R6
+	MOVD  80(RSP), R7
+	MOVD  88(RSP), R8
+	MOVD  96(RSP), R9
+	MOVD  120(RSP), R15
+	ADD   $128, RSP, R17
+	MOVW  $0xa7bd, R16
+	MOVKW $(0x1e35<<16), R16
+	B     inner1
+
+inlineEmitLiteralEnd:
+	// End inline of the emitLiteral call.
+	// ----------------------------------------
+
+emitLiteralFastPath:
+	// !!! Emit the 1-byte encoding "uint8(len(lit)-1)<<2".
+	MOVB R3, R4
+	SUBW $1, R4, R4
+	AND  $0xff, R4, R4
+	LSLW $2, R4, R4
+	MOVB R4, (R8)
+	ADD  $1, R8, R8
+
+	// !!! Implement the copy from lit to dst as a 16-byte load and store.
+	// (Encode's documentation says that dst and src must not overlap.)
+	//
+	// This always copies 16 bytes, instead of only len(lit) bytes, but that's
+	// OK. Subsequent iterations will fix up the overrun.
+	//
+	// Note that on arm64, it is legal and cheap to issue unaligned 8-byte or
+	// 16-byte loads and stores. This technique probably wouldn't be as
+	// effective on architectures that are fussier about alignment.
+	LDP 0(R10), (R0, R1)
+	STP (R0, R1), 0(R8)
+	ADD R3, R8, R8
+
+inner1:
+	// for { etc }
+
+	// base := s
+	MOVD R7, R12
+
+	// !!! offset := base - candidate
+	MOVD R12, R11
+	SUB  R15, R11, R11
+	SUB  R6, R11, R11
+
+	// ----------------------------------------
+	// Begin inline of the extendMatch call.
+	//
+	// s = extendMatch(src, candidate+4, s+4)
+
+	// !!! R14 = &src[len(src)]
+	MOVD src_len+32(FP), R14
+	ADD  R6, R14, R14
+
+	// !!! R13 = &src[len(src) - 8]
+	MOVD R14, R13
+	SUB  $8, R13, R13
+
+	// !!! R15 = &src[candidate + 4]
+	ADD $4, R15, R15
+	ADD R6, R15, R15
+
+	// !!! s += 4
+	ADD $4, R7, R7
+
+inlineExtendMatchCmp8:
+	// As long as we are 8 or more bytes before the end of src, we can load and
+	// compare 8 bytes at a time. If those 8 bytes are equal, repeat.
+	CMP  R13, R7
+	BHI  inlineExtendMatchCmp1
+	MOVD (R15), R3
+	MOVD (R7), R4
+	CMP  R4, R3
+	BNE  inlineExtendMatchBSF
+	ADD  $8, R15, R15
+	ADD  $8, R7, R7
+	B    inlineExtendMatchCmp8
+
+inlineExtendMatchBSF:
+	// If those 8 bytes were not equal, XOR the two 8 byte values, and return
+	// the index of the first byte that differs.
+	// RBIT reverses the bit order, then CLZ counts the leading zeros, the
+	// combination of which finds the least significant bit which is set.
+	// The arm64 architecture is little-endian, and the shift by 3 converts
+	// a bit index to a byte index.
+	EOR  R3, R4, R4
+	RBIT R4, R4
+	CLZ  R4, R4
+	ADD  R4>>3, R7, R7
+	B    inlineExtendMatchEnd
+
+inlineExtendMatchCmp1:
+	// In src's tail, compare 1 byte at a time.
+	CMP  R7, R14
+	BLS  inlineExtendMatchEnd
+	MOVB (R15), R3
+	MOVB (R7), R4
+	CMP  R4, R3
+	BNE  inlineExtendMatchEnd
+	ADD  $1, R15, R15
+	ADD  $1, R7, R7
+	B    inlineExtendMatchCmp1
+
+inlineExtendMatchEnd:
+	// End inline of the extendMatch call.
+	// ----------------------------------------
+
+	// ----------------------------------------
+	// Begin inline of the emitCopy call.
+	//
+	// d += emitCopy(dst[d:], base-candidate, s-base)
+
+	// !!! length := s - base
+	MOVD R7, R3
+	SUB  R12, R3, R3
+
+inlineEmitCopyLoop0:
+	// for length >= 68 { etc }
+	MOVW $68, R2
+	CMPW R2, R3
+	BLT  inlineEmitCopyStep1
+
+	// Emit a length 64 copy, encoded as 3 bytes.
+	MOVD $0xfe, R1
+	MOVB R1, 0(R8)
+	MOVW R11, 1(R8)
+	ADD  $3, R8, R8
+	SUBW $64, R3, R3
+	B    inlineEmitCopyLoop0
+
+inlineEmitCopyStep1:
+	// if length > 64 { etc }
+	MOVW $64, R2
+	CMPW R2, R3
+	BLE  inlineEmitCopyStep2
+
+	// Emit a length 60 copy, encoded as 3 bytes.
+	MOVD $0xee, R1
+	MOVB R1, 0(R8)
+	MOVW R11, 1(R8)
+	ADD  $3, R8, R8
+	SUBW $60, R3, R3
+
+inlineEmitCopyStep2:
+	// if length >= 12 || offset >= 2048 { goto inlineEmitCopyStep3 }
+	MOVW $12, R2
+	CMPW R2, R3
+	BGE  inlineEmitCopyStep3
+	MOVW $2048, R2
+	CMPW R2, R11
+	BGE  inlineEmitCopyStep3
+
+	// Emit the remaining copy, encoded as 2 bytes.
+	MOVB R11, 1(R8)
+	LSRW $8, R11, R11
+	LSLW $5, R11, R11
+	SUBW $4, R3, R3
+	AND  $0xff, R3, R3
+	LSLW $2, R3, R3
+	ORRW R3, R11, R11
+	ORRW $1, R11, R11
+	MOVB R11, 0(R8)
+	ADD  $2, R8, R8
+	B    inlineEmitCopyEnd
+
+inlineEmitCopyStep3:
+	// Emit the remaining copy, encoded as 3 bytes.
+	SUBW $1, R3, R3
+	LSLW $2, R3, R3
+	ORRW $2, R3, R3
+	MOVB R3, 0(R8)
+	MOVW R11, 1(R8)
+	ADD  $3, R8, R8
+
+inlineEmitCopyEnd:
+	// End inline of the emitCopy call.
+	// ----------------------------------------
+
+	// nextEmit = s
+	MOVD R7, R10
+
+	// if s >= sLimit { goto emitRemainder }
+	MOVD R7, R3
+	SUB  R6, R3, R3
+	CMP  R3, R9
+	BLS  emitRemainder
+
+	// As per the encode_other.go code:
+	//
+	// We could immediately etc.
+
+	// x := load64(src, s-1)
+	MOVD -1(R7), R14
+
+	// prevHash := hash(uint32(x>>0), shift)
+	MOVW R14, R11
+	MULW R16, R11, R11
+	LSRW R5, R11, R11
+
+	// table[prevHash] = uint16(s-1)
+	MOVD R7, R3
+	SUB  R6, R3, R3
+	SUB  $1, R3, R3
+
+	MOVHU R3, 0(R17)(R11<<1)
+
+	// currHash := hash(uint32(x>>8), shift)
+	LSR  $8, R14, R14
+	MOVW R14, R11
+	MULW R16, R11, R11
+	LSRW R5, R11, R11
+
+	// candidate = int(table[currHash])
+	MOVHU 0(R17)(R11<<1), R15
+
+	// table[currHash] = uint16(s)
+	ADD   $1, R3, R3
+	MOVHU R3, 0(R17)(R11<<1)
+
+	// if uint32(x>>8) == load32(src, candidate) { continue }
+	MOVW (R6)(R15), R4
+	CMPW R4, R14
+	BEQ  inner1
+
+	// nextHash = hash(uint32(x>>16), shift)
+	LSR  $8, R14, R14
+	MOVW R14, R11
+	MULW R16, R11, R11
+	LSRW R5, R11, R11
+
+	// s++
+	ADD $1, R7, R7
+
+	// break out of the inner1 for loop, i.e. continue the outer loop.
+	B outer
+
+emitRemainder:
+	// if nextEmit < len(src) { etc }
+	MOVD src_len+32(FP), R3
+	ADD  R6, R3, R3
+	CMP  R3, R10
+	BEQ  encodeBlockEnd
+
+	// d += emitLiteral(dst[d:], src[nextEmit:])
+	//
+	// Push args.
+	MOVD R8, 8(RSP)
+	MOVD $0, 16(RSP)  // Unnecessary, as the callee ignores it, but conservative.
+	MOVD $0, 24(RSP)  // Unnecessary, as the callee ignores it, but conservative.
+	MOVD R10, 32(RSP)
+	SUB  R10, R3, R3
+	MOVD R3, 40(RSP)
+	MOVD R3, 48(RSP)  // Unnecessary, as the callee ignores it, but conservative.
+
+	// Spill local variables (registers) onto the stack; call; unspill.
+	MOVD R8, 88(RSP)
+	CALL ·emitLiteral(SB)
+	MOVD 88(RSP), R8
+
+	// Finish the "d +=" part of "d += emitLiteral(etc)".
+	MOVD 56(RSP), R1
+	ADD  R1, R8, R8
+
+encodeBlockEnd:
+	MOVD dst_base+0(FP), R3
+	SUB  R3, R8, R8
+	MOVD R8, d+48(FP)
+	RET

vendor/github.com/golang/snappy/encode_asm.go

@@ -0,0 +1,30 @@
+// Copyright 2016 The Snappy-Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !appengine
+// +build gc
+// +build !noasm
+// +build amd64 arm64
+
+package snappy
+
+// emitLiteral has the same semantics as in encode_other.go.
+//
+//go:noescape
+func emitLiteral(dst, lit []byte) int
+
+// emitCopy has the same semantics as in encode_other.go.
+//
+//go:noescape
+func emitCopy(dst []byte, offset, length int) int
+
+// extendMatch has the same semantics as in encode_other.go.
+//
+//go:noescape
+func extendMatch(src []byte, i, j int) int
+
+// encodeBlock has the same semantics as in encode_other.go.
+//
+//go:noescape
+func encodeBlock(dst, src []byte) (d int)

vendor/github.com/golang/snappy/encode_other.go

@@ -0,0 +1,238 @@
+// Copyright 2016 The Snappy-Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !amd64,!arm64 appengine !gc noasm
+
+package snappy
+
+func load32(b []byte, i int) uint32 {
+	b = b[i : i+4 : len(b)] // Help the compiler eliminate bounds checks on the next line.
+	return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
+}
+
+func load64(b []byte, i int) uint64 {
+	b = b[i : i+8 : len(b)] // Help the compiler eliminate bounds checks on the next line.
+	return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 |
+		uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
+}
+
+// emitLiteral writes a literal chunk and returns the number of bytes written.
+//
+// It assumes that:
+//	dst is long enough to hold the encoded bytes
+//	1 <= len(lit) && len(lit) <= 65536
+func emitLiteral(dst, lit []byte) int {
+	i, n := 0, uint(len(lit)-1)
+	switch {
+	case n < 60:
+		dst[0] = uint8(n)<<2 | tagLiteral
+		i = 1
+	case n < 1<<8:
+		dst[0] = 60<<2 | tagLiteral
+		dst[1] = uint8(n)
+		i = 2
+	default:
+		dst[0] = 61<<2 | tagLiteral
+		dst[1] = uint8(n)
+		dst[2] = uint8(n >> 8)
+		i = 3
+	}
+	return i + copy(dst[i:], lit)
+}
+
+// emitCopy writes a copy chunk and returns the number of bytes written.
+//
+// It assumes that:
+//	dst is long enough to hold the encoded bytes
+//	1 <= offset && offset <= 65535
+//	4 <= length && length <= 65535
+func emitCopy(dst []byte, offset, length int) int {
+	i := 0
+	// The maximum length for a single tagCopy1 or tagCopy2 op is 64 bytes. The
+	// threshold for this loop is a little higher (at 68 = 64 + 4), and the
+	// length emitted down below is is a little lower (at 60 = 64 - 4), because
+	// it's shorter to encode a length 67 copy as a length 60 tagCopy2 followed
+	// by a length 7 tagCopy1 (which encodes as 3+2 bytes) than to encode it as
+	// a length 64 tagCopy2 followed by a length 3 tagCopy2 (which encodes as
+	// 3+3 bytes). The magic 4 in the 64±4 is because the minimum length for a
+	// tagCopy1 op is 4 bytes, which is why a length 3 copy has to be an
+	// encodes-as-3-bytes tagCopy2 instead of an encodes-as-2-bytes tagCopy1.
+	for length >= 68 {
+		// Emit a length 64 copy, encoded as 3 bytes.
+		dst[i+0] = 63<<2 | tagCopy2
+		dst[i+1] = uint8(offset)
+		dst[i+2] = uint8(offset >> 8)
+		i += 3
+		length -= 64
+	}
+	if length > 64 {
+		// Emit a length 60 copy, encoded as 3 bytes.
+		dst[i+0] = 59<<2 | tagCopy2
+		dst[i+1] = uint8(offset)
+		dst[i+2] = uint8(offset >> 8)
+		i += 3
+		length -= 60
+	}
+	if length >= 12 || offset >= 2048 {
+		// Emit the remaining copy, encoded as 3 bytes.
+		dst[i+0] = uint8(length-1)<<2 | tagCopy2
+		dst[i+1] = uint8(offset)
+		dst[i+2] = uint8(offset >> 8)
+		return i + 3
+	}
+	// Emit the remaining copy, encoded as 2 bytes.
+	dst[i+0] = uint8(offset>>8)<<5 | uint8(length-4)<<2 | tagCopy1
+	dst[i+1] = uint8(offset)
+	return i + 2
+}
+
+// extendMatch returns the largest k such that k <= len(src) and that
+// src[i:i+k-j] and src[j:k] have the same contents.
+//
+// It assumes that:
+//	0 <= i && i < j && j <= len(src)
+func extendMatch(src []byte, i, j int) int {
+	for ; j < len(src) && src[i] == src[j]; i, j = i+1, j+1 {
+	}
+	return j
+}
+
+func hash(u, shift uint32) uint32 {
+	return (u * 0x1e35a7bd) >> shift
+}
+
+// encodeBlock encodes a non-empty src to a guaranteed-large-enough dst. It
+// assumes that the varint-encoded length of the decompressed bytes has already
+// been written.
+//
+// It also assumes that:
+//	len(dst) >= MaxEncodedLen(len(src)) &&
+// 	minNonLiteralBlockSize <= len(src) && len(src) <= maxBlockSize
+func encodeBlock(dst, src []byte) (d int) {
+	// Initialize the hash table. Its size ranges from 1<<8 to 1<<14 inclusive.
+	// The table element type is uint16, as s < sLimit and sLimit < len(src)
+	// and len(src) <= maxBlockSize and maxBlockSize == 65536.
+	const (
+		maxTableSize = 1 << 14
+		// tableMask is redundant, but helps the compiler eliminate bounds
+		// checks.
+		tableMask = maxTableSize - 1
+	)
+	shift := uint32(32 - 8)
+	for tableSize := 1 << 8; tableSize < maxTableSize && tableSize < len(src); tableSize *= 2 {
+		shift--
+	}
+	// In Go, all array elements are zero-initialized, so there is no advantage
+	// to a smaller tableSize per se. However, it matches the C++ algorithm,
+	// and in the asm versions of this code, we can get away with zeroing only
+	// the first tableSize elements.
+	var table [maxTableSize]uint16
+
+	// sLimit is when to stop looking for offset/length copies. The inputMargin
+	// lets us use a fast path for emitLiteral in the main loop, while we are
+	// looking for copies.
+	sLimit := len(src) - inputMargin
+
+	// nextEmit is where in src the next emitLiteral should start from.
+	nextEmit := 0
+
+	// The encoded form must start with a literal, as there are no previous
+	// bytes to copy, so we start looking for hash matches at s == 1.
+	s := 1
+	nextHash := hash(load32(src, s), shift)
+
+	for {
+		// Copied from the C++ snappy implementation:
+		//
+		// Heuristic match skipping: If 32 bytes are scanned with no matches
+		// found, start looking only at every other byte. If 32 more bytes are
+		// scanned (or skipped), look at every third byte, etc.. When a match
+		// is found, immediately go back to looking at every byte. This is a
+		// small loss (~5% performance, ~0.1% density) for compressible data
+		// due to more bookkeeping, but for non-compressible data (such as
+		// JPEG) it's a huge win since the compressor quickly "realizes" the
+		// data is incompressible and doesn't bother looking for matches
+		// everywhere.
+		//
+		// The "skip" variable keeps track of how many bytes there are since
+		// the last match; dividing it by 32 (ie. right-shifting by five) gives
+		// the number of bytes to move ahead for each iteration.
+		skip := 32
+
+		nextS := s
+		candidate := 0
+		for {
+			s = nextS
+			bytesBetweenHashLookups := skip >> 5
+			nextS = s + bytesBetweenHashLookups
+			skip += bytesBetweenHashLookups
+			if nextS > sLimit {
+				goto emitRemainder
+			}
+			candidate = int(table[nextHash&tableMask])
+			table[nextHash&tableMask] = uint16(s)
+			nextHash = hash(load32(src, nextS), shift)
+			if load32(src, s) == load32(src, candidate) {
+				break
+			}
+		}
+
+		// A 4-byte match has been found. We'll later see if more than 4 bytes
+		// match. But, prior to the match, src[nextEmit:s] are unmatched. Emit
+		// them as literal bytes.
+		d += emitLiteral(dst[d:], src[nextEmit:s])
+
+		// Call emitCopy, and then see if another emitCopy could be our next
+		// move. Repeat until we find no match for the input immediately after
+		// what was consumed by the last emitCopy call.
+		//
+		// If we exit this loop normally then we need to call emitLiteral next,
+		// though we don't yet know how big the literal will be. We handle that
+		// by proceeding to the next iteration of the main loop. We also can
+		// exit this loop via goto if we get close to exhausting the input.
+		for {
+			// Invariant: we have a 4-byte match at s, and no need to emit any
+			// literal bytes prior to s.
+			base := s
+
+			// Extend the 4-byte match as long as possible.
+			//
+			// This is an inlined version of:
+			//	s = extendMatch(src, candidate+4, s+4)
+			s += 4
+			for i := candidate + 4; s < len(src) && src[i] == src[s]; i, s = i+1, s+1 {
+			}
+
+			d += emitCopy(dst[d:], base-candidate, s-base)
+			nextEmit = s
+			if s >= sLimit {
+				goto emitRemainder
+			}
+
+			// We could immediately start working at s now, but to improve
+			// compression we first update the hash table at s-1 and at s. If
+			// another emitCopy is not our next move, also calculate nextHash
+			// at s+1. At least on GOARCH=amd64, these three hash calculations
+			// are faster as one load64 call (with some shifts) instead of
+			// three load32 calls.
+			x := load64(src, s-1)
+			prevHash := hash(uint32(x>>0), shift)
+			table[prevHash&tableMask] = uint16(s - 1)
+			currHash := hash(uint32(x>>8), shift)
+			candidate = int(table[currHash&tableMask])
+			table[currHash&tableMask] = uint16(s)
+			if uint32(x>>8) != load32(src, candidate) {
+				nextHash = hash(uint32(x>>16), shift)
+				s++
+				break
+			}
+		}
+	}
+
+emitRemainder:
+	if nextEmit < len(src) {
+		d += emitLiteral(dst[d:], src[nextEmit:])
+	}
+	return d
+}

vendor/github.com/golang/snappy/snappy.go

@@ -0,0 +1,98 @@
+// Copyright 2011 The Snappy-Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package snappy implements the Snappy compression format. It aims for very
+// high speeds and reasonable compression.
+//
+// There are actually two Snappy formats: block and stream. They are related,
+// but different: trying to decompress block-compressed data as a Snappy stream
+// will fail, and vice versa. The block format is the Decode and Encode
+// functions and the stream format is the Reader and Writer types.
+//
+// The block format, the more common case, is used when the complete size (the
+// number of bytes) of the original data is known upfront, at the time
+// compression starts. The stream format, also known as the framing format, is
+// for when that isn't always true.
+//
+// The canonical, C++ implementation is at https://github.com/google/snappy and
+// it only implements the block format.
+package snappy // import "github.com/golang/snappy"
+
+import (
+	"hash/crc32"
+)
+
+/*
+Each encoded block begins with the varint-encoded length of the decoded data,
+followed by a sequence of chunks. Chunks begin and end on byte boundaries. The
+first byte of each chunk is broken into its 2 least and 6 most significant bits
+called l and m: l ranges in [0, 4) and m ranges in [0, 64). l is the chunk tag.
+Zero means a literal tag. All other values mean a copy tag.
+
+For literal tags:
+  - If m < 60, the next 1 + m bytes are literal bytes.
+  - Otherwise, let n be the little-endian unsigned integer denoted by the next
+    m - 59 bytes. The next 1 + n bytes after that are literal bytes.
+
+For copy tags, length bytes are copied from offset bytes ago, in the style of
+Lempel-Ziv compression algorithms. In particular:
+  - For l == 1, the offset ranges in [0, 1<<11) and the length in [4, 12).
+    The length is 4 + the low 3 bits of m. The high 3 bits of m form bits 8-10
+    of the offset. The next byte is bits 0-7 of the offset.
+  - For l == 2, the offset ranges in [0, 1<<16) and the length in [1, 65).
+    The length is 1 + m. The offset is the little-endian unsigned integer
+    denoted by the next 2 bytes.
+  - For l == 3, this tag is a legacy format that is no longer issued by most
+    encoders. Nonetheless, the offset ranges in [0, 1<<32) and the length in
+    [1, 65). The length is 1 + m. The offset is the little-endian unsigned
+    integer denoted by the next 4 bytes.
+*/
+const (
+	tagLiteral = 0x00
+	tagCopy1   = 0x01
+	tagCopy2   = 0x02
+	tagCopy4   = 0x03
+)
+
+const (
+	checksumSize    = 4
+	chunkHeaderSize = 4
+	magicChunk      = "\xff\x06\x00\x00" + magicBody
+	magicBody       = "sNaPpY"
+
+	// maxBlockSize is the maximum size of the input to encodeBlock. It is not
+	// part of the wire format per se, but some parts of the encoder assume
+	// that an offset fits into a uint16.
+	//
+	// Also, for the framing format (Writer type instead of Encode function),
+	// https://github.com/google/snappy/blob/master/framing_format.txt says
+	// that "the uncompressed data in a chunk must be no longer than 65536
+	// bytes".
+	maxBlockSize = 65536
+
+	// maxEncodedLenOfMaxBlockSize equals MaxEncodedLen(maxBlockSize), but is
+	// hard coded to be a const instead of a variable, so that obufLen can also
+	// be a const. Their equivalence is confirmed by
+	// TestMaxEncodedLenOfMaxBlockSize.
+	maxEncodedLenOfMaxBlockSize = 76490
+
+	obufHeaderLen = len(magicChunk) + checksumSize + chunkHeaderSize
+	obufLen       = obufHeaderLen + maxEncodedLenOfMaxBlockSize
+)
+
+const (
+	chunkTypeCompressedData   = 0x00
+	chunkTypeUncompressedData = 0x01
+	chunkTypePadding          = 0xfe
+	chunkTypeStreamIdentifier = 0xff
+)
+
+var crcTable = crc32.MakeTable(crc32.Castagnoli)
+
+// crc implements the checksum specified in section 3 of
+// https://github.com/google/snappy/blob/master/framing_format.txt
+func crc(b []byte) uint32 {
+	c := crc32.Update(0, crcTable, b)
+	return uint32(c>>15|c<<17) + 0xa282ead8
+}

vendor/github.com/syndtr/goleveldb/LICENSE

@@ -0,0 +1,24 @@
+Copyright 2012 Suryandaru Triandana <syndtr@gmail.com>
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+    * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+    * Redistributions in binary form must reproduce the above copyright
+notice, this list of conditions and the following disclaimer in the
+documentation and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

vendor/github.com/syndtr/goleveldb/leveldb/batch.go

@@ -0,0 +1,349 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+
+	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/memdb"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+)
+
+// ErrBatchCorrupted records reason of batch corruption. This error will be
+// wrapped with errors.ErrCorrupted.
+type ErrBatchCorrupted struct {
+	Reason string
+}
+
+func (e *ErrBatchCorrupted) Error() string {
+	return fmt.Sprintf("leveldb: batch corrupted: %s", e.Reason)
+}
+
+func newErrBatchCorrupted(reason string) error {
+	return errors.NewErrCorrupted(storage.FileDesc{}, &ErrBatchCorrupted{reason})
+}
+
+const (
+	batchHeaderLen = 8 + 4
+	batchGrowRec   = 3000
+	batchBufioSize = 16
+)
+
+// BatchReplay wraps basic batch operations.
+type BatchReplay interface {
+	Put(key, value []byte)
+	Delete(key []byte)
+}
+
+type batchIndex struct {
+	keyType            keyType
+	keyPos, keyLen     int
+	valuePos, valueLen int
+}
+
+func (index batchIndex) k(data []byte) []byte {
+	return data[index.keyPos : index.keyPos+index.keyLen]
+}
+
+func (index batchIndex) v(data []byte) []byte {
+	if index.valueLen != 0 {
+		return data[index.valuePos : index.valuePos+index.valueLen]
+	}
+	return nil
+}
+
+func (index batchIndex) kv(data []byte) (key, value []byte) {
+	return index.k(data), index.v(data)
+}
+
+// Batch is a write batch.
+type Batch struct {
+	data  []byte
+	index []batchIndex
+
+	// internalLen is sums of key/value pair length plus 8-bytes internal key.
+	internalLen int
+}
+
+func (b *Batch) grow(n int) {
+	o := len(b.data)
+	if cap(b.data)-o < n {
+		div := 1
+		if len(b.index) > batchGrowRec {
+			div = len(b.index) / batchGrowRec
+		}
+		ndata := make([]byte, o, o+n+o/div)
+		copy(ndata, b.data)
+		b.data = ndata
+	}
+}
+
+func (b *Batch) appendRec(kt keyType, key, value []byte) {
+	n := 1 + binary.MaxVarintLen32 + len(key)
+	if kt == keyTypeVal {
+		n += binary.MaxVarintLen32 + len(value)
+	}
+	b.grow(n)
+	index := batchIndex{keyType: kt}
+	o := len(b.data)
+	data := b.data[:o+n]
+	data[o] = byte(kt)
+	o++
+	o += binary.PutUvarint(data[o:], uint64(len(key)))
+	index.keyPos = o
+	index.keyLen = len(key)
+	o += copy(data[o:], key)
+	if kt == keyTypeVal {
+		o += binary.PutUvarint(data[o:], uint64(len(value)))
+		index.valuePos = o
+		index.valueLen = len(value)
+		o += copy(data[o:], value)
+	}
+	b.data = data[:o]
+	b.index = append(b.index, index)
+	b.internalLen += index.keyLen + index.valueLen + 8
+}
+
+// Put appends 'put operation' of the given key/value pair to the batch.
+// It is safe to modify the contents of the argument after Put returns but not
+// before.
+func (b *Batch) Put(key, value []byte) {
+	b.appendRec(keyTypeVal, key, value)
+}
+
+// Delete appends 'delete operation' of the given key to the batch.
+// It is safe to modify the contents of the argument after Delete returns but
+// not before.
+func (b *Batch) Delete(key []byte) {
+	b.appendRec(keyTypeDel, key, nil)
+}
+
+// Dump dumps batch contents. The returned slice can be loaded into the
+// batch using Load method.
+// The returned slice is not its own copy, so the contents should not be
+// modified.
+func (b *Batch) Dump() []byte {
+	return b.data
+}
+
+// Load loads given slice into the batch. Previous contents of the batch
+// will be discarded.
+// The given slice will not be copied and will be used as batch buffer, so
+// it is not safe to modify the contents of the slice.
+func (b *Batch) Load(data []byte) error {
+	return b.decode(data, -1)
+}
+
+// Replay replays batch contents.
+func (b *Batch) Replay(r BatchReplay) error {
+	for _, index := range b.index {
+		switch index.keyType {
+		case keyTypeVal:
+			r.Put(index.k(b.data), index.v(b.data))
+		case keyTypeDel:
+			r.Delete(index.k(b.data))
+		}
+	}
+	return nil
+}
+
+// Len returns number of records in the batch.
+func (b *Batch) Len() int {
+	return len(b.index)
+}
+
+// Reset resets the batch.
+func (b *Batch) Reset() {
+	b.data = b.data[:0]
+	b.index = b.index[:0]
+	b.internalLen = 0
+}
+
+func (b *Batch) replayInternal(fn func(i int, kt keyType, k, v []byte) error) error {
+	for i, index := range b.index {
+		if err := fn(i, index.keyType, index.k(b.data), index.v(b.data)); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (b *Batch) append(p *Batch) {
+	ob := len(b.data)
+	oi := len(b.index)
+	b.data = append(b.data, p.data...)
+	b.index = append(b.index, p.index...)
+	b.internalLen += p.internalLen
+
+	// Updating index offset.
+	if ob != 0 {
+		for ; oi < len(b.index); oi++ {
+			index := &b.index[oi]
+			index.keyPos += ob
+			if index.valueLen != 0 {
+				index.valuePos += ob
+			}
+		}
+	}
+}
+
+func (b *Batch) decode(data []byte, expectedLen int) error {
+	b.data = data
+	b.index = b.index[:0]
+	b.internalLen = 0
+	err := decodeBatch(data, func(i int, index batchIndex) error {
+		b.index = append(b.index, index)
+		b.internalLen += index.keyLen + index.valueLen + 8
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+	if expectedLen >= 0 && len(b.index) != expectedLen {
+		return newErrBatchCorrupted(fmt.Sprintf("invalid records length: %d vs %d", expectedLen, len(b.index)))
+	}
+	return nil
+}
+
+func (b *Batch) putMem(seq uint64, mdb *memdb.DB) error {
+	var ik []byte
+	for i, index := range b.index {
+		ik = makeInternalKey(ik, index.k(b.data), seq+uint64(i), index.keyType)
+		if err := mdb.Put(ik, index.v(b.data)); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (b *Batch) revertMem(seq uint64, mdb *memdb.DB) error {
+	var ik []byte
+	for i, index := range b.index {
+		ik = makeInternalKey(ik, index.k(b.data), seq+uint64(i), index.keyType)
+		if err := mdb.Delete(ik); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func newBatch() interface{} {
+	return &Batch{}
+}
+
+func decodeBatch(data []byte, fn func(i int, index batchIndex) error) error {
+	var index batchIndex
+	for i, o := 0, 0; o < len(data); i++ {
+		// Key type.
+		index.keyType = keyType(data[o])
+		if index.keyType > keyTypeVal {
+			return newErrBatchCorrupted(fmt.Sprintf("bad record: invalid type %#x", uint(index.keyType)))
+		}
+		o++
+
+		// Key.
+		x, n := binary.Uvarint(data[o:])
+		o += n
+		if n <= 0 || o+int(x) > len(data) {
+			return newErrBatchCorrupted("bad record: invalid key length")
+		}
+		index.keyPos = o
+		index.keyLen = int(x)
+		o += index.keyLen
+
+		// Value.
+		if index.keyType == keyTypeVal {
+			x, n = binary.Uvarint(data[o:])
+			o += n
+			if n <= 0 || o+int(x) > len(data) {
+				return newErrBatchCorrupted("bad record: invalid value length")
+			}
+			index.valuePos = o
+			index.valueLen = int(x)
+			o += index.valueLen
+		} else {
+			index.valuePos = 0
+			index.valueLen = 0
+		}
+
+		if err := fn(i, index); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func decodeBatchToMem(data []byte, expectSeq uint64, mdb *memdb.DB) (seq uint64, batchLen int, err error) {
+	seq, batchLen, err = decodeBatchHeader(data)
+	if err != nil {
+		return 0, 0, err
+	}
+	if seq < expectSeq {
+		return 0, 0, newErrBatchCorrupted("invalid sequence number")
+	}
+	data = data[batchHeaderLen:]
+	var ik []byte
+	var decodedLen int
+	err = decodeBatch(data, func(i int, index batchIndex) error {
+		if i >= batchLen {
+			return newErrBatchCorrupted("invalid records length")
+		}
+		ik = makeInternalKey(ik, index.k(data), seq+uint64(i), index.keyType)
+		if err := mdb.Put(ik, index.v(data)); err != nil {
+			return err
+		}
+		decodedLen++
+		return nil
+	})
+	if err == nil && decodedLen != batchLen {
+		err = newErrBatchCorrupted(fmt.Sprintf("invalid records length: %d vs %d", batchLen, decodedLen))
+	}
+	return
+}
+
+func encodeBatchHeader(dst []byte, seq uint64, batchLen int) []byte {
+	dst = ensureBuffer(dst, batchHeaderLen)
+	binary.LittleEndian.PutUint64(dst, seq)
+	binary.LittleEndian.PutUint32(dst[8:], uint32(batchLen))
+	return dst
+}
+
+func decodeBatchHeader(data []byte) (seq uint64, batchLen int, err error) {
+	if len(data) < batchHeaderLen {
+		return 0, 0, newErrBatchCorrupted("too short")
+	}
+
+	seq = binary.LittleEndian.Uint64(data)
+	batchLen = int(binary.LittleEndian.Uint32(data[8:]))
+	if batchLen < 0 {
+		return 0, 0, newErrBatchCorrupted("invalid records length")
+	}
+	return
+}
+
+func batchesLen(batches []*Batch) int {
+	batchLen := 0
+	for _, batch := range batches {
+		batchLen += batch.Len()
+	}
+	return batchLen
+}
+
+func writeBatchesWithHeader(wr io.Writer, batches []*Batch, seq uint64) error {
+	if _, err := wr.Write(encodeBatchHeader(nil, seq, batchesLen(batches))); err != nil {
+		return err
+	}
+	for _, batch := range batches {
+		if _, err := wr.Write(batch.data); err != nil {
+			return err
+		}
+	}
+	return nil
+}

vendor/github.com/syndtr/goleveldb/leveldb/cache/cache.go

@@ -0,0 +1,704 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Package cache provides interface and implementation of a cache algorithms.
+package cache
+
+import (
+	"sync"
+	"sync/atomic"
+	"unsafe"
+
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+// Cacher provides interface to implements a caching functionality.
+// An implementation must be safe for concurrent use.
+type Cacher interface {
+	// Capacity returns cache capacity.
+	Capacity() int
+
+	// SetCapacity sets cache capacity.
+	SetCapacity(capacity int)
+
+	// Promote promotes the 'cache node'.
+	Promote(n *Node)
+
+	// Ban evicts the 'cache node' and prevent subsequent 'promote'.
+	Ban(n *Node)
+
+	// Evict evicts the 'cache node'.
+	Evict(n *Node)
+
+	// EvictNS evicts 'cache node' with the given namespace.
+	EvictNS(ns uint64)
+
+	// EvictAll evicts all 'cache node'.
+	EvictAll()
+
+	// Close closes the 'cache tree'
+	Close() error
+}
+
+// Value is a 'cacheable object'. It may implements util.Releaser, if
+// so the the Release method will be called once object is released.
+type Value interface{}
+
+// NamespaceGetter provides convenient wrapper for namespace.
+type NamespaceGetter struct {
+	Cache *Cache
+	NS    uint64
+}
+
+// Get simply calls Cache.Get() method.
+func (g *NamespaceGetter) Get(key uint64, setFunc func() (size int, value Value)) *Handle {
+	return g.Cache.Get(g.NS, key, setFunc)
+}
+
+// The hash tables implementation is based on:
+// "Dynamic-Sized Nonblocking Hash Tables", by Yujie Liu,
+// Kunlong Zhang, and Michael Spear.
+// ACM Symposium on Principles of Distributed Computing, Jul 2014.
+
+const (
+	mInitialSize           = 1 << 4
+	mOverflowThreshold     = 1 << 5
+	mOverflowGrowThreshold = 1 << 7
+)
+
+type mBucket struct {
+	mu     sync.Mutex
+	node   []*Node
+	frozen bool
+}
+
+func (b *mBucket) freeze() []*Node {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if !b.frozen {
+		b.frozen = true
+	}
+	return b.node
+}
+
+func (b *mBucket) get(r *Cache, h *mNode, hash uint32, ns, key uint64, noset bool) (done, added bool, n *Node) {
+	b.mu.Lock()
+
+	if b.frozen {
+		b.mu.Unlock()
+		return
+	}
+
+	// Scan the node.
+	for _, n := range b.node {
+		if n.hash == hash && n.ns == ns && n.key == key {
+			atomic.AddInt32(&n.ref, 1)
+			b.mu.Unlock()
+			return true, false, n
+		}
+	}
+
+	// Get only.
+	if noset {
+		b.mu.Unlock()
+		return true, false, nil
+	}
+
+	// Create node.
+	n = &Node{
+		r:    r,
+		hash: hash,
+		ns:   ns,
+		key:  key,
+		ref:  1,
+	}
+	// Add node to bucket.
+	b.node = append(b.node, n)
+	bLen := len(b.node)
+	b.mu.Unlock()
+
+	// Update counter.
+	grow := atomic.AddInt32(&r.nodes, 1) >= h.growThreshold
+	if bLen > mOverflowThreshold {
+		grow = grow || atomic.AddInt32(&h.overflow, 1) >= mOverflowGrowThreshold
+	}
+
+	// Grow.
+	if grow && atomic.CompareAndSwapInt32(&h.resizeInProgess, 0, 1) {
+		nhLen := len(h.buckets) << 1
+		nh := &mNode{
+			buckets:         make([]unsafe.Pointer, nhLen),
+			mask:            uint32(nhLen) - 1,
+			pred:            unsafe.Pointer(h),
+			growThreshold:   int32(nhLen * mOverflowThreshold),
+			shrinkThreshold: int32(nhLen >> 1),
+		}
+		ok := atomic.CompareAndSwapPointer(&r.mHead, unsafe.Pointer(h), unsafe.Pointer(nh))
+		if !ok {
+			panic("BUG: failed swapping head")
+		}
+		go nh.initBuckets()
+	}
+
+	return true, true, n
+}
+
+func (b *mBucket) delete(r *Cache, h *mNode, hash uint32, ns, key uint64) (done, deleted bool) {
+	b.mu.Lock()
+
+	if b.frozen {
+		b.mu.Unlock()
+		return
+	}
+
+	// Scan the node.
+	var (
+		n    *Node
+		bLen int
+	)
+	for i := range b.node {
+		n = b.node[i]
+		if n.ns == ns && n.key == key {
+			if atomic.LoadInt32(&n.ref) == 0 {
+				deleted = true
+
+				// Call releaser.
+				if n.value != nil {
+					if r, ok := n.value.(util.Releaser); ok {
+						r.Release()
+					}
+					n.value = nil
+				}
+
+				// Remove node from bucket.
+				b.node = append(b.node[:i], b.node[i+1:]...)
+				bLen = len(b.node)
+			}
+			break
+		}
+	}
+	b.mu.Unlock()
+
+	if deleted {
+		// Call OnDel.
+		for _, f := range n.onDel {
+			f()
+		}
+
+		// Update counter.
+		atomic.AddInt32(&r.size, int32(n.size)*-1)
+		shrink := atomic.AddInt32(&r.nodes, -1) < h.shrinkThreshold
+		if bLen >= mOverflowThreshold {
+			atomic.AddInt32(&h.overflow, -1)
+		}
+
+		// Shrink.
+		if shrink && len(h.buckets) > mInitialSize && atomic.CompareAndSwapInt32(&h.resizeInProgess, 0, 1) {
+			nhLen := len(h.buckets) >> 1
+			nh := &mNode{
+				buckets:         make([]unsafe.Pointer, nhLen),
+				mask:            uint32(nhLen) - 1,
+				pred:            unsafe.Pointer(h),
+				growThreshold:   int32(nhLen * mOverflowThreshold),
+				shrinkThreshold: int32(nhLen >> 1),
+			}
+			ok := atomic.CompareAndSwapPointer(&r.mHead, unsafe.Pointer(h), unsafe.Pointer(nh))
+			if !ok {
+				panic("BUG: failed swapping head")
+			}
+			go nh.initBuckets()
+		}
+	}
+
+	return true, deleted
+}
+
+type mNode struct {
+	buckets         []unsafe.Pointer // []*mBucket
+	mask            uint32
+	pred            unsafe.Pointer // *mNode
+	resizeInProgess int32
+
+	overflow        int32
+	growThreshold   int32
+	shrinkThreshold int32
+}
+
+func (n *mNode) initBucket(i uint32) *mBucket {
+	if b := (*mBucket)(atomic.LoadPointer(&n.buckets[i])); b != nil {
+		return b
+	}
+
+	p := (*mNode)(atomic.LoadPointer(&n.pred))
+	if p != nil {
+		var node []*Node
+		if n.mask > p.mask {
+			// Grow.
+			pb := (*mBucket)(atomic.LoadPointer(&p.buckets[i&p.mask]))
+			if pb == nil {
+				pb = p.initBucket(i & p.mask)
+			}
+			m := pb.freeze()
+			// Split nodes.
+			for _, x := range m {
+				if x.hash&n.mask == i {
+					node = append(node, x)
+				}
+			}
+		} else {
+			// Shrink.
+			pb0 := (*mBucket)(atomic.LoadPointer(&p.buckets[i]))
+			if pb0 == nil {
+				pb0 = p.initBucket(i)
+			}
+			pb1 := (*mBucket)(atomic.LoadPointer(&p.buckets[i+uint32(len(n.buckets))]))
+			if pb1 == nil {
+				pb1 = p.initBucket(i + uint32(len(n.buckets)))
+			}
+			m0 := pb0.freeze()
+			m1 := pb1.freeze()
+			// Merge nodes.
+			node = make([]*Node, 0, len(m0)+len(m1))
+			node = append(node, m0...)
+			node = append(node, m1...)
+		}
+		b := &mBucket{node: node}
+		if atomic.CompareAndSwapPointer(&n.buckets[i], nil, unsafe.Pointer(b)) {
+			if len(node) > mOverflowThreshold {
+				atomic.AddInt32(&n.overflow, int32(len(node)-mOverflowThreshold))
+			}
+			return b
+		}
+	}
+
+	return (*mBucket)(atomic.LoadPointer(&n.buckets[i]))
+}
+
+func (n *mNode) initBuckets() {
+	for i := range n.buckets {
+		n.initBucket(uint32(i))
+	}
+	atomic.StorePointer(&n.pred, nil)
+}
+
+// Cache is a 'cache map'.
+type Cache struct {
+	mu     sync.RWMutex
+	mHead  unsafe.Pointer // *mNode
+	nodes  int32
+	size   int32
+	cacher Cacher
+	closed bool
+}
+
+// NewCache creates a new 'cache map'. The cacher is optional and
+// may be nil.
+func NewCache(cacher Cacher) *Cache {
+	h := &mNode{
+		buckets:         make([]unsafe.Pointer, mInitialSize),
+		mask:            mInitialSize - 1,
+		growThreshold:   int32(mInitialSize * mOverflowThreshold),
+		shrinkThreshold: 0,
+	}
+	for i := range h.buckets {
+		h.buckets[i] = unsafe.Pointer(&mBucket{})
+	}
+	r := &Cache{
+		mHead:  unsafe.Pointer(h),
+		cacher: cacher,
+	}
+	return r
+}
+
+func (r *Cache) getBucket(hash uint32) (*mNode, *mBucket) {
+	h := (*mNode)(atomic.LoadPointer(&r.mHead))
+	i := hash & h.mask
+	b := (*mBucket)(atomic.LoadPointer(&h.buckets[i]))
+	if b == nil {
+		b = h.initBucket(i)
+	}
+	return h, b
+}
+
+func (r *Cache) delete(n *Node) bool {
+	for {
+		h, b := r.getBucket(n.hash)
+		done, deleted := b.delete(r, h, n.hash, n.ns, n.key)
+		if done {
+			return deleted
+		}
+	}
+}
+
+// Nodes returns number of 'cache node' in the map.
+func (r *Cache) Nodes() int {
+	return int(atomic.LoadInt32(&r.nodes))
+}
+
+// Size returns sums of 'cache node' size in the map.
+func (r *Cache) Size() int {
+	return int(atomic.LoadInt32(&r.size))
+}
+
+// Capacity returns cache capacity.
+func (r *Cache) Capacity() int {
+	if r.cacher == nil {
+		return 0
+	}
+	return r.cacher.Capacity()
+}
+
+// SetCapacity sets cache capacity.
+func (r *Cache) SetCapacity(capacity int) {
+	if r.cacher != nil {
+		r.cacher.SetCapacity(capacity)
+	}
+}
+
+// Get gets 'cache node' with the given namespace and key.
+// If cache node is not found and setFunc is not nil, Get will atomically creates
+// the 'cache node' by calling setFunc. Otherwise Get will returns nil.
+//
+// The returned 'cache handle' should be released after use by calling Release
+// method.
+func (r *Cache) Get(ns, key uint64, setFunc func() (size int, value Value)) *Handle {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	if r.closed {
+		return nil
+	}
+
+	hash := murmur32(ns, key, 0xf00)
+	for {
+		h, b := r.getBucket(hash)
+		done, _, n := b.get(r, h, hash, ns, key, setFunc == nil)
+		if done {
+			if n != nil {
+				n.mu.Lock()
+				if n.value == nil {
+					if setFunc == nil {
+						n.mu.Unlock()
+						n.unref()
+						return nil
+					}
+
+					n.size, n.value = setFunc()
+					if n.value == nil {
+						n.size = 0
+						n.mu.Unlock()
+						n.unref()
+						return nil
+					}
+					atomic.AddInt32(&r.size, int32(n.size))
+				}
+				n.mu.Unlock()
+				if r.cacher != nil {
+					r.cacher.Promote(n)
+				}
+				return &Handle{unsafe.Pointer(n)}
+			}
+
+			break
+		}
+	}
+	return nil
+}
+
+// Delete removes and ban 'cache node' with the given namespace and key.
+// A banned 'cache node' will never inserted into the 'cache tree'. Ban
+// only attributed to the particular 'cache node', so when a 'cache node'
+// is recreated it will not be banned.
+//
+// If onDel is not nil, then it will be executed if such 'cache node'
+// doesn't exist or once the 'cache node' is released.
+//
+// Delete return true is such 'cache node' exist.
+func (r *Cache) Delete(ns, key uint64, onDel func()) bool {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	if r.closed {
+		return false
+	}
+
+	hash := murmur32(ns, key, 0xf00)
+	for {
+		h, b := r.getBucket(hash)
+		done, _, n := b.get(r, h, hash, ns, key, true)
+		if done {
+			if n != nil {
+				if onDel != nil {
+					n.mu.Lock()
+					n.onDel = append(n.onDel, onDel)
+					n.mu.Unlock()
+				}
+				if r.cacher != nil {
+					r.cacher.Ban(n)
+				}
+				n.unref()
+				return true
+			}
+
+			break
+		}
+	}
+
+	if onDel != nil {
+		onDel()
+	}
+
+	return false
+}
+
+// Evict evicts 'cache node' with the given namespace and key. This will
+// simply call Cacher.Evict.
+//
+// Evict return true is such 'cache node' exist.
+func (r *Cache) Evict(ns, key uint64) bool {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	if r.closed {
+		return false
+	}
+
+	hash := murmur32(ns, key, 0xf00)
+	for {
+		h, b := r.getBucket(hash)
+		done, _, n := b.get(r, h, hash, ns, key, true)
+		if done {
+			if n != nil {
+				if r.cacher != nil {
+					r.cacher.Evict(n)
+				}
+				n.unref()
+				return true
+			}
+
+			break
+		}
+	}
+
+	return false
+}
+
+// EvictNS evicts 'cache node' with the given namespace. This will
+// simply call Cacher.EvictNS.
+func (r *Cache) EvictNS(ns uint64) {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	if r.closed {
+		return
+	}
+
+	if r.cacher != nil {
+		r.cacher.EvictNS(ns)
+	}
+}
+
+// EvictAll evicts all 'cache node'. This will simply call Cacher.EvictAll.
+func (r *Cache) EvictAll() {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	if r.closed {
+		return
+	}
+
+	if r.cacher != nil {
+		r.cacher.EvictAll()
+	}
+}
+
+// Close closes the 'cache map' and forcefully releases all 'cache node'.
+func (r *Cache) Close() error {
+	r.mu.Lock()
+	if !r.closed {
+		r.closed = true
+
+		h := (*mNode)(r.mHead)
+		h.initBuckets()
+
+		for i := range h.buckets {
+			b := (*mBucket)(h.buckets[i])
+			for _, n := range b.node {
+				// Call releaser.
+				if n.value != nil {
+					if r, ok := n.value.(util.Releaser); ok {
+						r.Release()
+					}
+					n.value = nil
+				}
+
+				// Call OnDel.
+				for _, f := range n.onDel {
+					f()
+				}
+				n.onDel = nil
+			}
+		}
+	}
+	r.mu.Unlock()
+
+	// Avoid deadlock.
+	if r.cacher != nil {
+		if err := r.cacher.Close(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// CloseWeak closes the 'cache map' and evict all 'cache node' from cacher, but
+// unlike Close it doesn't forcefully releases 'cache node'.
+func (r *Cache) CloseWeak() error {
+	r.mu.Lock()
+	if !r.closed {
+		r.closed = true
+	}
+	r.mu.Unlock()
+
+	// Avoid deadlock.
+	if r.cacher != nil {
+		r.cacher.EvictAll()
+		if err := r.cacher.Close(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Node is a 'cache node'.
+type Node struct {
+	r *Cache
+
+	hash    uint32
+	ns, key uint64
+
+	mu    sync.Mutex
+	size  int
+	value Value
+
+	ref   int32
+	onDel []func()
+
+	CacheData unsafe.Pointer
+}
+
+// NS returns this 'cache node' namespace.
+func (n *Node) NS() uint64 {
+	return n.ns
+}
+
+// Key returns this 'cache node' key.
+func (n *Node) Key() uint64 {
+	return n.key
+}
+
+// Size returns this 'cache node' size.
+func (n *Node) Size() int {
+	return n.size
+}
+
+// Value returns this 'cache node' value.
+func (n *Node) Value() Value {
+	return n.value
+}
+
+// Ref returns this 'cache node' ref counter.
+func (n *Node) Ref() int32 {
+	return atomic.LoadInt32(&n.ref)
+}
+
+// GetHandle returns an handle for this 'cache node'.
+func (n *Node) GetHandle() *Handle {
+	if atomic.AddInt32(&n.ref, 1) <= 1 {
+		panic("BUG: Node.GetHandle on zero ref")
+	}
+	return &Handle{unsafe.Pointer(n)}
+}
+
+func (n *Node) unref() {
+	if atomic.AddInt32(&n.ref, -1) == 0 {
+		n.r.delete(n)
+	}
+}
+
+func (n *Node) unrefLocked() {
+	if atomic.AddInt32(&n.ref, -1) == 0 {
+		n.r.mu.RLock()
+		if !n.r.closed {
+			n.r.delete(n)
+		}
+		n.r.mu.RUnlock()
+	}
+}
+
+// Handle is a 'cache handle' of a 'cache node'.
+type Handle struct {
+	n unsafe.Pointer // *Node
+}
+
+// Value returns the value of the 'cache node'.
+func (h *Handle) Value() Value {
+	n := (*Node)(atomic.LoadPointer(&h.n))
+	if n != nil {
+		return n.value
+	}
+	return nil
+}
+
+// Release releases this 'cache handle'.
+// It is safe to call release multiple times.
+func (h *Handle) Release() {
+	nPtr := atomic.LoadPointer(&h.n)
+	if nPtr != nil && atomic.CompareAndSwapPointer(&h.n, nPtr, nil) {
+		n := (*Node)(nPtr)
+		n.unrefLocked()
+	}
+}
+
+func murmur32(ns, key uint64, seed uint32) uint32 {
+	const (
+		m = uint32(0x5bd1e995)
+		r = 24
+	)
+
+	k1 := uint32(ns >> 32)
+	k2 := uint32(ns)
+	k3 := uint32(key >> 32)
+	k4 := uint32(key)
+
+	k1 *= m
+	k1 ^= k1 >> r
+	k1 *= m
+
+	k2 *= m
+	k2 ^= k2 >> r
+	k2 *= m
+
+	k3 *= m
+	k3 ^= k3 >> r
+	k3 *= m
+
+	k4 *= m
+	k4 ^= k4 >> r
+	k4 *= m
+
+	h := seed
+
+	h *= m
+	h ^= k1
+	h *= m
+	h ^= k2
+	h *= m
+	h ^= k3
+	h *= m
+	h ^= k4
+
+	h ^= h >> 13
+	h *= m
+	h ^= h >> 15
+
+	return h
+}

vendor/github.com/syndtr/goleveldb/leveldb/cache/lru.go

@@ -0,0 +1,195 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package cache
+
+import (
+	"sync"
+	"unsafe"
+)
+
+type lruNode struct {
+	n   *Node
+	h   *Handle
+	ban bool
+
+	next, prev *lruNode
+}
+
+func (n *lruNode) insert(at *lruNode) {
+	x := at.next
+	at.next = n
+	n.prev = at
+	n.next = x
+	x.prev = n
+}
+
+func (n *lruNode) remove() {
+	if n.prev != nil {
+		n.prev.next = n.next
+		n.next.prev = n.prev
+		n.prev = nil
+		n.next = nil
+	} else {
+		panic("BUG: removing removed node")
+	}
+}
+
+type lru struct {
+	mu       sync.Mutex
+	capacity int
+	used     int
+	recent   lruNode
+}
+
+func (r *lru) reset() {
+	r.recent.next = &r.recent
+	r.recent.prev = &r.recent
+	r.used = 0
+}
+
+func (r *lru) Capacity() int {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	return r.capacity
+}
+
+func (r *lru) SetCapacity(capacity int) {
+	var evicted []*lruNode
+
+	r.mu.Lock()
+	r.capacity = capacity
+	for r.used > r.capacity {
+		rn := r.recent.prev
+		if rn == nil {
+			panic("BUG: invalid LRU used or capacity counter")
+		}
+		rn.remove()
+		rn.n.CacheData = nil
+		r.used -= rn.n.Size()
+		evicted = append(evicted, rn)
+	}
+	r.mu.Unlock()
+
+	for _, rn := range evicted {
+		rn.h.Release()
+	}
+}
+
+func (r *lru) Promote(n *Node) {
+	var evicted []*lruNode
+
+	r.mu.Lock()
+	if n.CacheData == nil {
+		if n.Size() <= r.capacity {
+			rn := &lruNode{n: n, h: n.GetHandle()}
+			rn.insert(&r.recent)
+			n.CacheData = unsafe.Pointer(rn)
+			r.used += n.Size()
+
+			for r.used > r.capacity {
+				rn := r.recent.prev
+				if rn == nil {
+					panic("BUG: invalid LRU used or capacity counter")
+				}
+				rn.remove()
+				rn.n.CacheData = nil
+				r.used -= rn.n.Size()
+				evicted = append(evicted, rn)
+			}
+		}
+	} else {
+		rn := (*lruNode)(n.CacheData)
+		if !rn.ban {
+			rn.remove()
+			rn.insert(&r.recent)
+		}
+	}
+	r.mu.Unlock()
+
+	for _, rn := range evicted {
+		rn.h.Release()
+	}
+}
+
+func (r *lru) Ban(n *Node) {
+	r.mu.Lock()
+	if n.CacheData == nil {
+		n.CacheData = unsafe.Pointer(&lruNode{n: n, ban: true})
+	} else {
+		rn := (*lruNode)(n.CacheData)
+		if !rn.ban {
+			rn.remove()
+			rn.ban = true
+			r.used -= rn.n.Size()
+			r.mu.Unlock()
+
+			rn.h.Release()
+			rn.h = nil
+			return
+		}
+	}
+	r.mu.Unlock()
+}
+
+func (r *lru) Evict(n *Node) {
+	r.mu.Lock()
+	rn := (*lruNode)(n.CacheData)
+	if rn == nil || rn.ban {
+		r.mu.Unlock()
+		return
+	}
+	n.CacheData = nil
+	r.mu.Unlock()
+
+	rn.h.Release()
+}
+
+func (r *lru) EvictNS(ns uint64) {
+	var evicted []*lruNode
+
+	r.mu.Lock()
+	for e := r.recent.prev; e != &r.recent; {
+		rn := e
+		e = e.prev
+		if rn.n.NS() == ns {
+			rn.remove()
+			rn.n.CacheData = nil
+			r.used -= rn.n.Size()
+			evicted = append(evicted, rn)
+		}
+	}
+	r.mu.Unlock()
+
+	for _, rn := range evicted {
+		rn.h.Release()
+	}
+}
+
+func (r *lru) EvictAll() {
+	r.mu.Lock()
+	back := r.recent.prev
+	for rn := back; rn != &r.recent; rn = rn.prev {
+		rn.n.CacheData = nil
+	}
+	r.reset()
+	r.mu.Unlock()
+
+	for rn := back; rn != &r.recent; rn = rn.prev {
+		rn.h.Release()
+	}
+}
+
+func (r *lru) Close() error {
+	return nil
+}
+
+// NewLRU create a new LRU-cache.
+func NewLRU(capacity int) Cacher {
+	r := &lru{capacity: capacity}
+	r.reset()
+	return r
+}

vendor/github.com/syndtr/goleveldb/leveldb/comparer.go

@@ -0,0 +1,67 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"github.com/syndtr/goleveldb/leveldb/comparer"
+)
+
+type iComparer struct {
+	ucmp comparer.Comparer
+}
+
+func (icmp *iComparer) uName() string {
+	return icmp.ucmp.Name()
+}
+
+func (icmp *iComparer) uCompare(a, b []byte) int {
+	return icmp.ucmp.Compare(a, b)
+}
+
+func (icmp *iComparer) uSeparator(dst, a, b []byte) []byte {
+	return icmp.ucmp.Separator(dst, a, b)
+}
+
+func (icmp *iComparer) uSuccessor(dst, b []byte) []byte {
+	return icmp.ucmp.Successor(dst, b)
+}
+
+func (icmp *iComparer) Name() string {
+	return icmp.uName()
+}
+
+func (icmp *iComparer) Compare(a, b []byte) int {
+	x := icmp.uCompare(internalKey(a).ukey(), internalKey(b).ukey())
+	if x == 0 {
+		if m, n := internalKey(a).num(), internalKey(b).num(); m > n {
+			return -1
+		} else if m < n {
+			return 1
+		}
+	}
+	return x
+}
+
+func (icmp *iComparer) Separator(dst, a, b []byte) []byte {
+	ua, ub := internalKey(a).ukey(), internalKey(b).ukey()
+	dst = icmp.uSeparator(dst, ua, ub)
+	if dst != nil && len(dst) < len(ua) && icmp.uCompare(ua, dst) < 0 {
+		// Append earliest possible number.
+		return append(dst, keyMaxNumBytes...)
+	}
+	return nil
+}
+
+func (icmp *iComparer) Successor(dst, b []byte) []byte {
+	ub := internalKey(b).ukey()
+	dst = icmp.uSuccessor(dst, ub)
+	if dst != nil && len(dst) < len(ub) && icmp.uCompare(ub, dst) < 0 {
+		// Append earliest possible number.
+		return append(dst, keyMaxNumBytes...)
+	}
+	return nil
+}

vendor/github.com/syndtr/goleveldb/leveldb/comparer/bytes_comparer.go

@@ -0,0 +1,51 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package comparer
+
+import "bytes"
+
+type bytesComparer struct{}
+
+func (bytesComparer) Compare(a, b []byte) int {
+	return bytes.Compare(a, b)
+}
+
+func (bytesComparer) Name() string {
+	return "leveldb.BytewiseComparator"
+}
+
+func (bytesComparer) Separator(dst, a, b []byte) []byte {
+	i, n := 0, len(a)
+	if n > len(b) {
+		n = len(b)
+	}
+	for ; i < n && a[i] == b[i]; i++ {
+	}
+	if i >= n {
+		// Do not shorten if one string is a prefix of the other
+	} else if c := a[i]; c < 0xff && c+1 < b[i] {
+		dst = append(dst, a[:i+1]...)
+		dst[len(dst)-1]++
+		return dst
+	}
+	return nil
+}
+
+func (bytesComparer) Successor(dst, b []byte) []byte {
+	for i, c := range b {
+		if c != 0xff {
+			dst = append(dst, b[:i+1]...)
+			dst[len(dst)-1]++
+			return dst
+		}
+	}
+	return nil
+}
+
+// DefaultComparer are default implementation of the Comparer interface.
+// It uses the natural ordering, consistent with bytes.Compare.
+var DefaultComparer = bytesComparer{}

vendor/github.com/syndtr/goleveldb/leveldb/comparer/comparer.go

@@ -0,0 +1,57 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Package comparer provides interface and implementation for ordering
+// sets of data.
+package comparer
+
+// BasicComparer is the interface that wraps the basic Compare method.
+type BasicComparer interface {
+	// Compare returns -1, 0, or +1 depending on whether a is 'less than',
+	// 'equal to' or 'greater than' b. The two arguments can only be 'equal'
+	// if their contents are exactly equal. Furthermore, the empty slice
+	// must be 'less than' any non-empty slice.
+	Compare(a, b []byte) int
+}
+
+// Comparer defines a total ordering over the space of []byte keys: a 'less
+// than' relationship.
+type Comparer interface {
+	BasicComparer
+
+	// Name returns name of the comparer.
+	//
+	// The Level-DB on-disk format stores the comparer name, and opening a
+	// database with a different comparer from the one it was created with
+	// will result in an error.
+	//
+	// An implementation to a new name whenever the comparer implementation
+	// changes in a way that will cause the relative ordering of any two keys
+	// to change.
+	//
+	// Names starting with "leveldb." are reserved and should not be used
+	// by any users of this package.
+	Name() string
+
+	// Bellow are advanced functions used to reduce the space requirements
+	// for internal data structures such as index blocks.
+
+	// Separator appends a sequence of bytes x to dst such that a <= x && x < b,
+	// where 'less than' is consistent with Compare. An implementation should
+	// return nil if x equal to a.
+	//
+	// Either contents of a or b should not by any means modified. Doing so
+	// may cause corruption on the internal state.
+	Separator(dst, a, b []byte) []byte
+
+	// Successor appends a sequence of bytes x to dst such that x >= b, where
+	// 'less than' is consistent with Compare. An implementation should return
+	// nil if x equal to b.
+	//
+	// Contents of b should not by any means modified. Doing so may cause
+	// corruption on the internal state.
+	Successor(dst, b []byte) []byte
+}

vendor/github.com/syndtr/goleveldb/leveldb/db.go

@@ -0,0 +1,1179 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"container/list"
+	"fmt"
+	"io"
+	"os"
+	"runtime"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/iterator"
+	"github.com/syndtr/goleveldb/leveldb/journal"
+	"github.com/syndtr/goleveldb/leveldb/memdb"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+	"github.com/syndtr/goleveldb/leveldb/table"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+// DB is a LevelDB database.
+type DB struct {
+	// Need 64-bit alignment.
+	seq uint64
+
+	// Stats. Need 64-bit alignment.
+	cWriteDelay            int64 // The cumulative duration of write delays
+	cWriteDelayN           int32 // The cumulative number of write delays
+	inWritePaused          int32 // The indicator whether write operation is paused by compaction
+	aliveSnaps, aliveIters int32
+
+	// Session.
+	s *session
+
+	// MemDB.
+	memMu           sync.RWMutex
+	memPool         chan *memdb.DB
+	mem, frozenMem  *memDB
+	journal         *journal.Writer
+	journalWriter   storage.Writer
+	journalFd       storage.FileDesc
+	frozenJournalFd storage.FileDesc
+	frozenSeq       uint64
+
+	// Snapshot.
+	snapsMu   sync.Mutex
+	snapsList *list.List
+
+	// Write.
+	batchPool    sync.Pool
+	writeMergeC  chan writeMerge
+	writeMergedC chan bool
+	writeLockC   chan struct{}
+	writeAckC    chan error
+	writeDelay   time.Duration
+	writeDelayN  int
+	tr           *Transaction
+
+	// Compaction.
+	compCommitLk     sync.Mutex
+	tcompCmdC        chan cCmd
+	tcompPauseC      chan chan<- struct{}
+	mcompCmdC        chan cCmd
+	compErrC         chan error
+	compPerErrC      chan error
+	compErrSetC      chan error
+	compWriteLocking bool
+	compStats        cStats
+	memdbMaxLevel    int // For testing.
+
+	// Close.
+	closeW sync.WaitGroup
+	closeC chan struct{}
+	closed uint32
+	closer io.Closer
+}
+
+func openDB(s *session) (*DB, error) {
+	s.log("db@open opening")
+	start := time.Now()
+	db := &DB{
+		s: s,
+		// Initial sequence
+		seq: s.stSeqNum,
+		// MemDB
+		memPool: make(chan *memdb.DB, 1),
+		// Snapshot
+		snapsList: list.New(),
+		// Write
+		batchPool:    sync.Pool{New: newBatch},
+		writeMergeC:  make(chan writeMerge),
+		writeMergedC: make(chan bool),
+		writeLockC:   make(chan struct{}, 1),
+		writeAckC:    make(chan error),
+		// Compaction
+		tcompCmdC:   make(chan cCmd),
+		tcompPauseC: make(chan chan<- struct{}),
+		mcompCmdC:   make(chan cCmd),
+		compErrC:    make(chan error),
+		compPerErrC: make(chan error),
+		compErrSetC: make(chan error),
+		// Close
+		closeC: make(chan struct{}),
+	}
+
+	// Read-only mode.
+	readOnly := s.o.GetReadOnly()
+
+	if readOnly {
+		// Recover journals (read-only mode).
+		if err := db.recoverJournalRO(); err != nil {
+			return nil, err
+		}
+	} else {
+		// Recover journals.
+		if err := db.recoverJournal(); err != nil {
+			return nil, err
+		}
+
+		// Remove any obsolete files.
+		if err := db.checkAndCleanFiles(); err != nil {
+			// Close journal.
+			if db.journal != nil {
+				db.journal.Close()
+				db.journalWriter.Close()
+			}
+			return nil, err
+		}
+
+	}
+
+	// Doesn't need to be included in the wait group.
+	go db.compactionError()
+	go db.mpoolDrain()
+
+	if readOnly {
+		db.SetReadOnly()
+	} else {
+		db.closeW.Add(2)
+		go db.tCompaction()
+		go db.mCompaction()
+		// go db.jWriter()
+	}
+
+	s.logf("db@open done T·%v", time.Since(start))
+
+	runtime.SetFinalizer(db, (*DB).Close)
+	return db, nil
+}
+
+// Open opens or creates a DB for the given storage.
+// The DB will be created if not exist, unless ErrorIfMissing is true.
+// Also, if ErrorIfExist is true and the DB exist Open will returns
+// os.ErrExist error.
+//
+// Open will return an error with type of ErrCorrupted if corruption
+// detected in the DB. Use errors.IsCorrupted to test whether an error is
+// due to corruption. Corrupted DB can be recovered with Recover function.
+//
+// The returned DB instance is safe for concurrent use.
+// The DB must be closed after use, by calling Close method.
+func Open(stor storage.Storage, o *opt.Options) (db *DB, err error) {
+	s, err := newSession(stor, o)
+	if err != nil {
+		return
+	}
+	defer func() {
+		if err != nil {
+			s.close()
+			s.release()
+		}
+	}()
+
+	err = s.recover()
+	if err != nil {
+		if !os.IsNotExist(err) || s.o.GetErrorIfMissing() || s.o.GetReadOnly() {
+			return
+		}
+		err = s.create()
+		if err != nil {
+			return
+		}
+	} else if s.o.GetErrorIfExist() {
+		err = os.ErrExist
+		return
+	}
+
+	return openDB(s)
+}
+
+// OpenFile opens or creates a DB for the given path.
+// The DB will be created if not exist, unless ErrorIfMissing is true.
+// Also, if ErrorIfExist is true and the DB exist OpenFile will returns
+// os.ErrExist error.
+//
+// OpenFile uses standard file-system backed storage implementation as
+// described in the leveldb/storage package.
+//
+// OpenFile will return an error with type of ErrCorrupted if corruption
+// detected in the DB. Use errors.IsCorrupted to test whether an error is
+// due to corruption. Corrupted DB can be recovered with Recover function.
+//
+// The returned DB instance is safe for concurrent use.
+// The DB must be closed after use, by calling Close method.
+func OpenFile(path string, o *opt.Options) (db *DB, err error) {
+	stor, err := storage.OpenFile(path, o.GetReadOnly())
+	if err != nil {
+		return
+	}
+	db, err = Open(stor, o)
+	if err != nil {
+		stor.Close()
+	} else {
+		db.closer = stor
+	}
+	return
+}
+
+// Recover recovers and opens a DB with missing or corrupted manifest files
+// for the given storage. It will ignore any manifest files, valid or not.
+// The DB must already exist or it will returns an error.
+// Also, Recover will ignore ErrorIfMissing and ErrorIfExist options.
+//
+// The returned DB instance is safe for concurrent use.
+// The DB must be closed after use, by calling Close method.
+func Recover(stor storage.Storage, o *opt.Options) (db *DB, err error) {
+	s, err := newSession(stor, o)
+	if err != nil {
+		return
+	}
+	defer func() {
+		if err != nil {
+			s.close()
+			s.release()
+		}
+	}()
+
+	err = recoverTable(s, o)
+	if err != nil {
+		return
+	}
+	return openDB(s)
+}
+
+// RecoverFile recovers and opens a DB with missing or corrupted manifest files
+// for the given path. It will ignore any manifest files, valid or not.
+// The DB must already exist or it will returns an error.
+// Also, Recover will ignore ErrorIfMissing and ErrorIfExist options.
+//
+// RecoverFile uses standard file-system backed storage implementation as described
+// in the leveldb/storage package.
+//
+// The returned DB instance is safe for concurrent use.
+// The DB must be closed after use, by calling Close method.
+func RecoverFile(path string, o *opt.Options) (db *DB, err error) {
+	stor, err := storage.OpenFile(path, false)
+	if err != nil {
+		return
+	}
+	db, err = Recover(stor, o)
+	if err != nil {
+		stor.Close()
+	} else {
+		db.closer = stor
+	}
+	return
+}
+
+func recoverTable(s *session, o *opt.Options) error {
+	o = dupOptions(o)
+	// Mask StrictReader, lets StrictRecovery doing its job.
+	o.Strict &= ^opt.StrictReader
+
+	// Get all tables and sort it by file number.
+	fds, err := s.stor.List(storage.TypeTable)
+	if err != nil {
+		return err
+	}
+	sortFds(fds)
+
+	var (
+		maxSeq                                                            uint64
+		recoveredKey, goodKey, corruptedKey, corruptedBlock, droppedTable int
+
+		// We will drop corrupted table.
+		strict = o.GetStrict(opt.StrictRecovery)
+		noSync = o.GetNoSync()
+
+		rec   = &sessionRecord{}
+		bpool = util.NewBufferPool(o.GetBlockSize() + 5)
+	)
+	buildTable := func(iter iterator.Iterator) (tmpFd storage.FileDesc, size int64, err error) {
+		tmpFd = s.newTemp()
+		writer, err := s.stor.Create(tmpFd)
+		if err != nil {
+			return
+		}
+		defer func() {
+			writer.Close()
+			if err != nil {
+				s.stor.Remove(tmpFd)
+				tmpFd = storage.FileDesc{}
+			}
+		}()
+
+		// Copy entries.
+		tw := table.NewWriter(writer, o)
+		for iter.Next() {
+			key := iter.Key()
+			if validInternalKey(key) {
+				err = tw.Append(key, iter.Value())
+				if err != nil {
+					return
+				}
+			}
+		}
+		err = iter.Error()
+		if err != nil && !errors.IsCorrupted(err) {
+			return
+		}
+		err = tw.Close()
+		if err != nil {
+			return
+		}
+		if !noSync {
+			err = writer.Sync()
+			if err != nil {
+				return
+			}
+		}
+		size = int64(tw.BytesLen())
+		return
+	}
+	recoverTable := func(fd storage.FileDesc) error {
+		s.logf("table@recovery recovering @%d", fd.Num)
+		reader, err := s.stor.Open(fd)
+		if err != nil {
+			return err
+		}
+		var closed bool
+		defer func() {
+			if !closed {
+				reader.Close()
+			}
+		}()
+
+		// Get file size.
+		size, err := reader.Seek(0, 2)
+		if err != nil {
+			return err
+		}
+
+		var (
+			tSeq                                     uint64
+			tgoodKey, tcorruptedKey, tcorruptedBlock int
+			imin, imax                               []byte
+		)
+		tr, err := table.NewReader(reader, size, fd, nil, bpool, o)
+		if err != nil {
+			return err
+		}
+		iter := tr.NewIterator(nil, nil)
+		if itererr, ok := iter.(iterator.ErrorCallbackSetter); ok {
+			itererr.SetErrorCallback(func(err error) {
+				if errors.IsCorrupted(err) {
+					s.logf("table@recovery block corruption @%d %q", fd.Num, err)
+					tcorruptedBlock++
+				}
+			})
+		}
+
+		// Scan the table.
+		for iter.Next() {
+			key := iter.Key()
+			_, seq, _, kerr := parseInternalKey(key)
+			if kerr != nil {
+				tcorruptedKey++
+				continue
+			}
+			tgoodKey++
+			if seq > tSeq {
+				tSeq = seq
+			}
+			if imin == nil {
+				imin = append([]byte{}, key...)
+			}
+			imax = append(imax[:0], key...)
+		}
+		if err := iter.Error(); err != nil && !errors.IsCorrupted(err) {
+			iter.Release()
+			return err
+		}
+		iter.Release()
+
+		goodKey += tgoodKey
+		corruptedKey += tcorruptedKey
+		corruptedBlock += tcorruptedBlock
+
+		if strict && (tcorruptedKey > 0 || tcorruptedBlock > 0) {
+			droppedTable++
+			s.logf("table@recovery dropped @%d Gk·%d Ck·%d Cb·%d S·%d Q·%d", fd.Num, tgoodKey, tcorruptedKey, tcorruptedBlock, size, tSeq)
+			return nil
+		}
+
+		if tgoodKey > 0 {
+			if tcorruptedKey > 0 || tcorruptedBlock > 0 {
+				// Rebuild the table.
+				s.logf("table@recovery rebuilding @%d", fd.Num)
+				iter := tr.NewIterator(nil, nil)
+				tmpFd, newSize, err := buildTable(iter)
+				iter.Release()
+				if err != nil {
+					return err
+				}
+				closed = true
+				reader.Close()
+				if err := s.stor.Rename(tmpFd, fd); err != nil {
+					return err
+				}
+				size = newSize
+			}
+			if tSeq > maxSeq {
+				maxSeq = tSeq
+			}
+			recoveredKey += tgoodKey
+			// Add table to level 0.
+			rec.addTable(0, fd.Num, size, imin, imax)
+			s.logf("table@recovery recovered @%d Gk·%d Ck·%d Cb·%d S·%d Q·%d", fd.Num, tgoodKey, tcorruptedKey, tcorruptedBlock, size, tSeq)
+		} else {
+			droppedTable++
+			s.logf("table@recovery unrecoverable @%d Ck·%d Cb·%d S·%d", fd.Num, tcorruptedKey, tcorruptedBlock, size)
+		}
+
+		return nil
+	}
+
+	// Recover all tables.
+	if len(fds) > 0 {
+		s.logf("table@recovery F·%d", len(fds))
+
+		// Mark file number as used.
+		s.markFileNum(fds[len(fds)-1].Num)
+
+		for _, fd := range fds {
+			if err := recoverTable(fd); err != nil {
+				return err
+			}
+		}
+
+		s.logf("table@recovery recovered F·%d N·%d Gk·%d Ck·%d Q·%d", len(fds), recoveredKey, goodKey, corruptedKey, maxSeq)
+	}
+
+	// Set sequence number.
+	rec.setSeqNum(maxSeq)
+
+	// Create new manifest.
+	if err := s.create(); err != nil {
+		return err
+	}
+
+	// Commit.
+	return s.commit(rec)
+}
+
+func (db *DB) recoverJournal() error {
+	// Get all journals and sort it by file number.
+	rawFds, err := db.s.stor.List(storage.TypeJournal)
+	if err != nil {
+		return err
+	}
+	sortFds(rawFds)
+
+	// Journals that will be recovered.
+	var fds []storage.FileDesc
+	for _, fd := range rawFds {
+		if fd.Num >= db.s.stJournalNum || fd.Num == db.s.stPrevJournalNum {
+			fds = append(fds, fd)
+		}
+	}
+
+	var (
+		ofd storage.FileDesc // Obsolete file.
+		rec = &sessionRecord{}
+	)
+
+	// Recover journals.
+	if len(fds) > 0 {
+		db.logf("journal@recovery F·%d", len(fds))
+
+		// Mark file number as used.
+		db.s.markFileNum(fds[len(fds)-1].Num)
+
+		var (
+			// Options.
+			strict      = db.s.o.GetStrict(opt.StrictJournal)
+			checksum    = db.s.o.GetStrict(opt.StrictJournalChecksum)
+			writeBuffer = db.s.o.GetWriteBuffer()
+
+			jr       *journal.Reader
+			mdb      = memdb.New(db.s.icmp, writeBuffer)
+			buf      = &util.Buffer{}
+			batchSeq uint64
+			batchLen int
+		)
+
+		for _, fd := range fds {
+			db.logf("journal@recovery recovering @%d", fd.Num)
+
+			fr, err := db.s.stor.Open(fd)
+			if err != nil {
+				return err
+			}
+
+			// Create or reset journal reader instance.
+			if jr == nil {
+				jr = journal.NewReader(fr, dropper{db.s, fd}, strict, checksum)
+			} else {
+				jr.Reset(fr, dropper{db.s, fd}, strict, checksum)
+			}
+
+			// Flush memdb and remove obsolete journal file.
+			if !ofd.Zero() {
+				if mdb.Len() > 0 {
+					if _, err := db.s.flushMemdb(rec, mdb, 0); err != nil {
+						fr.Close()
+						return err
+					}
+				}
+
+				rec.setJournalNum(fd.Num)
+				rec.setSeqNum(db.seq)
+				if err := db.s.commit(rec); err != nil {
+					fr.Close()
+					return err
+				}
+				rec.resetAddedTables()
+
+				db.s.stor.Remove(ofd)
+				ofd = storage.FileDesc{}
+			}
+
+			// Replay journal to memdb.
+			mdb.Reset()
+			for {
+				r, err := jr.Next()
+				if err != nil {
+					if err == io.EOF {
+						break
+					}
+
+					fr.Close()
+					return errors.SetFd(err, fd)
+				}
+
+				buf.Reset()
+				if _, err := buf.ReadFrom(r); err != nil {
+					if err == io.ErrUnexpectedEOF {
+						// This is error returned due to corruption, with strict == false.
+						continue
+					}
+
+					fr.Close()
+					return errors.SetFd(err, fd)
+				}
+				batchSeq, batchLen, err = decodeBatchToMem(buf.Bytes(), db.seq, mdb)
+				if err != nil {
+					if !strict && errors.IsCorrupted(err) {
+						db.s.logf("journal error: %v (skipped)", err)
+						// We won't apply sequence number as it might be corrupted.
+						continue
+					}
+
+					fr.Close()
+					return errors.SetFd(err, fd)
+				}
+
+				// Save sequence number.
+				db.seq = batchSeq + uint64(batchLen)
+
+				// Flush it if large enough.
+				if mdb.Size() >= writeBuffer {
+					if _, err := db.s.flushMemdb(rec, mdb, 0); err != nil {
+						fr.Close()
+						return err
+					}
+
+					mdb.Reset()
+				}
+			}
+
+			fr.Close()
+			ofd = fd
+		}
+
+		// Flush the last memdb.
+		if mdb.Len() > 0 {
+			if _, err := db.s.flushMemdb(rec, mdb, 0); err != nil {
+				return err
+			}
+		}
+	}
+
+	// Create a new journal.
+	if _, err := db.newMem(0); err != nil {
+		return err
+	}
+
+	// Commit.
+	rec.setJournalNum(db.journalFd.Num)
+	rec.setSeqNum(db.seq)
+	if err := db.s.commit(rec); err != nil {
+		// Close journal on error.
+		if db.journal != nil {
+			db.journal.Close()
+			db.journalWriter.Close()
+		}
+		return err
+	}
+
+	// Remove the last obsolete journal file.
+	if !ofd.Zero() {
+		db.s.stor.Remove(ofd)
+	}
+
+	return nil
+}
+
+func (db *DB) recoverJournalRO() error {
+	// Get all journals and sort it by file number.
+	rawFds, err := db.s.stor.List(storage.TypeJournal)
+	if err != nil {
+		return err
+	}
+	sortFds(rawFds)
+
+	// Journals that will be recovered.
+	var fds []storage.FileDesc
+	for _, fd := range rawFds {
+		if fd.Num >= db.s.stJournalNum || fd.Num == db.s.stPrevJournalNum {
+			fds = append(fds, fd)
+		}
+	}
+
+	var (
+		// Options.
+		strict      = db.s.o.GetStrict(opt.StrictJournal)
+		checksum    = db.s.o.GetStrict(opt.StrictJournalChecksum)
+		writeBuffer = db.s.o.GetWriteBuffer()
+
+		mdb = memdb.New(db.s.icmp, writeBuffer)
+	)
+
+	// Recover journals.
+	if len(fds) > 0 {
+		db.logf("journal@recovery RO·Mode F·%d", len(fds))
+
+		var (
+			jr       *journal.Reader
+			buf      = &util.Buffer{}
+			batchSeq uint64
+			batchLen int
+		)
+
+		for _, fd := range fds {
+			db.logf("journal@recovery recovering @%d", fd.Num)
+
+			fr, err := db.s.stor.Open(fd)
+			if err != nil {
+				return err
+			}
+
+			// Create or reset journal reader instance.
+			if jr == nil {
+				jr = journal.NewReader(fr, dropper{db.s, fd}, strict, checksum)
+			} else {
+				jr.Reset(fr, dropper{db.s, fd}, strict, checksum)
+			}
+
+			// Replay journal to memdb.
+			for {
+				r, err := jr.Next()
+				if err != nil {
+					if err == io.EOF {
+						break
+					}
+
+					fr.Close()
+					return errors.SetFd(err, fd)
+				}
+
+				buf.Reset()
+				if _, err := buf.ReadFrom(r); err != nil {
+					if err == io.ErrUnexpectedEOF {
+						// This is error returned due to corruption, with strict == false.
+						continue
+					}
+
+					fr.Close()
+					return errors.SetFd(err, fd)
+				}
+				batchSeq, batchLen, err = decodeBatchToMem(buf.Bytes(), db.seq, mdb)
+				if err != nil {
+					if !strict && errors.IsCorrupted(err) {
+						db.s.logf("journal error: %v (skipped)", err)
+						// We won't apply sequence number as it might be corrupted.
+						continue
+					}
+
+					fr.Close()
+					return errors.SetFd(err, fd)
+				}
+
+				// Save sequence number.
+				db.seq = batchSeq + uint64(batchLen)
+			}
+
+			fr.Close()
+		}
+	}
+
+	// Set memDB.
+	db.mem = &memDB{db: db, DB: mdb, ref: 1}
+
+	return nil
+}
+
+func memGet(mdb *memdb.DB, ikey internalKey, icmp *iComparer) (ok bool, mv []byte, err error) {
+	mk, mv, err := mdb.Find(ikey)
+	if err == nil {
+		ukey, _, kt, kerr := parseInternalKey(mk)
+		if kerr != nil {
+			// Shouldn't have had happen.
+			panic(kerr)
+		}
+		if icmp.uCompare(ukey, ikey.ukey()) == 0 {
+			if kt == keyTypeDel {
+				return true, nil, ErrNotFound
+			}
+			return true, mv, nil
+
+		}
+	} else if err != ErrNotFound {
+		return true, nil, err
+	}
+	return
+}
+
+func (db *DB) get(auxm *memdb.DB, auxt tFiles, key []byte, seq uint64, ro *opt.ReadOptions) (value []byte, err error) {
+	ikey := makeInternalKey(nil, key, seq, keyTypeSeek)
+
+	if auxm != nil {
+		if ok, mv, me := memGet(auxm, ikey, db.s.icmp); ok {
+			return append([]byte{}, mv...), me
+		}
+	}
+
+	em, fm := db.getMems()
+	for _, m := range [...]*memDB{em, fm} {
+		if m == nil {
+			continue
+		}
+		defer m.decref()
+
+		if ok, mv, me := memGet(m.DB, ikey, db.s.icmp); ok {
+			return append([]byte{}, mv...), me
+		}
+	}
+
+	v := db.s.version()
+	value, cSched, err := v.get(auxt, ikey, ro, false)
+	v.release()
+	if cSched {
+		// Trigger table compaction.
+		db.compTrigger(db.tcompCmdC)
+	}
+	return
+}
+
+func nilIfNotFound(err error) error {
+	if err == ErrNotFound {
+		return nil
+	}
+	return err
+}
+
+func (db *DB) has(auxm *memdb.DB, auxt tFiles, key []byte, seq uint64, ro *opt.ReadOptions) (ret bool, err error) {
+	ikey := makeInternalKey(nil, key, seq, keyTypeSeek)
+
+	if auxm != nil {
+		if ok, _, me := memGet(auxm, ikey, db.s.icmp); ok {
+			return me == nil, nilIfNotFound(me)
+		}
+	}
+
+	em, fm := db.getMems()
+	for _, m := range [...]*memDB{em, fm} {
+		if m == nil {
+			continue
+		}
+		defer m.decref()
+
+		if ok, _, me := memGet(m.DB, ikey, db.s.icmp); ok {
+			return me == nil, nilIfNotFound(me)
+		}
+	}
+
+	v := db.s.version()
+	_, cSched, err := v.get(auxt, ikey, ro, true)
+	v.release()
+	if cSched {
+		// Trigger table compaction.
+		db.compTrigger(db.tcompCmdC)
+	}
+	if err == nil {
+		ret = true
+	} else if err == ErrNotFound {
+		err = nil
+	}
+	return
+}
+
+// Get gets the value for the given key. It returns ErrNotFound if the
+// DB does not contains the key.
+//
+// The returned slice is its own copy, it is safe to modify the contents
+// of the returned slice.
+// It is safe to modify the contents of the argument after Get returns.
+func (db *DB) Get(key []byte, ro *opt.ReadOptions) (value []byte, err error) {
+	err = db.ok()
+	if err != nil {
+		return
+	}
+
+	se := db.acquireSnapshot()
+	defer db.releaseSnapshot(se)
+	return db.get(nil, nil, key, se.seq, ro)
+}
+
+// Has returns true if the DB does contains the given key.
+//
+// It is safe to modify the contents of the argument after Has returns.
+func (db *DB) Has(key []byte, ro *opt.ReadOptions) (ret bool, err error) {
+	err = db.ok()
+	if err != nil {
+		return
+	}
+
+	se := db.acquireSnapshot()
+	defer db.releaseSnapshot(se)
+	return db.has(nil, nil, key, se.seq, ro)
+}
+
+// NewIterator returns an iterator for the latest snapshot of the
+// underlying DB.
+// The returned iterator is not safe for concurrent use, but it is safe to use
+// multiple iterators concurrently, with each in a dedicated goroutine.
+// It is also safe to use an iterator concurrently with modifying its
+// underlying DB. The resultant key/value pairs are guaranteed to be
+// consistent.
+//
+// Slice allows slicing the iterator to only contains keys in the given
+// range. A nil Range.Start is treated as a key before all keys in the
+// DB. And a nil Range.Limit is treated as a key after all keys in
+// the DB.
+//
+// WARNING: Any slice returned by interator (e.g. slice returned by calling
+// Iterator.Key() or Iterator.Key() methods), its content should not be modified
+// unless noted otherwise.
+//
+// The iterator must be released after use, by calling Release method.
+//
+// Also read Iterator documentation of the leveldb/iterator package.
+func (db *DB) NewIterator(slice *util.Range, ro *opt.ReadOptions) iterator.Iterator {
+	if err := db.ok(); err != nil {
+		return iterator.NewEmptyIterator(err)
+	}
+
+	se := db.acquireSnapshot()
+	defer db.releaseSnapshot(se)
+	// Iterator holds 'version' lock, 'version' is immutable so snapshot
+	// can be released after iterator created.
+	return db.newIterator(nil, nil, se.seq, slice, ro)
+}
+
+// GetSnapshot returns a latest snapshot of the underlying DB. A snapshot
+// is a frozen snapshot of a DB state at a particular point in time. The
+// content of snapshot are guaranteed to be consistent.
+//
+// The snapshot must be released after use, by calling Release method.
+func (db *DB) GetSnapshot() (*Snapshot, error) {
+	if err := db.ok(); err != nil {
+		return nil, err
+	}
+
+	return db.newSnapshot(), nil
+}
+
+// GetProperty returns value of the given property name.
+//
+// Property names:
+//	leveldb.num-files-at-level{n}
+//		Returns the number of files at level 'n'.
+//	leveldb.stats
+//		Returns statistics of the underlying DB.
+//	leveldb.iostats
+//		Returns statistics of effective disk read and write.
+//	leveldb.writedelay
+//		Returns cumulative write delay caused by compaction.
+//	leveldb.sstables
+//		Returns sstables list for each level.
+//	leveldb.blockpool
+//		Returns block pool stats.
+//	leveldb.cachedblock
+//		Returns size of cached block.
+//	leveldb.openedtables
+//		Returns number of opened tables.
+//	leveldb.alivesnaps
+//		Returns number of alive snapshots.
+//	leveldb.aliveiters
+//		Returns number of alive iterators.
+func (db *DB) GetProperty(name string) (value string, err error) {
+	err = db.ok()
+	if err != nil {
+		return
+	}
+
+	const prefix = "leveldb."
+	if !strings.HasPrefix(name, prefix) {
+		return "", ErrNotFound
+	}
+	p := name[len(prefix):]
+
+	v := db.s.version()
+	defer v.release()
+
+	numFilesPrefix := "num-files-at-level"
+	switch {
+	case strings.HasPrefix(p, numFilesPrefix):
+		var level uint
+		var rest string
+		n, _ := fmt.Sscanf(p[len(numFilesPrefix):], "%d%s", &level, &rest)
+		if n != 1 {
+			err = ErrNotFound
+		} else {
+			value = fmt.Sprint(v.tLen(int(level)))
+		}
+	case p == "stats":
+		value = "Compactions\n" +
+			" Level |   Tables   |    Size(MB)   |    Time(sec)  |    Read(MB)   |   Write(MB)\n" +
+			"-------+------------+---------------+---------------+---------------+---------------\n"
+		for level, tables := range v.levels {
+			duration, read, write := db.compStats.getStat(level)
+			if len(tables) == 0 && duration == 0 {
+				continue
+			}
+			value += fmt.Sprintf(" %3d   | %10d | %13.5f | %13.5f | %13.5f | %13.5f\n",
+				level, len(tables), float64(tables.size())/1048576.0, duration.Seconds(),
+				float64(read)/1048576.0, float64(write)/1048576.0)
+		}
+	case p == "iostats":
+		value = fmt.Sprintf("Read(MB):%.5f Write(MB):%.5f",
+			float64(db.s.stor.reads())/1048576.0,
+			float64(db.s.stor.writes())/1048576.0)
+	case p == "writedelay":
+		writeDelayN, writeDelay := atomic.LoadInt32(&db.cWriteDelayN), time.Duration(atomic.LoadInt64(&db.cWriteDelay))
+		paused := atomic.LoadInt32(&db.inWritePaused) == 1
+		value = fmt.Sprintf("DelayN:%d Delay:%s Paused:%t", writeDelayN, writeDelay, paused)
+	case p == "sstables":
+		for level, tables := range v.levels {
+			value += fmt.Sprintf("--- level %d ---\n", level)
+			for _, t := range tables {
+				value += fmt.Sprintf("%d:%d[%q .. %q]\n", t.fd.Num, t.size, t.imin, t.imax)
+			}
+		}
+	case p == "blockpool":
+		value = fmt.Sprintf("%v", db.s.tops.bpool)
+	case p == "cachedblock":
+		if db.s.tops.bcache != nil {
+			value = fmt.Sprintf("%d", db.s.tops.bcache.Size())
+		} else {
+			value = "<nil>"
+		}
+	case p == "openedtables":
+		value = fmt.Sprintf("%d", db.s.tops.cache.Size())
+	case p == "alivesnaps":
+		value = fmt.Sprintf("%d", atomic.LoadInt32(&db.aliveSnaps))
+	case p == "aliveiters":
+		value = fmt.Sprintf("%d", atomic.LoadInt32(&db.aliveIters))
+	default:
+		err = ErrNotFound
+	}
+
+	return
+}
+
+// DBStats is database statistics.
+type DBStats struct {
+	WriteDelayCount    int32
+	WriteDelayDuration time.Duration
+	WritePaused        bool
+
+	AliveSnapshots int32
+	AliveIterators int32
+
+	IOWrite uint64
+	IORead  uint64
+
+	BlockCacheSize    int
+	OpenedTablesCount int
+
+	LevelSizes        []int64
+	LevelTablesCounts []int
+	LevelRead         []int64
+	LevelWrite        []int64
+	LevelDurations    []time.Duration
+}
+
+// Stats populates s with database statistics.
+func (db *DB) Stats(s *DBStats) error {
+	err := db.ok()
+	if err != nil {
+		return err
+	}
+
+	s.IORead = db.s.stor.reads()
+	s.IOWrite = db.s.stor.writes()
+	s.WriteDelayCount = atomic.LoadInt32(&db.cWriteDelayN)
+	s.WriteDelayDuration = time.Duration(atomic.LoadInt64(&db.cWriteDelay))
+	s.WritePaused = atomic.LoadInt32(&db.inWritePaused) == 1
+
+	s.OpenedTablesCount = db.s.tops.cache.Size()
+	if db.s.tops.bcache != nil {
+		s.BlockCacheSize = db.s.tops.bcache.Size()
+	} else {
+		s.BlockCacheSize = 0
+	}
+
+	s.AliveIterators = atomic.LoadInt32(&db.aliveIters)
+	s.AliveSnapshots = atomic.LoadInt32(&db.aliveSnaps)
+
+	s.LevelDurations = s.LevelDurations[:0]
+	s.LevelRead = s.LevelRead[:0]
+	s.LevelWrite = s.LevelWrite[:0]
+	s.LevelSizes = s.LevelSizes[:0]
+	s.LevelTablesCounts = s.LevelTablesCounts[:0]
+
+	v := db.s.version()
+	defer v.release()
+
+	for level, tables := range v.levels {
+		duration, read, write := db.compStats.getStat(level)
+		if len(tables) == 0 && duration == 0 {
+			continue
+		}
+		s.LevelDurations = append(s.LevelDurations, duration)
+		s.LevelRead = append(s.LevelRead, read)
+		s.LevelWrite = append(s.LevelWrite, write)
+		s.LevelSizes = append(s.LevelSizes, tables.size())
+		s.LevelTablesCounts = append(s.LevelTablesCounts, len(tables))
+	}
+
+	return nil
+}
+
+// SizeOf calculates approximate sizes of the given key ranges.
+// The length of the returned sizes are equal with the length of the given
+// ranges. The returned sizes measure storage space usage, so if the user
+// data compresses by a factor of ten, the returned sizes will be one-tenth
+// the size of the corresponding user data size.
+// The results may not include the sizes of recently written data.
+func (db *DB) SizeOf(ranges []util.Range) (Sizes, error) {
+	if err := db.ok(); err != nil {
+		return nil, err
+	}
+
+	v := db.s.version()
+	defer v.release()
+
+	sizes := make(Sizes, 0, len(ranges))
+	for _, r := range ranges {
+		imin := makeInternalKey(nil, r.Start, keyMaxSeq, keyTypeSeek)
+		imax := makeInternalKey(nil, r.Limit, keyMaxSeq, keyTypeSeek)
+		start, err := v.offsetOf(imin)
+		if err != nil {
+			return nil, err
+		}
+		limit, err := v.offsetOf(imax)
+		if err != nil {
+			return nil, err
+		}
+		var size int64
+		if limit >= start {
+			size = limit - start
+		}
+		sizes = append(sizes, size)
+	}
+
+	return sizes, nil
+}
+
+// Close closes the DB. This will also releases any outstanding snapshot,
+// abort any in-flight compaction and discard open transaction.
+//
+// It is not safe to close a DB until all outstanding iterators are released.
+// It is valid to call Close multiple times. Other methods should not be
+// called after the DB has been closed.
+func (db *DB) Close() error {
+	if !db.setClosed() {
+		return ErrClosed
+	}
+
+	start := time.Now()
+	db.log("db@close closing")
+
+	// Clear the finalizer.
+	runtime.SetFinalizer(db, nil)
+
+	// Get compaction error.
+	var err error
+	select {
+	case err = <-db.compErrC:
+		if err == ErrReadOnly {
+			err = nil
+		}
+	default:
+	}
+
+	// Signal all goroutines.
+	close(db.closeC)
+
+	// Discard open transaction.
+	if db.tr != nil {
+		db.tr.Discard()
+	}
+
+	// Acquire writer lock.
+	db.writeLockC <- struct{}{}
+
+	// Wait for all gorotines to exit.
+	db.closeW.Wait()
+
+	// Closes journal.
+	if db.journal != nil {
+		db.journal.Close()
+		db.journalWriter.Close()
+		db.journal = nil
+		db.journalWriter = nil
+	}
+
+	if db.writeDelayN > 0 {
+		db.logf("db@write was delayed N·%d T·%v", db.writeDelayN, db.writeDelay)
+	}
+
+	// Close session.
+	db.s.close()
+	db.logf("db@close done T·%v", time.Since(start))
+	db.s.release()
+
+	if db.closer != nil {
+		if err1 := db.closer.Close(); err == nil {
+			err = err1
+		}
+		db.closer = nil
+	}
+
+	// Clear memdbs.
+	db.clearMems()
+
+	return err
+}

vendor/github.com/syndtr/goleveldb/leveldb/db_compaction.go

@@ -0,0 +1,854 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"sync"
+	"time"
+
+	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+)
+
+var (
+	errCompactionTransactExiting = errors.New("leveldb: compaction transact exiting")
+)
+
+type cStat struct {
+	duration time.Duration
+	read     int64
+	write    int64
+}
+
+func (p *cStat) add(n *cStatStaging) {
+	p.duration += n.duration
+	p.read += n.read
+	p.write += n.write
+}
+
+func (p *cStat) get() (duration time.Duration, read, write int64) {
+	return p.duration, p.read, p.write
+}
+
+type cStatStaging struct {
+	start    time.Time
+	duration time.Duration
+	on       bool
+	read     int64
+	write    int64
+}
+
+func (p *cStatStaging) startTimer() {
+	if !p.on {
+		p.start = time.Now()
+		p.on = true
+	}
+}
+
+func (p *cStatStaging) stopTimer() {
+	if p.on {
+		p.duration += time.Since(p.start)
+		p.on = false
+	}
+}
+
+type cStats struct {
+	lk    sync.Mutex
+	stats []cStat
+}
+
+func (p *cStats) addStat(level int, n *cStatStaging) {
+	p.lk.Lock()
+	if level >= len(p.stats) {
+		newStats := make([]cStat, level+1)
+		copy(newStats, p.stats)
+		p.stats = newStats
+	}
+	p.stats[level].add(n)
+	p.lk.Unlock()
+}
+
+func (p *cStats) getStat(level int) (duration time.Duration, read, write int64) {
+	p.lk.Lock()
+	defer p.lk.Unlock()
+	if level < len(p.stats) {
+		return p.stats[level].get()
+	}
+	return
+}
+
+func (db *DB) compactionError() {
+	var err error
+noerr:
+	// No error.
+	for {
+		select {
+		case err = <-db.compErrSetC:
+			switch {
+			case err == nil:
+			case err == ErrReadOnly, errors.IsCorrupted(err):
+				goto hasperr
+			default:
+				goto haserr
+			}
+		case <-db.closeC:
+			return
+		}
+	}
+haserr:
+	// Transient error.
+	for {
+		select {
+		case db.compErrC <- err:
+		case err = <-db.compErrSetC:
+			switch {
+			case err == nil:
+				goto noerr
+			case err == ErrReadOnly, errors.IsCorrupted(err):
+				goto hasperr
+			default:
+			}
+		case <-db.closeC:
+			return
+		}
+	}
+hasperr:
+	// Persistent error.
+	for {
+		select {
+		case db.compErrC <- err:
+		case db.compPerErrC <- err:
+		case db.writeLockC <- struct{}{}:
+			// Hold write lock, so that write won't pass-through.
+			db.compWriteLocking = true
+		case <-db.closeC:
+			if db.compWriteLocking {
+				// We should release the lock or Close will hang.
+				<-db.writeLockC
+			}
+			return
+		}
+	}
+}
+
+type compactionTransactCounter int
+
+func (cnt *compactionTransactCounter) incr() {
+	*cnt++
+}
+
+type compactionTransactInterface interface {
+	run(cnt *compactionTransactCounter) error
+	revert() error
+}
+
+func (db *DB) compactionTransact(name string, t compactionTransactInterface) {
+	defer func() {
+		if x := recover(); x != nil {
+			if x == errCompactionTransactExiting {
+				if err := t.revert(); err != nil {
+					db.logf("%s revert error %q", name, err)
+				}
+			}
+			panic(x)
+		}
+	}()
+
+	const (
+		backoffMin = 1 * time.Second
+		backoffMax = 8 * time.Second
+		backoffMul = 2 * time.Second
+	)
+	var (
+		backoff  = backoffMin
+		backoffT = time.NewTimer(backoff)
+		lastCnt  = compactionTransactCounter(0)
+
+		disableBackoff = db.s.o.GetDisableCompactionBackoff()
+	)
+	for n := 0; ; n++ {
+		// Check whether the DB is closed.
+		if db.isClosed() {
+			db.logf("%s exiting", name)
+			db.compactionExitTransact()
+		} else if n > 0 {
+			db.logf("%s retrying N·%d", name, n)
+		}
+
+		// Execute.
+		cnt := compactionTransactCounter(0)
+		err := t.run(&cnt)
+		if err != nil {
+			db.logf("%s error I·%d %q", name, cnt, err)
+		}
+
+		// Set compaction error status.
+		select {
+		case db.compErrSetC <- err:
+		case perr := <-db.compPerErrC:
+			if err != nil {
+				db.logf("%s exiting (persistent error %q)", name, perr)
+				db.compactionExitTransact()
+			}
+		case <-db.closeC:
+			db.logf("%s exiting", name)
+			db.compactionExitTransact()
+		}
+		if err == nil {
+			return
+		}
+		if errors.IsCorrupted(err) {
+			db.logf("%s exiting (corruption detected)", name)
+			db.compactionExitTransact()
+		}
+
+		if !disableBackoff {
+			// Reset backoff duration if counter is advancing.
+			if cnt > lastCnt {
+				backoff = backoffMin
+				lastCnt = cnt
+			}
+
+			// Backoff.
+			backoffT.Reset(backoff)
+			if backoff < backoffMax {
+				backoff *= backoffMul
+				if backoff > backoffMax {
+					backoff = backoffMax
+				}
+			}
+			select {
+			case <-backoffT.C:
+			case <-db.closeC:
+				db.logf("%s exiting", name)
+				db.compactionExitTransact()
+			}
+		}
+	}
+}
+
+type compactionTransactFunc struct {
+	runFunc    func(cnt *compactionTransactCounter) error
+	revertFunc func() error
+}
+
+func (t *compactionTransactFunc) run(cnt *compactionTransactCounter) error {
+	return t.runFunc(cnt)
+}
+
+func (t *compactionTransactFunc) revert() error {
+	if t.revertFunc != nil {
+		return t.revertFunc()
+	}
+	return nil
+}
+
+func (db *DB) compactionTransactFunc(name string, run func(cnt *compactionTransactCounter) error, revert func() error) {
+	db.compactionTransact(name, &compactionTransactFunc{run, revert})
+}
+
+func (db *DB) compactionExitTransact() {
+	panic(errCompactionTransactExiting)
+}
+
+func (db *DB) compactionCommit(name string, rec *sessionRecord) {
+	db.compCommitLk.Lock()
+	defer db.compCommitLk.Unlock() // Defer is necessary.
+	db.compactionTransactFunc(name+"@commit", func(cnt *compactionTransactCounter) error {
+		return db.s.commit(rec)
+	}, nil)
+}
+
+func (db *DB) memCompaction() {
+	mdb := db.getFrozenMem()
+	if mdb == nil {
+		return
+	}
+	defer mdb.decref()
+
+	db.logf("memdb@flush N·%d S·%s", mdb.Len(), shortenb(mdb.Size()))
+
+	// Don't compact empty memdb.
+	if mdb.Len() == 0 {
+		db.logf("memdb@flush skipping")
+		// drop frozen memdb
+		db.dropFrozenMem()
+		return
+	}
+
+	// Pause table compaction.
+	resumeC := make(chan struct{})
+	select {
+	case db.tcompPauseC <- (chan<- struct{})(resumeC):
+	case <-db.compPerErrC:
+		close(resumeC)
+		resumeC = nil
+	case <-db.closeC:
+		db.compactionExitTransact()
+	}
+
+	var (
+		rec        = &sessionRecord{}
+		stats      = &cStatStaging{}
+		flushLevel int
+	)
+
+	// Generate tables.
+	db.compactionTransactFunc("memdb@flush", func(cnt *compactionTransactCounter) (err error) {
+		stats.startTimer()
+		flushLevel, err = db.s.flushMemdb(rec, mdb.DB, db.memdbMaxLevel)
+		stats.stopTimer()
+		return
+	}, func() error {
+		for _, r := range rec.addedTables {
+			db.logf("memdb@flush revert @%d", r.num)
+			if err := db.s.stor.Remove(storage.FileDesc{Type: storage.TypeTable, Num: r.num}); err != nil {
+				return err
+			}
+		}
+		return nil
+	})
+
+	rec.setJournalNum(db.journalFd.Num)
+	rec.setSeqNum(db.frozenSeq)
+
+	// Commit.
+	stats.startTimer()
+	db.compactionCommit("memdb", rec)
+	stats.stopTimer()
+
+	db.logf("memdb@flush committed F·%d T·%v", len(rec.addedTables), stats.duration)
+
+	for _, r := range rec.addedTables {
+		stats.write += r.size
+	}
+	db.compStats.addStat(flushLevel, stats)
+
+	// Drop frozen memdb.
+	db.dropFrozenMem()
+
+	// Resume table compaction.
+	if resumeC != nil {
+		select {
+		case <-resumeC:
+			close(resumeC)
+		case <-db.closeC:
+			db.compactionExitTransact()
+		}
+	}
+
+	// Trigger table compaction.
+	db.compTrigger(db.tcompCmdC)
+}
+
+type tableCompactionBuilder struct {
+	db           *DB
+	s            *session
+	c            *compaction
+	rec          *sessionRecord
+	stat0, stat1 *cStatStaging
+
+	snapHasLastUkey bool
+	snapLastUkey    []byte
+	snapLastSeq     uint64
+	snapIter        int
+	snapKerrCnt     int
+	snapDropCnt     int
+
+	kerrCnt int
+	dropCnt int
+
+	minSeq    uint64
+	strict    bool
+	tableSize int
+
+	tw *tWriter
+}
+
+func (b *tableCompactionBuilder) appendKV(key, value []byte) error {
+	// Create new table if not already.
+	if b.tw == nil {
+		// Check for pause event.
+		if b.db != nil {
+			select {
+			case ch := <-b.db.tcompPauseC:
+				b.db.pauseCompaction(ch)
+			case <-b.db.closeC:
+				b.db.compactionExitTransact()
+			default:
+			}
+		}
+
+		// Create new table.
+		var err error
+		b.tw, err = b.s.tops.create()
+		if err != nil {
+			return err
+		}
+	}
+
+	// Write key/value into table.
+	return b.tw.append(key, value)
+}
+
+func (b *tableCompactionBuilder) needFlush() bool {
+	return b.tw.tw.BytesLen() >= b.tableSize
+}
+
+func (b *tableCompactionBuilder) flush() error {
+	t, err := b.tw.finish()
+	if err != nil {
+		return err
+	}
+	b.rec.addTableFile(b.c.sourceLevel+1, t)
+	b.stat1.write += t.size
+	b.s.logf("table@build created L%d@%d N·%d S·%s %q:%q", b.c.sourceLevel+1, t.fd.Num, b.tw.tw.EntriesLen(), shortenb(int(t.size)), t.imin, t.imax)
+	b.tw = nil
+	return nil
+}
+
+func (b *tableCompactionBuilder) cleanup() {
+	if b.tw != nil {
+		b.tw.drop()
+		b.tw = nil
+	}
+}
+
+func (b *tableCompactionBuilder) run(cnt *compactionTransactCounter) error {
+	snapResumed := b.snapIter > 0
+	hasLastUkey := b.snapHasLastUkey // The key might has zero length, so this is necessary.
+	lastUkey := append([]byte{}, b.snapLastUkey...)
+	lastSeq := b.snapLastSeq
+	b.kerrCnt = b.snapKerrCnt
+	b.dropCnt = b.snapDropCnt
+	// Restore compaction state.
+	b.c.restore()
+
+	defer b.cleanup()
+
+	b.stat1.startTimer()
+	defer b.stat1.stopTimer()
+
+	iter := b.c.newIterator()
+	defer iter.Release()
+	for i := 0; iter.Next(); i++ {
+		// Incr transact counter.
+		cnt.incr()
+
+		// Skip until last state.
+		if i < b.snapIter {
+			continue
+		}
+
+		resumed := false
+		if snapResumed {
+			resumed = true
+			snapResumed = false
+		}
+
+		ikey := iter.Key()
+		ukey, seq, kt, kerr := parseInternalKey(ikey)
+
+		if kerr == nil {
+			shouldStop := !resumed && b.c.shouldStopBefore(ikey)
+
+			if !hasLastUkey || b.s.icmp.uCompare(lastUkey, ukey) != 0 {
+				// First occurrence of this user key.
+
+				// Only rotate tables if ukey doesn't hop across.
+				if b.tw != nil && (shouldStop || b.needFlush()) {
+					if err := b.flush(); err != nil {
+						return err
+					}
+
+					// Creates snapshot of the state.
+					b.c.save()
+					b.snapHasLastUkey = hasLastUkey
+					b.snapLastUkey = append(b.snapLastUkey[:0], lastUkey...)
+					b.snapLastSeq = lastSeq
+					b.snapIter = i
+					b.snapKerrCnt = b.kerrCnt
+					b.snapDropCnt = b.dropCnt
+				}
+
+				hasLastUkey = true
+				lastUkey = append(lastUkey[:0], ukey...)
+				lastSeq = keyMaxSeq
+			}
+
+			switch {
+			case lastSeq <= b.minSeq:
+				// Dropped because newer entry for same user key exist
+				fallthrough // (A)
+			case kt == keyTypeDel && seq <= b.minSeq && b.c.baseLevelForKey(lastUkey):
+				// For this user key:
+				// (1) there is no data in higher levels
+				// (2) data in lower levels will have larger seq numbers
+				// (3) data in layers that are being compacted here and have
+				//     smaller seq numbers will be dropped in the next
+				//     few iterations of this loop (by rule (A) above).
+				// Therefore this deletion marker is obsolete and can be dropped.
+				lastSeq = seq
+				b.dropCnt++
+				continue
+			default:
+				lastSeq = seq
+			}
+		} else {
+			if b.strict {
+				return kerr
+			}
+
+			// Don't drop corrupted keys.
+			hasLastUkey = false
+			lastUkey = lastUkey[:0]
+			lastSeq = keyMaxSeq
+			b.kerrCnt++
+		}
+
+		if err := b.appendKV(ikey, iter.Value()); err != nil {
+			return err
+		}
+	}
+
+	if err := iter.Error(); err != nil {
+		return err
+	}
+
+	// Finish last table.
+	if b.tw != nil && !b.tw.empty() {
+		return b.flush()
+	}
+	return nil
+}
+
+func (b *tableCompactionBuilder) revert() error {
+	for _, at := range b.rec.addedTables {
+		b.s.logf("table@build revert @%d", at.num)
+		if err := b.s.stor.Remove(storage.FileDesc{Type: storage.TypeTable, Num: at.num}); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (db *DB) tableCompaction(c *compaction, noTrivial bool) {
+	defer c.release()
+
+	rec := &sessionRecord{}
+	rec.addCompPtr(c.sourceLevel, c.imax)
+
+	if !noTrivial && c.trivial() {
+		t := c.levels[0][0]
+		db.logf("table@move L%d@%d -> L%d", c.sourceLevel, t.fd.Num, c.sourceLevel+1)
+		rec.delTable(c.sourceLevel, t.fd.Num)
+		rec.addTableFile(c.sourceLevel+1, t)
+		db.compactionCommit("table-move", rec)
+		return
+	}
+
+	var stats [2]cStatStaging
+	for i, tables := range c.levels {
+		for _, t := range tables {
+			stats[i].read += t.size
+			// Insert deleted tables into record
+			rec.delTable(c.sourceLevel+i, t.fd.Num)
+		}
+	}
+	sourceSize := int(stats[0].read + stats[1].read)
+	minSeq := db.minSeq()
+	db.logf("table@compaction L%d·%d -> L%d·%d S·%s Q·%d", c.sourceLevel, len(c.levels[0]), c.sourceLevel+1, len(c.levels[1]), shortenb(sourceSize), minSeq)
+
+	b := &tableCompactionBuilder{
+		db:        db,
+		s:         db.s,
+		c:         c,
+		rec:       rec,
+		stat1:     &stats[1],
+		minSeq:    minSeq,
+		strict:    db.s.o.GetStrict(opt.StrictCompaction),
+		tableSize: db.s.o.GetCompactionTableSize(c.sourceLevel + 1),
+	}
+	db.compactionTransact("table@build", b)
+
+	// Commit.
+	stats[1].startTimer()
+	db.compactionCommit("table", rec)
+	stats[1].stopTimer()
+
+	resultSize := int(stats[1].write)
+	db.logf("table@compaction committed F%s S%s Ke·%d D·%d T·%v", sint(len(rec.addedTables)-len(rec.deletedTables)), sshortenb(resultSize-sourceSize), b.kerrCnt, b.dropCnt, stats[1].duration)
+
+	// Save compaction stats
+	for i := range stats {
+		db.compStats.addStat(c.sourceLevel+1, &stats[i])
+	}
+}
+
+func (db *DB) tableRangeCompaction(level int, umin, umax []byte) error {
+	db.logf("table@compaction range L%d %q:%q", level, umin, umax)
+	if level >= 0 {
+		if c := db.s.getCompactionRange(level, umin, umax, true); c != nil {
+			db.tableCompaction(c, true)
+		}
+	} else {
+		// Retry until nothing to compact.
+		for {
+			compacted := false
+
+			// Scan for maximum level with overlapped tables.
+			v := db.s.version()
+			m := 1
+			for i := m; i < len(v.levels); i++ {
+				tables := v.levels[i]
+				if tables.overlaps(db.s.icmp, umin, umax, false) {
+					m = i
+				}
+			}
+			v.release()
+
+			for level := 0; level < m; level++ {
+				if c := db.s.getCompactionRange(level, umin, umax, false); c != nil {
+					db.tableCompaction(c, true)
+					compacted = true
+				}
+			}
+
+			if !compacted {
+				break
+			}
+		}
+	}
+
+	return nil
+}
+
+func (db *DB) tableAutoCompaction() {
+	if c := db.s.pickCompaction(); c != nil {
+		db.tableCompaction(c, false)
+	}
+}
+
+func (db *DB) tableNeedCompaction() bool {
+	v := db.s.version()
+	defer v.release()
+	return v.needCompaction()
+}
+
+// resumeWrite returns an indicator whether we should resume write operation if enough level0 files are compacted.
+func (db *DB) resumeWrite() bool {
+	v := db.s.version()
+	defer v.release()
+	if v.tLen(0) < db.s.o.GetWriteL0PauseTrigger() {
+		return true
+	}
+	return false
+}
+
+func (db *DB) pauseCompaction(ch chan<- struct{}) {
+	select {
+	case ch <- struct{}{}:
+	case <-db.closeC:
+		db.compactionExitTransact()
+	}
+}
+
+type cCmd interface {
+	ack(err error)
+}
+
+type cAuto struct {
+	// Note for table compaction, an non-empty ackC represents it's a compaction waiting command.
+	ackC chan<- error
+}
+
+func (r cAuto) ack(err error) {
+	if r.ackC != nil {
+		defer func() {
+			recover()
+		}()
+		r.ackC <- err
+	}
+}
+
+type cRange struct {
+	level    int
+	min, max []byte
+	ackC     chan<- error
+}
+
+func (r cRange) ack(err error) {
+	if r.ackC != nil {
+		defer func() {
+			recover()
+		}()
+		r.ackC <- err
+	}
+}
+
+// This will trigger auto compaction but will not wait for it.
+func (db *DB) compTrigger(compC chan<- cCmd) {
+	select {
+	case compC <- cAuto{}:
+	default:
+	}
+}
+
+// This will trigger auto compaction and/or wait for all compaction to be done.
+func (db *DB) compTriggerWait(compC chan<- cCmd) (err error) {
+	ch := make(chan error)
+	defer close(ch)
+	// Send cmd.
+	select {
+	case compC <- cAuto{ch}:
+	case err = <-db.compErrC:
+		return
+	case <-db.closeC:
+		return ErrClosed
+	}
+	// Wait cmd.
+	select {
+	case err = <-ch:
+	case err = <-db.compErrC:
+	case <-db.closeC:
+		return ErrClosed
+	}
+	return err
+}
+
+// Send range compaction request.
+func (db *DB) compTriggerRange(compC chan<- cCmd, level int, min, max []byte) (err error) {
+	ch := make(chan error)
+	defer close(ch)
+	// Send cmd.
+	select {
+	case compC <- cRange{level, min, max, ch}:
+	case err := <-db.compErrC:
+		return err
+	case <-db.closeC:
+		return ErrClosed
+	}
+	// Wait cmd.
+	select {
+	case err = <-ch:
+	case err = <-db.compErrC:
+	case <-db.closeC:
+		return ErrClosed
+	}
+	return err
+}
+
+func (db *DB) mCompaction() {
+	var x cCmd
+
+	defer func() {
+		if x := recover(); x != nil {
+			if x != errCompactionTransactExiting {
+				panic(x)
+			}
+		}
+		if x != nil {
+			x.ack(ErrClosed)
+		}
+		db.closeW.Done()
+	}()
+
+	for {
+		select {
+		case x = <-db.mcompCmdC:
+			switch x.(type) {
+			case cAuto:
+				db.memCompaction()
+				x.ack(nil)
+				x = nil
+			default:
+				panic("leveldb: unknown command")
+			}
+		case <-db.closeC:
+			return
+		}
+	}
+}
+
+func (db *DB) tCompaction() {
+	var (
+		x     cCmd
+		waitQ []cCmd
+	)
+
+	defer func() {
+		if x := recover(); x != nil {
+			if x != errCompactionTransactExiting {
+				panic(x)
+			}
+		}
+		for i := range waitQ {
+			waitQ[i].ack(ErrClosed)
+			waitQ[i] = nil
+		}
+		if x != nil {
+			x.ack(ErrClosed)
+		}
+		db.closeW.Done()
+	}()
+
+	for {
+		if db.tableNeedCompaction() {
+			select {
+			case x = <-db.tcompCmdC:
+			case ch := <-db.tcompPauseC:
+				db.pauseCompaction(ch)
+				continue
+			case <-db.closeC:
+				return
+			default:
+			}
+			// Resume write operation as soon as possible.
+			if len(waitQ) > 0 && db.resumeWrite() {
+				for i := range waitQ {
+					waitQ[i].ack(nil)
+					waitQ[i] = nil
+				}
+				waitQ = waitQ[:0]
+			}
+		} else {
+			for i := range waitQ {
+				waitQ[i].ack(nil)
+				waitQ[i] = nil
+			}
+			waitQ = waitQ[:0]
+			select {
+			case x = <-db.tcompCmdC:
+			case ch := <-db.tcompPauseC:
+				db.pauseCompaction(ch)
+				continue
+			case <-db.closeC:
+				return
+			}
+		}
+		if x != nil {
+			switch cmd := x.(type) {
+			case cAuto:
+				if cmd.ackC != nil {
+					// Check the write pause state before caching it.
+					if db.resumeWrite() {
+						x.ack(nil)
+					} else {
+						waitQ = append(waitQ, x)
+					}
+				}
+			case cRange:
+				x.ack(db.tableRangeCompaction(cmd.level, cmd.min, cmd.max))
+			default:
+				panic("leveldb: unknown command")
+			}
+			x = nil
+		}
+		db.tableAutoCompaction()
+	}
+}

vendor/github.com/syndtr/goleveldb/leveldb/db_iter.go

@@ -0,0 +1,360 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"errors"
+	"math/rand"
+	"runtime"
+	"sync"
+	"sync/atomic"
+
+	"github.com/syndtr/goleveldb/leveldb/iterator"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+var (
+	errInvalidInternalKey = errors.New("leveldb: Iterator: invalid internal key")
+)
+
+type memdbReleaser struct {
+	once sync.Once
+	m    *memDB
+}
+
+func (mr *memdbReleaser) Release() {
+	mr.once.Do(func() {
+		mr.m.decref()
+	})
+}
+
+func (db *DB) newRawIterator(auxm *memDB, auxt tFiles, slice *util.Range, ro *opt.ReadOptions) iterator.Iterator {
+	strict := opt.GetStrict(db.s.o.Options, ro, opt.StrictReader)
+	em, fm := db.getMems()
+	v := db.s.version()
+
+	tableIts := v.getIterators(slice, ro)
+	n := len(tableIts) + len(auxt) + 3
+	its := make([]iterator.Iterator, 0, n)
+
+	if auxm != nil {
+		ami := auxm.NewIterator(slice)
+		ami.SetReleaser(&memdbReleaser{m: auxm})
+		its = append(its, ami)
+	}
+	for _, t := range auxt {
+		its = append(its, v.s.tops.newIterator(t, slice, ro))
+	}
+
+	emi := em.NewIterator(slice)
+	emi.SetReleaser(&memdbReleaser{m: em})
+	its = append(its, emi)
+	if fm != nil {
+		fmi := fm.NewIterator(slice)
+		fmi.SetReleaser(&memdbReleaser{m: fm})
+		its = append(its, fmi)
+	}
+	its = append(its, tableIts...)
+	mi := iterator.NewMergedIterator(its, db.s.icmp, strict)
+	mi.SetReleaser(&versionReleaser{v: v})
+	return mi
+}
+
+func (db *DB) newIterator(auxm *memDB, auxt tFiles, seq uint64, slice *util.Range, ro *opt.ReadOptions) *dbIter {
+	var islice *util.Range
+	if slice != nil {
+		islice = &util.Range{}
+		if slice.Start != nil {
+			islice.Start = makeInternalKey(nil, slice.Start, keyMaxSeq, keyTypeSeek)
+		}
+		if slice.Limit != nil {
+			islice.Limit = makeInternalKey(nil, slice.Limit, keyMaxSeq, keyTypeSeek)
+		}
+	}
+	rawIter := db.newRawIterator(auxm, auxt, islice, ro)
+	iter := &dbIter{
+		db:     db,
+		icmp:   db.s.icmp,
+		iter:   rawIter,
+		seq:    seq,
+		strict: opt.GetStrict(db.s.o.Options, ro, opt.StrictReader),
+		key:    make([]byte, 0),
+		value:  make([]byte, 0),
+	}
+	atomic.AddInt32(&db.aliveIters, 1)
+	runtime.SetFinalizer(iter, (*dbIter).Release)
+	return iter
+}
+
+func (db *DB) iterSamplingRate() int {
+	return rand.Intn(2 * db.s.o.GetIteratorSamplingRate())
+}
+
+type dir int
+
+const (
+	dirReleased dir = iota - 1
+	dirSOI
+	dirEOI
+	dirBackward
+	dirForward
+)
+
+// dbIter represent an interator states over a database session.
+type dbIter struct {
+	db     *DB
+	icmp   *iComparer
+	iter   iterator.Iterator
+	seq    uint64
+	strict bool
+
+	smaplingGap int
+	dir         dir
+	key         []byte
+	value       []byte
+	err         error
+	releaser    util.Releaser
+}
+
+func (i *dbIter) sampleSeek() {
+	ikey := i.iter.Key()
+	i.smaplingGap -= len(ikey) + len(i.iter.Value())
+	for i.smaplingGap < 0 {
+		i.smaplingGap += i.db.iterSamplingRate()
+		i.db.sampleSeek(ikey)
+	}
+}
+
+func (i *dbIter) setErr(err error) {
+	i.err = err
+	i.key = nil
+	i.value = nil
+}
+
+func (i *dbIter) iterErr() {
+	if err := i.iter.Error(); err != nil {
+		i.setErr(err)
+	}
+}
+
+func (i *dbIter) Valid() bool {
+	return i.err == nil && i.dir > dirEOI
+}
+
+func (i *dbIter) First() bool {
+	if i.err != nil {
+		return false
+	} else if i.dir == dirReleased {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	if i.iter.First() {
+		i.dir = dirSOI
+		return i.next()
+	}
+	i.dir = dirEOI
+	i.iterErr()
+	return false
+}
+
+func (i *dbIter) Last() bool {
+	if i.err != nil {
+		return false
+	} else if i.dir == dirReleased {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	if i.iter.Last() {
+		return i.prev()
+	}
+	i.dir = dirSOI
+	i.iterErr()
+	return false
+}
+
+func (i *dbIter) Seek(key []byte) bool {
+	if i.err != nil {
+		return false
+	} else if i.dir == dirReleased {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	ikey := makeInternalKey(nil, key, i.seq, keyTypeSeek)
+	if i.iter.Seek(ikey) {
+		i.dir = dirSOI
+		return i.next()
+	}
+	i.dir = dirEOI
+	i.iterErr()
+	return false
+}
+
+func (i *dbIter) next() bool {
+	for {
+		if ukey, seq, kt, kerr := parseInternalKey(i.iter.Key()); kerr == nil {
+			i.sampleSeek()
+			if seq <= i.seq {
+				switch kt {
+				case keyTypeDel:
+					// Skip deleted key.
+					i.key = append(i.key[:0], ukey...)
+					i.dir = dirForward
+				case keyTypeVal:
+					if i.dir == dirSOI || i.icmp.uCompare(ukey, i.key) > 0 {
+						i.key = append(i.key[:0], ukey...)
+						i.value = append(i.value[:0], i.iter.Value()...)
+						i.dir = dirForward
+						return true
+					}
+				}
+			}
+		} else if i.strict {
+			i.setErr(kerr)
+			break
+		}
+		if !i.iter.Next() {
+			i.dir = dirEOI
+			i.iterErr()
+			break
+		}
+	}
+	return false
+}
+
+func (i *dbIter) Next() bool {
+	if i.dir == dirEOI || i.err != nil {
+		return false
+	} else if i.dir == dirReleased {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	if !i.iter.Next() || (i.dir == dirBackward && !i.iter.Next()) {
+		i.dir = dirEOI
+		i.iterErr()
+		return false
+	}
+	return i.next()
+}
+
+func (i *dbIter) prev() bool {
+	i.dir = dirBackward
+	del := true
+	if i.iter.Valid() {
+		for {
+			if ukey, seq, kt, kerr := parseInternalKey(i.iter.Key()); kerr == nil {
+				i.sampleSeek()
+				if seq <= i.seq {
+					if !del && i.icmp.uCompare(ukey, i.key) < 0 {
+						return true
+					}
+					del = (kt == keyTypeDel)
+					if !del {
+						i.key = append(i.key[:0], ukey...)
+						i.value = append(i.value[:0], i.iter.Value()...)
+					}
+				}
+			} else if i.strict {
+				i.setErr(kerr)
+				return false
+			}
+			if !i.iter.Prev() {
+				break
+			}
+		}
+	}
+	if del {
+		i.dir = dirSOI
+		i.iterErr()
+		return false
+	}
+	return true
+}
+
+func (i *dbIter) Prev() bool {
+	if i.dir == dirSOI || i.err != nil {
+		return false
+	} else if i.dir == dirReleased {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	switch i.dir {
+	case dirEOI:
+		return i.Last()
+	case dirForward:
+		for i.iter.Prev() {
+			if ukey, _, _, kerr := parseInternalKey(i.iter.Key()); kerr == nil {
+				i.sampleSeek()
+				if i.icmp.uCompare(ukey, i.key) < 0 {
+					goto cont
+				}
+			} else if i.strict {
+				i.setErr(kerr)
+				return false
+			}
+		}
+		i.dir = dirSOI
+		i.iterErr()
+		return false
+	}
+
+cont:
+	return i.prev()
+}
+
+func (i *dbIter) Key() []byte {
+	if i.err != nil || i.dir <= dirEOI {
+		return nil
+	}
+	return i.key
+}
+
+func (i *dbIter) Value() []byte {
+	if i.err != nil || i.dir <= dirEOI {
+		return nil
+	}
+	return i.value
+}
+
+func (i *dbIter) Release() {
+	if i.dir != dirReleased {
+		// Clear the finalizer.
+		runtime.SetFinalizer(i, nil)
+
+		if i.releaser != nil {
+			i.releaser.Release()
+			i.releaser = nil
+		}
+
+		i.dir = dirReleased
+		i.key = nil
+		i.value = nil
+		i.iter.Release()
+		i.iter = nil
+		atomic.AddInt32(&i.db.aliveIters, -1)
+		i.db = nil
+	}
+}
+
+func (i *dbIter) SetReleaser(releaser util.Releaser) {
+	if i.dir == dirReleased {
+		panic(util.ErrReleased)
+	}
+	if i.releaser != nil && releaser != nil {
+		panic(util.ErrHasReleaser)
+	}
+	i.releaser = releaser
+}
+
+func (i *dbIter) Error() error {
+	return i.err
+}

vendor/github.com/syndtr/goleveldb/leveldb/db_snapshot.go

@@ -0,0 +1,187 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"container/list"
+	"fmt"
+	"runtime"
+	"sync"
+	"sync/atomic"
+
+	"github.com/syndtr/goleveldb/leveldb/iterator"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+type snapshotElement struct {
+	seq uint64
+	ref int
+	e   *list.Element
+}
+
+// Acquires a snapshot, based on latest sequence.
+func (db *DB) acquireSnapshot() *snapshotElement {
+	db.snapsMu.Lock()
+	defer db.snapsMu.Unlock()
+
+	seq := db.getSeq()
+
+	if e := db.snapsList.Back(); e != nil {
+		se := e.Value.(*snapshotElement)
+		if se.seq == seq {
+			se.ref++
+			return se
+		} else if seq < se.seq {
+			panic("leveldb: sequence number is not increasing")
+		}
+	}
+	se := &snapshotElement{seq: seq, ref: 1}
+	se.e = db.snapsList.PushBack(se)
+	return se
+}
+
+// Releases given snapshot element.
+func (db *DB) releaseSnapshot(se *snapshotElement) {
+	db.snapsMu.Lock()
+	defer db.snapsMu.Unlock()
+
+	se.ref--
+	if se.ref == 0 {
+		db.snapsList.Remove(se.e)
+		se.e = nil
+	} else if se.ref < 0 {
+		panic("leveldb: Snapshot: negative element reference")
+	}
+}
+
+// Gets minimum sequence that not being snapshotted.
+func (db *DB) minSeq() uint64 {
+	db.snapsMu.Lock()
+	defer db.snapsMu.Unlock()
+
+	if e := db.snapsList.Front(); e != nil {
+		return e.Value.(*snapshotElement).seq
+	}
+
+	return db.getSeq()
+}
+
+// Snapshot is a DB snapshot.
+type Snapshot struct {
+	db       *DB
+	elem     *snapshotElement
+	mu       sync.RWMutex
+	released bool
+}
+
+// Creates new snapshot object.
+func (db *DB) newSnapshot() *Snapshot {
+	snap := &Snapshot{
+		db:   db,
+		elem: db.acquireSnapshot(),
+	}
+	atomic.AddInt32(&db.aliveSnaps, 1)
+	runtime.SetFinalizer(snap, (*Snapshot).Release)
+	return snap
+}
+
+func (snap *Snapshot) String() string {
+	return fmt.Sprintf("leveldb.Snapshot{%d}", snap.elem.seq)
+}
+
+// Get gets the value for the given key. It returns ErrNotFound if
+// the DB does not contains the key.
+//
+// The caller should not modify the contents of the returned slice, but
+// it is safe to modify the contents of the argument after Get returns.
+func (snap *Snapshot) Get(key []byte, ro *opt.ReadOptions) (value []byte, err error) {
+	err = snap.db.ok()
+	if err != nil {
+		return
+	}
+	snap.mu.RLock()
+	defer snap.mu.RUnlock()
+	if snap.released {
+		err = ErrSnapshotReleased
+		return
+	}
+	return snap.db.get(nil, nil, key, snap.elem.seq, ro)
+}
+
+// Has returns true if the DB does contains the given key.
+//
+// It is safe to modify the contents of the argument after Get returns.
+func (snap *Snapshot) Has(key []byte, ro *opt.ReadOptions) (ret bool, err error) {
+	err = snap.db.ok()
+	if err != nil {
+		return
+	}
+	snap.mu.RLock()
+	defer snap.mu.RUnlock()
+	if snap.released {
+		err = ErrSnapshotReleased
+		return
+	}
+	return snap.db.has(nil, nil, key, snap.elem.seq, ro)
+}
+
+// NewIterator returns an iterator for the snapshot of the underlying DB.
+// The returned iterator is not safe for concurrent use, but it is safe to use
+// multiple iterators concurrently, with each in a dedicated goroutine.
+// It is also safe to use an iterator concurrently with modifying its
+// underlying DB. The resultant key/value pairs are guaranteed to be
+// consistent.
+//
+// Slice allows slicing the iterator to only contains keys in the given
+// range. A nil Range.Start is treated as a key before all keys in the
+// DB. And a nil Range.Limit is treated as a key after all keys in
+// the DB.
+//
+// WARNING: Any slice returned by interator (e.g. slice returned by calling
+// Iterator.Key() or Iterator.Value() methods), its content should not be
+// modified unless noted otherwise.
+//
+// The iterator must be released after use, by calling Release method.
+// Releasing the snapshot doesn't mean releasing the iterator too, the
+// iterator would be still valid until released.
+//
+// Also read Iterator documentation of the leveldb/iterator package.
+func (snap *Snapshot) NewIterator(slice *util.Range, ro *opt.ReadOptions) iterator.Iterator {
+	if err := snap.db.ok(); err != nil {
+		return iterator.NewEmptyIterator(err)
+	}
+	snap.mu.Lock()
+	defer snap.mu.Unlock()
+	if snap.released {
+		return iterator.NewEmptyIterator(ErrSnapshotReleased)
+	}
+	// Since iterator already hold version ref, it doesn't need to
+	// hold snapshot ref.
+	return snap.db.newIterator(nil, nil, snap.elem.seq, slice, ro)
+}
+
+// Release releases the snapshot. This will not release any returned
+// iterators, the iterators would still be valid until released or the
+// underlying DB is closed.
+//
+// Other methods should not be called after the snapshot has been released.
+func (snap *Snapshot) Release() {
+	snap.mu.Lock()
+	defer snap.mu.Unlock()
+
+	if !snap.released {
+		// Clear the finalizer.
+		runtime.SetFinalizer(snap, nil)
+
+		snap.released = true
+		snap.db.releaseSnapshot(snap.elem)
+		atomic.AddInt32(&snap.db.aliveSnaps, -1)
+		snap.db = nil
+		snap.elem = nil
+	}
+}

vendor/github.com/syndtr/goleveldb/leveldb/db_state.go

@@ -0,0 +1,239 @@
+// Copyright (c) 2013, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"errors"
+	"sync/atomic"
+	"time"
+
+	"github.com/syndtr/goleveldb/leveldb/journal"
+	"github.com/syndtr/goleveldb/leveldb/memdb"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+)
+
+var (
+	errHasFrozenMem = errors.New("has frozen mem")
+)
+
+type memDB struct {
+	db *DB
+	*memdb.DB
+	ref int32
+}
+
+func (m *memDB) getref() int32 {
+	return atomic.LoadInt32(&m.ref)
+}
+
+func (m *memDB) incref() {
+	atomic.AddInt32(&m.ref, 1)
+}
+
+func (m *memDB) decref() {
+	if ref := atomic.AddInt32(&m.ref, -1); ref == 0 {
+		// Only put back memdb with std capacity.
+		if m.Capacity() == m.db.s.o.GetWriteBuffer() {
+			m.Reset()
+			m.db.mpoolPut(m.DB)
+		}
+		m.db = nil
+		m.DB = nil
+	} else if ref < 0 {
+		panic("negative memdb ref")
+	}
+}
+
+// Get latest sequence number.
+func (db *DB) getSeq() uint64 {
+	return atomic.LoadUint64(&db.seq)
+}
+
+// Atomically adds delta to seq.
+func (db *DB) addSeq(delta uint64) {
+	atomic.AddUint64(&db.seq, delta)
+}
+
+func (db *DB) setSeq(seq uint64) {
+	atomic.StoreUint64(&db.seq, seq)
+}
+
+func (db *DB) sampleSeek(ikey internalKey) {
+	v := db.s.version()
+	if v.sampleSeek(ikey) {
+		// Trigger table compaction.
+		db.compTrigger(db.tcompCmdC)
+	}
+	v.release()
+}
+
+func (db *DB) mpoolPut(mem *memdb.DB) {
+	if !db.isClosed() {
+		select {
+		case db.memPool <- mem:
+		default:
+		}
+	}
+}
+
+func (db *DB) mpoolGet(n int) *memDB {
+	var mdb *memdb.DB
+	select {
+	case mdb = <-db.memPool:
+	default:
+	}
+	if mdb == nil || mdb.Capacity() < n {
+		mdb = memdb.New(db.s.icmp, maxInt(db.s.o.GetWriteBuffer(), n))
+	}
+	return &memDB{
+		db: db,
+		DB: mdb,
+	}
+}
+
+func (db *DB) mpoolDrain() {
+	ticker := time.NewTicker(30 * time.Second)
+	for {
+		select {
+		case <-ticker.C:
+			select {
+			case <-db.memPool:
+			default:
+			}
+		case <-db.closeC:
+			ticker.Stop()
+			// Make sure the pool is drained.
+			select {
+			case <-db.memPool:
+			case <-time.After(time.Second):
+			}
+			close(db.memPool)
+			return
+		}
+	}
+}
+
+// Create new memdb and froze the old one; need external synchronization.
+// newMem only called synchronously by the writer.
+func (db *DB) newMem(n int) (mem *memDB, err error) {
+	fd := storage.FileDesc{Type: storage.TypeJournal, Num: db.s.allocFileNum()}
+	w, err := db.s.stor.Create(fd)
+	if err != nil {
+		db.s.reuseFileNum(fd.Num)
+		return
+	}
+
+	db.memMu.Lock()
+	defer db.memMu.Unlock()
+
+	if db.frozenMem != nil {
+		return nil, errHasFrozenMem
+	}
+
+	if db.journal == nil {
+		db.journal = journal.NewWriter(w)
+	} else {
+		db.journal.Reset(w)
+		db.journalWriter.Close()
+		db.frozenJournalFd = db.journalFd
+	}
+	db.journalWriter = w
+	db.journalFd = fd
+	db.frozenMem = db.mem
+	mem = db.mpoolGet(n)
+	mem.incref() // for self
+	mem.incref() // for caller
+	db.mem = mem
+	// The seq only incremented by the writer. And whoever called newMem
+	// should hold write lock, so no need additional synchronization here.
+	db.frozenSeq = db.seq
+	return
+}
+
+// Get all memdbs.
+func (db *DB) getMems() (e, f *memDB) {
+	db.memMu.RLock()
+	defer db.memMu.RUnlock()
+	if db.mem != nil {
+		db.mem.incref()
+	} else if !db.isClosed() {
+		panic("nil effective mem")
+	}
+	if db.frozenMem != nil {
+		db.frozenMem.incref()
+	}
+	return db.mem, db.frozenMem
+}
+
+// Get effective memdb.
+func (db *DB) getEffectiveMem() *memDB {
+	db.memMu.RLock()
+	defer db.memMu.RUnlock()
+	if db.mem != nil {
+		db.mem.incref()
+	} else if !db.isClosed() {
+		panic("nil effective mem")
+	}
+	return db.mem
+}
+
+// Check whether we has frozen memdb.
+func (db *DB) hasFrozenMem() bool {
+	db.memMu.RLock()
+	defer db.memMu.RUnlock()
+	return db.frozenMem != nil
+}
+
+// Get frozen memdb.
+func (db *DB) getFrozenMem() *memDB {
+	db.memMu.RLock()
+	defer db.memMu.RUnlock()
+	if db.frozenMem != nil {
+		db.frozenMem.incref()
+	}
+	return db.frozenMem
+}
+
+// Drop frozen memdb; assume that frozen memdb isn't nil.
+func (db *DB) dropFrozenMem() {
+	db.memMu.Lock()
+	if err := db.s.stor.Remove(db.frozenJournalFd); err != nil {
+		db.logf("journal@remove removing @%d %q", db.frozenJournalFd.Num, err)
+	} else {
+		db.logf("journal@remove removed @%d", db.frozenJournalFd.Num)
+	}
+	db.frozenJournalFd = storage.FileDesc{}
+	db.frozenMem.decref()
+	db.frozenMem = nil
+	db.memMu.Unlock()
+}
+
+// Clear mems ptr; used by DB.Close().
+func (db *DB) clearMems() {
+	db.memMu.Lock()
+	db.mem = nil
+	db.frozenMem = nil
+	db.memMu.Unlock()
+}
+
+// Set closed flag; return true if not already closed.
+func (db *DB) setClosed() bool {
+	return atomic.CompareAndSwapUint32(&db.closed, 0, 1)
+}
+
+// Check whether DB was closed.
+func (db *DB) isClosed() bool {
+	return atomic.LoadUint32(&db.closed) != 0
+}
+
+// Check read ok status.
+func (db *DB) ok() error {
+	if db.isClosed() {
+		return ErrClosed
+	}
+	return nil
+}

vendor/github.com/syndtr/goleveldb/leveldb/db_transaction.go

@@ -0,0 +1,329 @@
+// Copyright (c) 2016, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"errors"
+	"sync"
+	"time"
+
+	"github.com/syndtr/goleveldb/leveldb/iterator"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+var errTransactionDone = errors.New("leveldb: transaction already closed")
+
+// Transaction is the transaction handle.
+type Transaction struct {
+	db        *DB
+	lk        sync.RWMutex
+	seq       uint64
+	mem       *memDB
+	tables    tFiles
+	ikScratch []byte
+	rec       sessionRecord
+	stats     cStatStaging
+	closed    bool
+}
+
+// Get gets the value for the given key. It returns ErrNotFound if the
+// DB does not contains the key.
+//
+// The returned slice is its own copy, it is safe to modify the contents
+// of the returned slice.
+// It is safe to modify the contents of the argument after Get returns.
+func (tr *Transaction) Get(key []byte, ro *opt.ReadOptions) ([]byte, error) {
+	tr.lk.RLock()
+	defer tr.lk.RUnlock()
+	if tr.closed {
+		return nil, errTransactionDone
+	}
+	return tr.db.get(tr.mem.DB, tr.tables, key, tr.seq, ro)
+}
+
+// Has returns true if the DB does contains the given key.
+//
+// It is safe to modify the contents of the argument after Has returns.
+func (tr *Transaction) Has(key []byte, ro *opt.ReadOptions) (bool, error) {
+	tr.lk.RLock()
+	defer tr.lk.RUnlock()
+	if tr.closed {
+		return false, errTransactionDone
+	}
+	return tr.db.has(tr.mem.DB, tr.tables, key, tr.seq, ro)
+}
+
+// NewIterator returns an iterator for the latest snapshot of the transaction.
+// The returned iterator is not safe for concurrent use, but it is safe to use
+// multiple iterators concurrently, with each in a dedicated goroutine.
+// It is also safe to use an iterator concurrently while writes to the
+// transaction. The resultant key/value pairs are guaranteed to be consistent.
+//
+// Slice allows slicing the iterator to only contains keys in the given
+// range. A nil Range.Start is treated as a key before all keys in the
+// DB. And a nil Range.Limit is treated as a key after all keys in
+// the DB.
+//
+// WARNING: Any slice returned by interator (e.g. slice returned by calling
+// Iterator.Key() or Iterator.Key() methods), its content should not be modified
+// unless noted otherwise.
+//
+// The iterator must be released after use, by calling Release method.
+//
+// Also read Iterator documentation of the leveldb/iterator package.
+func (tr *Transaction) NewIterator(slice *util.Range, ro *opt.ReadOptions) iterator.Iterator {
+	tr.lk.RLock()
+	defer tr.lk.RUnlock()
+	if tr.closed {
+		return iterator.NewEmptyIterator(errTransactionDone)
+	}
+	tr.mem.incref()
+	return tr.db.newIterator(tr.mem, tr.tables, tr.seq, slice, ro)
+}
+
+func (tr *Transaction) flush() error {
+	// Flush memdb.
+	if tr.mem.Len() != 0 {
+		tr.stats.startTimer()
+		iter := tr.mem.NewIterator(nil)
+		t, n, err := tr.db.s.tops.createFrom(iter)
+		iter.Release()
+		tr.stats.stopTimer()
+		if err != nil {
+			return err
+		}
+		if tr.mem.getref() == 1 {
+			tr.mem.Reset()
+		} else {
+			tr.mem.decref()
+			tr.mem = tr.db.mpoolGet(0)
+			tr.mem.incref()
+		}
+		tr.tables = append(tr.tables, t)
+		tr.rec.addTableFile(0, t)
+		tr.stats.write += t.size
+		tr.db.logf("transaction@flush created L0@%d N·%d S·%s %q:%q", t.fd.Num, n, shortenb(int(t.size)), t.imin, t.imax)
+	}
+	return nil
+}
+
+func (tr *Transaction) put(kt keyType, key, value []byte) error {
+	tr.ikScratch = makeInternalKey(tr.ikScratch, key, tr.seq+1, kt)
+	if tr.mem.Free() < len(tr.ikScratch)+len(value) {
+		if err := tr.flush(); err != nil {
+			return err
+		}
+	}
+	if err := tr.mem.Put(tr.ikScratch, value); err != nil {
+		return err
+	}
+	tr.seq++
+	return nil
+}
+
+// Put sets the value for the given key. It overwrites any previous value
+// for that key; a DB is not a multi-map.
+// Please note that the transaction is not compacted until committed, so if you
+// writes 10 same keys, then those 10 same keys are in the transaction.
+//
+// It is safe to modify the contents of the arguments after Put returns.
+func (tr *Transaction) Put(key, value []byte, wo *opt.WriteOptions) error {
+	tr.lk.Lock()
+	defer tr.lk.Unlock()
+	if tr.closed {
+		return errTransactionDone
+	}
+	return tr.put(keyTypeVal, key, value)
+}
+
+// Delete deletes the value for the given key.
+// Please note that the transaction is not compacted until committed, so if you
+// writes 10 same keys, then those 10 same keys are in the transaction.
+//
+// It is safe to modify the contents of the arguments after Delete returns.
+func (tr *Transaction) Delete(key []byte, wo *opt.WriteOptions) error {
+	tr.lk.Lock()
+	defer tr.lk.Unlock()
+	if tr.closed {
+		return errTransactionDone
+	}
+	return tr.put(keyTypeDel, key, nil)
+}
+
+// Write apply the given batch to the transaction. The batch will be applied
+// sequentially.
+// Please note that the transaction is not compacted until committed, so if you
+// writes 10 same keys, then those 10 same keys are in the transaction.
+//
+// It is safe to modify the contents of the arguments after Write returns.
+func (tr *Transaction) Write(b *Batch, wo *opt.WriteOptions) error {
+	if b == nil || b.Len() == 0 {
+		return nil
+	}
+
+	tr.lk.Lock()
+	defer tr.lk.Unlock()
+	if tr.closed {
+		return errTransactionDone
+	}
+	return b.replayInternal(func(i int, kt keyType, k, v []byte) error {
+		return tr.put(kt, k, v)
+	})
+}
+
+func (tr *Transaction) setDone() {
+	tr.closed = true
+	tr.db.tr = nil
+	tr.mem.decref()
+	<-tr.db.writeLockC
+}
+
+// Commit commits the transaction. If error is not nil, then the transaction is
+// not committed, it can then either be retried or discarded.
+//
+// Other methods should not be called after transaction has been committed.
+func (tr *Transaction) Commit() error {
+	if err := tr.db.ok(); err != nil {
+		return err
+	}
+
+	tr.lk.Lock()
+	defer tr.lk.Unlock()
+	if tr.closed {
+		return errTransactionDone
+	}
+	if err := tr.flush(); err != nil {
+		// Return error, lets user decide either to retry or discard
+		// transaction.
+		return err
+	}
+	if len(tr.tables) != 0 {
+		// Committing transaction.
+		tr.rec.setSeqNum(tr.seq)
+		tr.db.compCommitLk.Lock()
+		tr.stats.startTimer()
+		var cerr error
+		for retry := 0; retry < 3; retry++ {
+			cerr = tr.db.s.commit(&tr.rec)
+			if cerr != nil {
+				tr.db.logf("transaction@commit error R·%d %q", retry, cerr)
+				select {
+				case <-time.After(time.Second):
+				case <-tr.db.closeC:
+					tr.db.logf("transaction@commit exiting")
+					tr.db.compCommitLk.Unlock()
+					return cerr
+				}
+			} else {
+				// Success. Set db.seq.
+				tr.db.setSeq(tr.seq)
+				break
+			}
+		}
+		tr.stats.stopTimer()
+		if cerr != nil {
+			// Return error, lets user decide either to retry or discard
+			// transaction.
+			return cerr
+		}
+
+		// Update compaction stats. This is safe as long as we hold compCommitLk.
+		tr.db.compStats.addStat(0, &tr.stats)
+
+		// Trigger table auto-compaction.
+		tr.db.compTrigger(tr.db.tcompCmdC)
+		tr.db.compCommitLk.Unlock()
+
+		// Additionally, wait compaction when certain threshold reached.
+		// Ignore error, returns error only if transaction can't be committed.
+		tr.db.waitCompaction()
+	}
+	// Only mark as done if transaction committed successfully.
+	tr.setDone()
+	return nil
+}
+
+func (tr *Transaction) discard() {
+	// Discard transaction.
+	for _, t := range tr.tables {
+		tr.db.logf("transaction@discard @%d", t.fd.Num)
+		if err1 := tr.db.s.stor.Remove(t.fd); err1 == nil {
+			tr.db.s.reuseFileNum(t.fd.Num)
+		}
+	}
+}
+
+// Discard discards the transaction.
+//
+// Other methods should not be called after transaction has been discarded.
+func (tr *Transaction) Discard() {
+	tr.lk.Lock()
+	if !tr.closed {
+		tr.discard()
+		tr.setDone()
+	}
+	tr.lk.Unlock()
+}
+
+func (db *DB) waitCompaction() error {
+	if db.s.tLen(0) >= db.s.o.GetWriteL0PauseTrigger() {
+		return db.compTriggerWait(db.tcompCmdC)
+	}
+	return nil
+}
+
+// OpenTransaction opens an atomic DB transaction. Only one transaction can be
+// opened at a time. Subsequent call to Write and OpenTransaction will be blocked
+// until in-flight transaction is committed or discarded.
+// The returned transaction handle is safe for concurrent use.
+//
+// Transaction is expensive and can overwhelm compaction, especially if
+// transaction size is small. Use with caution.
+//
+// The transaction must be closed once done, either by committing or discarding
+// the transaction.
+// Closing the DB will discard open transaction.
+func (db *DB) OpenTransaction() (*Transaction, error) {
+	if err := db.ok(); err != nil {
+		return nil, err
+	}
+
+	// The write happen synchronously.
+	select {
+	case db.writeLockC <- struct{}{}:
+	case err := <-db.compPerErrC:
+		return nil, err
+	case <-db.closeC:
+		return nil, ErrClosed
+	}
+
+	if db.tr != nil {
+		panic("leveldb: has open transaction")
+	}
+
+	// Flush current memdb.
+	if db.mem != nil && db.mem.Len() != 0 {
+		if _, err := db.rotateMem(0, true); err != nil {
+			return nil, err
+		}
+	}
+
+	// Wait compaction when certain threshold reached.
+	if err := db.waitCompaction(); err != nil {
+		return nil, err
+	}
+
+	tr := &Transaction{
+		db:  db,
+		seq: db.seq,
+		mem: db.mpoolGet(0),
+	}
+	tr.mem.incref()
+	db.tr = tr
+	return tr, nil
+}

vendor/github.com/syndtr/goleveldb/leveldb/db_util.go

@@ -0,0 +1,102 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/iterator"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+// Reader is the interface that wraps basic Get and NewIterator methods.
+// This interface implemented by both DB and Snapshot.
+type Reader interface {
+	Get(key []byte, ro *opt.ReadOptions) (value []byte, err error)
+	NewIterator(slice *util.Range, ro *opt.ReadOptions) iterator.Iterator
+}
+
+// Sizes is list of size.
+type Sizes []int64
+
+// Sum returns sum of the sizes.
+func (sizes Sizes) Sum() int64 {
+	var sum int64
+	for _, size := range sizes {
+		sum += size
+	}
+	return sum
+}
+
+// Logging.
+func (db *DB) log(v ...interface{})                 { db.s.log(v...) }
+func (db *DB) logf(format string, v ...interface{}) { db.s.logf(format, v...) }
+
+// Check and clean files.
+func (db *DB) checkAndCleanFiles() error {
+	v := db.s.version()
+	defer v.release()
+
+	tmap := make(map[int64]bool)
+	for _, tables := range v.levels {
+		for _, t := range tables {
+			tmap[t.fd.Num] = false
+		}
+	}
+
+	fds, err := db.s.stor.List(storage.TypeAll)
+	if err != nil {
+		return err
+	}
+
+	var nt int
+	var rem []storage.FileDesc
+	for _, fd := range fds {
+		keep := true
+		switch fd.Type {
+		case storage.TypeManifest:
+			keep = fd.Num >= db.s.manifestFd.Num
+		case storage.TypeJournal:
+			if !db.frozenJournalFd.Zero() {
+				keep = fd.Num >= db.frozenJournalFd.Num
+			} else {
+				keep = fd.Num >= db.journalFd.Num
+			}
+		case storage.TypeTable:
+			_, keep = tmap[fd.Num]
+			if keep {
+				tmap[fd.Num] = true
+				nt++
+			}
+		}
+
+		if !keep {
+			rem = append(rem, fd)
+		}
+	}
+
+	if nt != len(tmap) {
+		var mfds []storage.FileDesc
+		for num, present := range tmap {
+			if !present {
+				mfds = append(mfds, storage.FileDesc{Type: storage.TypeTable, Num: num})
+				db.logf("db@janitor table missing @%d", num)
+			}
+		}
+		return errors.NewErrCorrupted(storage.FileDesc{}, &errors.ErrMissingFiles{Fds: mfds})
+	}
+
+	db.logf("db@janitor F·%d G·%d", len(fds), len(rem))
+	for _, fd := range rem {
+		db.logf("db@janitor removing %s-%d", fd.Type, fd.Num)
+		if err := db.s.stor.Remove(fd); err != nil {
+			return err
+		}
+	}
+	return nil
+}

vendor/github.com/syndtr/goleveldb/leveldb/db_write.go

@@ -0,0 +1,464 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"sync/atomic"
+	"time"
+
+	"github.com/syndtr/goleveldb/leveldb/memdb"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+func (db *DB) writeJournal(batches []*Batch, seq uint64, sync bool) error {
+	wr, err := db.journal.Next()
+	if err != nil {
+		return err
+	}
+	if err := writeBatchesWithHeader(wr, batches, seq); err != nil {
+		return err
+	}
+	if err := db.journal.Flush(); err != nil {
+		return err
+	}
+	if sync {
+		return db.journalWriter.Sync()
+	}
+	return nil
+}
+
+func (db *DB) rotateMem(n int, wait bool) (mem *memDB, err error) {
+	retryLimit := 3
+retry:
+	// Wait for pending memdb compaction.
+	err = db.compTriggerWait(db.mcompCmdC)
+	if err != nil {
+		return
+	}
+	retryLimit--
+
+	// Create new memdb and journal.
+	mem, err = db.newMem(n)
+	if err != nil {
+		if err == errHasFrozenMem {
+			if retryLimit <= 0 {
+				panic("BUG: still has frozen memdb")
+			}
+			goto retry
+		}
+		return
+	}
+
+	// Schedule memdb compaction.
+	if wait {
+		err = db.compTriggerWait(db.mcompCmdC)
+	} else {
+		db.compTrigger(db.mcompCmdC)
+	}
+	return
+}
+
+func (db *DB) flush(n int) (mdb *memDB, mdbFree int, err error) {
+	delayed := false
+	slowdownTrigger := db.s.o.GetWriteL0SlowdownTrigger()
+	pauseTrigger := db.s.o.GetWriteL0PauseTrigger()
+	flush := func() (retry bool) {
+		mdb = db.getEffectiveMem()
+		if mdb == nil {
+			err = ErrClosed
+			return false
+		}
+		defer func() {
+			if retry {
+				mdb.decref()
+				mdb = nil
+			}
+		}()
+		tLen := db.s.tLen(0)
+		mdbFree = mdb.Free()
+		switch {
+		case tLen >= slowdownTrigger && !delayed:
+			delayed = true
+			time.Sleep(time.Millisecond)
+		case mdbFree >= n:
+			return false
+		case tLen >= pauseTrigger:
+			delayed = true
+			// Set the write paused flag explicitly.
+			atomic.StoreInt32(&db.inWritePaused, 1)
+			err = db.compTriggerWait(db.tcompCmdC)
+			// Unset the write paused flag.
+			atomic.StoreInt32(&db.inWritePaused, 0)
+			if err != nil {
+				return false
+			}
+		default:
+			// Allow memdb to grow if it has no entry.
+			if mdb.Len() == 0 {
+				mdbFree = n
+			} else {
+				mdb.decref()
+				mdb, err = db.rotateMem(n, false)
+				if err == nil {
+					mdbFree = mdb.Free()
+				} else {
+					mdbFree = 0
+				}
+			}
+			return false
+		}
+		return true
+	}
+	start := time.Now()
+	for flush() {
+	}
+	if delayed {
+		db.writeDelay += time.Since(start)
+		db.writeDelayN++
+	} else if db.writeDelayN > 0 {
+		db.logf("db@write was delayed N·%d T·%v", db.writeDelayN, db.writeDelay)
+		atomic.AddInt32(&db.cWriteDelayN, int32(db.writeDelayN))
+		atomic.AddInt64(&db.cWriteDelay, int64(db.writeDelay))
+		db.writeDelay = 0
+		db.writeDelayN = 0
+	}
+	return
+}
+
+type writeMerge struct {
+	sync       bool
+	batch      *Batch
+	keyType    keyType
+	key, value []byte
+}
+
+func (db *DB) unlockWrite(overflow bool, merged int, err error) {
+	for i := 0; i < merged; i++ {
+		db.writeAckC <- err
+	}
+	if overflow {
+		// Pass lock to the next write (that failed to merge).
+		db.writeMergedC <- false
+	} else {
+		// Release lock.
+		<-db.writeLockC
+	}
+}
+
+// ourBatch is batch that we can modify.
+func (db *DB) writeLocked(batch, ourBatch *Batch, merge, sync bool) error {
+	// Try to flush memdb. This method would also trying to throttle writes
+	// if it is too fast and compaction cannot catch-up.
+	mdb, mdbFree, err := db.flush(batch.internalLen)
+	if err != nil {
+		db.unlockWrite(false, 0, err)
+		return err
+	}
+	defer mdb.decref()
+
+	var (
+		overflow bool
+		merged   int
+		batches  = []*Batch{batch}
+	)
+
+	if merge {
+		// Merge limit.
+		var mergeLimit int
+		if batch.internalLen > 128<<10 {
+			mergeLimit = (1 << 20) - batch.internalLen
+		} else {
+			mergeLimit = 128 << 10
+		}
+		mergeCap := mdbFree - batch.internalLen
+		if mergeLimit > mergeCap {
+			mergeLimit = mergeCap
+		}
+
+	merge:
+		for mergeLimit > 0 {
+			select {
+			case incoming := <-db.writeMergeC:
+				if incoming.batch != nil {
+					// Merge batch.
+					if incoming.batch.internalLen > mergeLimit {
+						overflow = true
+						break merge
+					}
+					batches = append(batches, incoming.batch)
+					mergeLimit -= incoming.batch.internalLen
+				} else {
+					// Merge put.
+					internalLen := len(incoming.key) + len(incoming.value) + 8
+					if internalLen > mergeLimit {
+						overflow = true
+						break merge
+					}
+					if ourBatch == nil {
+						ourBatch = db.batchPool.Get().(*Batch)
+						ourBatch.Reset()
+						batches = append(batches, ourBatch)
+					}
+					// We can use same batch since concurrent write doesn't
+					// guarantee write order.
+					ourBatch.appendRec(incoming.keyType, incoming.key, incoming.value)
+					mergeLimit -= internalLen
+				}
+				sync = sync || incoming.sync
+				merged++
+				db.writeMergedC <- true
+
+			default:
+				break merge
+			}
+		}
+	}
+
+	// Release ourBatch if any.
+	if ourBatch != nil {
+		defer db.batchPool.Put(ourBatch)
+	}
+
+	// Seq number.
+	seq := db.seq + 1
+
+	// Write journal.
+	if err := db.writeJournal(batches, seq, sync); err != nil {
+		db.unlockWrite(overflow, merged, err)
+		return err
+	}
+
+	// Put batches.
+	for _, batch := range batches {
+		if err := batch.putMem(seq, mdb.DB); err != nil {
+			panic(err)
+		}
+		seq += uint64(batch.Len())
+	}
+
+	// Incr seq number.
+	db.addSeq(uint64(batchesLen(batches)))
+
+	// Rotate memdb if it's reach the threshold.
+	if batch.internalLen >= mdbFree {
+		db.rotateMem(0, false)
+	}
+
+	db.unlockWrite(overflow, merged, nil)
+	return nil
+}
+
+// Write apply the given batch to the DB. The batch records will be applied
+// sequentially. Write might be used concurrently, when used concurrently and
+// batch is small enough, write will try to merge the batches. Set NoWriteMerge
+// option to true to disable write merge.
+//
+// It is safe to modify the contents of the arguments after Write returns but
+// not before. Write will not modify content of the batch.
+func (db *DB) Write(batch *Batch, wo *opt.WriteOptions) error {
+	if err := db.ok(); err != nil || batch == nil || batch.Len() == 0 {
+		return err
+	}
+
+	// If the batch size is larger than write buffer, it may justified to write
+	// using transaction instead. Using transaction the batch will be written
+	// into tables directly, skipping the journaling.
+	if batch.internalLen > db.s.o.GetWriteBuffer() && !db.s.o.GetDisableLargeBatchTransaction() {
+		tr, err := db.OpenTransaction()
+		if err != nil {
+			return err
+		}
+		if err := tr.Write(batch, wo); err != nil {
+			tr.Discard()
+			return err
+		}
+		return tr.Commit()
+	}
+
+	merge := !wo.GetNoWriteMerge() && !db.s.o.GetNoWriteMerge()
+	sync := wo.GetSync() && !db.s.o.GetNoSync()
+
+	// Acquire write lock.
+	if merge {
+		select {
+		case db.writeMergeC <- writeMerge{sync: sync, batch: batch}:
+			if <-db.writeMergedC {
+				// Write is merged.
+				return <-db.writeAckC
+			}
+			// Write is not merged, the write lock is handed to us. Continue.
+		case db.writeLockC <- struct{}{}:
+			// Write lock acquired.
+		case err := <-db.compPerErrC:
+			// Compaction error.
+			return err
+		case <-db.closeC:
+			// Closed
+			return ErrClosed
+		}
+	} else {
+		select {
+		case db.writeLockC <- struct{}{}:
+			// Write lock acquired.
+		case err := <-db.compPerErrC:
+			// Compaction error.
+			return err
+		case <-db.closeC:
+			// Closed
+			return ErrClosed
+		}
+	}
+
+	return db.writeLocked(batch, nil, merge, sync)
+}
+
+func (db *DB) putRec(kt keyType, key, value []byte, wo *opt.WriteOptions) error {
+	if err := db.ok(); err != nil {
+		return err
+	}
+
+	merge := !wo.GetNoWriteMerge() && !db.s.o.GetNoWriteMerge()
+	sync := wo.GetSync() && !db.s.o.GetNoSync()
+
+	// Acquire write lock.
+	if merge {
+		select {
+		case db.writeMergeC <- writeMerge{sync: sync, keyType: kt, key: key, value: value}:
+			if <-db.writeMergedC {
+				// Write is merged.
+				return <-db.writeAckC
+			}
+			// Write is not merged, the write lock is handed to us. Continue.
+		case db.writeLockC <- struct{}{}:
+			// Write lock acquired.
+		case err := <-db.compPerErrC:
+			// Compaction error.
+			return err
+		case <-db.closeC:
+			// Closed
+			return ErrClosed
+		}
+	} else {
+		select {
+		case db.writeLockC <- struct{}{}:
+			// Write lock acquired.
+		case err := <-db.compPerErrC:
+			// Compaction error.
+			return err
+		case <-db.closeC:
+			// Closed
+			return ErrClosed
+		}
+	}
+
+	batch := db.batchPool.Get().(*Batch)
+	batch.Reset()
+	batch.appendRec(kt, key, value)
+	return db.writeLocked(batch, batch, merge, sync)
+}
+
+// Put sets the value for the given key. It overwrites any previous value
+// for that key; a DB is not a multi-map. Write merge also applies for Put, see
+// Write.
+//
+// It is safe to modify the contents of the arguments after Put returns but not
+// before.
+func (db *DB) Put(key, value []byte, wo *opt.WriteOptions) error {
+	return db.putRec(keyTypeVal, key, value, wo)
+}
+
+// Delete deletes the value for the given key. Delete will not returns error if
+// key doesn't exist. Write merge also applies for Delete, see Write.
+//
+// It is safe to modify the contents of the arguments after Delete returns but
+// not before.
+func (db *DB) Delete(key []byte, wo *opt.WriteOptions) error {
+	return db.putRec(keyTypeDel, key, nil, wo)
+}
+
+func isMemOverlaps(icmp *iComparer, mem *memdb.DB, min, max []byte) bool {
+	iter := mem.NewIterator(nil)
+	defer iter.Release()
+	return (max == nil || (iter.First() && icmp.uCompare(max, internalKey(iter.Key()).ukey()) >= 0)) &&
+		(min == nil || (iter.Last() && icmp.uCompare(min, internalKey(iter.Key()).ukey()) <= 0))
+}
+
+// CompactRange compacts the underlying DB for the given key range.
+// In particular, deleted and overwritten versions are discarded,
+// and the data is rearranged to reduce the cost of operations
+// needed to access the data. This operation should typically only
+// be invoked by users who understand the underlying implementation.
+//
+// A nil Range.Start is treated as a key before all keys in the DB.
+// And a nil Range.Limit is treated as a key after all keys in the DB.
+// Therefore if both is nil then it will compact entire DB.
+func (db *DB) CompactRange(r util.Range) error {
+	if err := db.ok(); err != nil {
+		return err
+	}
+
+	// Lock writer.
+	select {
+	case db.writeLockC <- struct{}{}:
+	case err := <-db.compPerErrC:
+		return err
+	case <-db.closeC:
+		return ErrClosed
+	}
+
+	// Check for overlaps in memdb.
+	mdb := db.getEffectiveMem()
+	if mdb == nil {
+		return ErrClosed
+	}
+	defer mdb.decref()
+	if isMemOverlaps(db.s.icmp, mdb.DB, r.Start, r.Limit) {
+		// Memdb compaction.
+		if _, err := db.rotateMem(0, false); err != nil {
+			<-db.writeLockC
+			return err
+		}
+		<-db.writeLockC
+		if err := db.compTriggerWait(db.mcompCmdC); err != nil {
+			return err
+		}
+	} else {
+		<-db.writeLockC
+	}
+
+	// Table compaction.
+	return db.compTriggerRange(db.tcompCmdC, -1, r.Start, r.Limit)
+}
+
+// SetReadOnly makes DB read-only. It will stay read-only until reopened.
+func (db *DB) SetReadOnly() error {
+	if err := db.ok(); err != nil {
+		return err
+	}
+
+	// Lock writer.
+	select {
+	case db.writeLockC <- struct{}{}:
+		db.compWriteLocking = true
+	case err := <-db.compPerErrC:
+		return err
+	case <-db.closeC:
+		return ErrClosed
+	}
+
+	// Set compaction read-only.
+	select {
+	case db.compErrSetC <- ErrReadOnly:
+	case perr := <-db.compPerErrC:
+		return perr
+	case <-db.closeC:
+		return ErrClosed
+	}
+
+	return nil
+}

vendor/github.com/syndtr/goleveldb/leveldb/doc.go

@@ -0,0 +1,92 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Package leveldb provides implementation of LevelDB key/value database.
+//
+// Create or open a database:
+//
+//	// The returned DB instance is safe for concurrent use. Which mean that all
+//	// DB's methods may be called concurrently from multiple goroutine.
+//	db, err := leveldb.OpenFile("path/to/db", nil)
+//	...
+//	defer db.Close()
+//	...
+//
+// Read or modify the database content:
+//
+//	// Remember that the contents of the returned slice should not be modified.
+//	data, err := db.Get([]byte("key"), nil)
+//	...
+//	err = db.Put([]byte("key"), []byte("value"), nil)
+//	...
+//	err = db.Delete([]byte("key"), nil)
+//	...
+//
+// Iterate over database content:
+//
+//	iter := db.NewIterator(nil, nil)
+//	for iter.Next() {
+//		// Remember that the contents of the returned slice should not be modified, and
+//		// only valid until the next call to Next.
+//		key := iter.Key()
+//		value := iter.Value()
+//		...
+//	}
+//	iter.Release()
+//	err = iter.Error()
+//	...
+//
+// Iterate over subset of database content with a particular prefix:
+//	iter := db.NewIterator(util.BytesPrefix([]byte("foo-")), nil)
+//	for iter.Next() {
+//		// Use key/value.
+//		...
+//	}
+//	iter.Release()
+//	err = iter.Error()
+//	...
+//
+// Seek-then-Iterate:
+//
+// 	iter := db.NewIterator(nil, nil)
+// 	for ok := iter.Seek(key); ok; ok = iter.Next() {
+// 		// Use key/value.
+// 		...
+// 	}
+// 	iter.Release()
+// 	err = iter.Error()
+// 	...
+//
+// Iterate over subset of database content:
+//
+// 	iter := db.NewIterator(&util.Range{Start: []byte("foo"), Limit: []byte("xoo")}, nil)
+// 	for iter.Next() {
+// 		// Use key/value.
+// 		...
+// 	}
+// 	iter.Release()
+// 	err = iter.Error()
+// 	...
+//
+// Batch writes:
+//
+//	batch := new(leveldb.Batch)
+//	batch.Put([]byte("foo"), []byte("value"))
+//	batch.Put([]byte("bar"), []byte("another value"))
+//	batch.Delete([]byte("baz"))
+//	err = db.Write(batch, nil)
+//	...
+//
+// Use bloom filter:
+//
+//	o := &opt.Options{
+//		Filter: filter.NewBloomFilter(10),
+//	}
+//	db, err := leveldb.OpenFile("path/to/db", o)
+//	...
+//	defer db.Close()
+//	...
+package leveldb

vendor/github.com/syndtr/goleveldb/leveldb/errors.go

@@ -0,0 +1,20 @@
+// Copyright (c) 2014, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"github.com/syndtr/goleveldb/leveldb/errors"
+)
+
+// Common errors.
+var (
+	ErrNotFound         = errors.ErrNotFound
+	ErrReadOnly         = errors.New("leveldb: read-only mode")
+	ErrSnapshotReleased = errors.New("leveldb: snapshot released")
+	ErrIterReleased     = errors.New("leveldb: iterator released")
+	ErrClosed           = errors.New("leveldb: closed")
+)

vendor/github.com/syndtr/goleveldb/leveldb/errors/errors.go

@@ -0,0 +1,78 @@
+// Copyright (c) 2014, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Package errors provides common error types used throughout leveldb.
+package errors
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/syndtr/goleveldb/leveldb/storage"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+// Common errors.
+var (
+	ErrNotFound    = New("leveldb: not found")
+	ErrReleased    = util.ErrReleased
+	ErrHasReleaser = util.ErrHasReleaser
+)
+
+// New returns an error that formats as the given text.
+func New(text string) error {
+	return errors.New(text)
+}
+
+// ErrCorrupted is the type that wraps errors that indicate corruption in
+// the database.
+type ErrCorrupted struct {
+	Fd  storage.FileDesc
+	Err error
+}
+
+func (e *ErrCorrupted) Error() string {
+	if !e.Fd.Zero() {
+		return fmt.Sprintf("%v [file=%v]", e.Err, e.Fd)
+	}
+	return e.Err.Error()
+}
+
+// NewErrCorrupted creates new ErrCorrupted error.
+func NewErrCorrupted(fd storage.FileDesc, err error) error {
+	return &ErrCorrupted{fd, err}
+}
+
+// IsCorrupted returns a boolean indicating whether the error is indicating
+// a corruption.
+func IsCorrupted(err error) bool {
+	switch err.(type) {
+	case *ErrCorrupted:
+		return true
+	case *storage.ErrCorrupted:
+		return true
+	}
+	return false
+}
+
+// ErrMissingFiles is the type that indicating a corruption due to missing
+// files. ErrMissingFiles always wrapped with ErrCorrupted.
+type ErrMissingFiles struct {
+	Fds []storage.FileDesc
+}
+
+func (e *ErrMissingFiles) Error() string { return "file missing" }
+
+// SetFd sets 'file info' of the given error with the given file.
+// Currently only ErrCorrupted is supported, otherwise will do nothing.
+func SetFd(err error, fd storage.FileDesc) error {
+	switch x := err.(type) {
+	case *ErrCorrupted:
+		x.Fd = fd
+		return x
+	}
+	return err
+}

vendor/github.com/syndtr/goleveldb/leveldb/filter.go

@@ -0,0 +1,31 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"github.com/syndtr/goleveldb/leveldb/filter"
+)
+
+type iFilter struct {
+	filter.Filter
+}
+
+func (f iFilter) Contains(filter, key []byte) bool {
+	return f.Filter.Contains(filter, internalKey(key).ukey())
+}
+
+func (f iFilter) NewGenerator() filter.FilterGenerator {
+	return iFilterGenerator{f.Filter.NewGenerator()}
+}
+
+type iFilterGenerator struct {
+	filter.FilterGenerator
+}
+
+func (g iFilterGenerator) Add(key []byte) {
+	g.FilterGenerator.Add(internalKey(key).ukey())
+}

vendor/github.com/syndtr/goleveldb/leveldb/filter/bloom.go

@@ -0,0 +1,116 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package filter
+
+import (
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+func bloomHash(key []byte) uint32 {
+	return util.Hash(key, 0xbc9f1d34)
+}
+
+type bloomFilter int
+
+// The bloom filter serializes its parameters and is backward compatible
+// with respect to them. Therefor, its parameters are not added to its
+// name.
+func (bloomFilter) Name() string {
+	return "leveldb.BuiltinBloomFilter"
+}
+
+func (f bloomFilter) Contains(filter, key []byte) bool {
+	nBytes := len(filter) - 1
+	if nBytes < 1 {
+		return false
+	}
+	nBits := uint32(nBytes * 8)
+
+	// Use the encoded k so that we can read filters generated by
+	// bloom filters created using different parameters.
+	k := filter[nBytes]
+	if k > 30 {
+		// Reserved for potentially new encodings for short bloom filters.
+		// Consider it a match.
+		return true
+	}
+
+	kh := bloomHash(key)
+	delta := (kh >> 17) | (kh << 15) // Rotate right 17 bits
+	for j := uint8(0); j < k; j++ {
+		bitpos := kh % nBits
+		if (uint32(filter[bitpos/8]) & (1 << (bitpos % 8))) == 0 {
+			return false
+		}
+		kh += delta
+	}
+	return true
+}
+
+func (f bloomFilter) NewGenerator() FilterGenerator {
+	// Round down to reduce probing cost a little bit.
+	k := uint8(f * 69 / 100) // 0.69 =~ ln(2)
+	if k < 1 {
+		k = 1
+	} else if k > 30 {
+		k = 30
+	}
+	return &bloomFilterGenerator{
+		n: int(f),
+		k: k,
+	}
+}
+
+type bloomFilterGenerator struct {
+	n int
+	k uint8
+
+	keyHashes []uint32
+}
+
+func (g *bloomFilterGenerator) Add(key []byte) {
+	// Use double-hashing to generate a sequence of hash values.
+	// See analysis in [Kirsch,Mitzenmacher 2006].
+	g.keyHashes = append(g.keyHashes, bloomHash(key))
+}
+
+func (g *bloomFilterGenerator) Generate(b Buffer) {
+	// Compute bloom filter size (in both bits and bytes)
+	nBits := uint32(len(g.keyHashes) * g.n)
+	// For small n, we can see a very high false positive rate.  Fix it
+	// by enforcing a minimum bloom filter length.
+	if nBits < 64 {
+		nBits = 64
+	}
+	nBytes := (nBits + 7) / 8
+	nBits = nBytes * 8
+
+	dest := b.Alloc(int(nBytes) + 1)
+	dest[nBytes] = g.k
+	for _, kh := range g.keyHashes {
+		delta := (kh >> 17) | (kh << 15) // Rotate right 17 bits
+		for j := uint8(0); j < g.k; j++ {
+			bitpos := kh % nBits
+			dest[bitpos/8] |= (1 << (bitpos % 8))
+			kh += delta
+		}
+	}
+
+	g.keyHashes = g.keyHashes[:0]
+}
+
+// NewBloomFilter creates a new initialized bloom filter for given
+// bitsPerKey.
+//
+// Since bitsPerKey is persisted individually for each bloom filter
+// serialization, bloom filters are backwards compatible with respect to
+// changing bitsPerKey. This means that no big performance penalty will
+// be experienced when changing the parameter. See documentation for
+// opt.Options.Filter for more information.
+func NewBloomFilter(bitsPerKey int) Filter {
+	return bloomFilter(bitsPerKey)
+}

vendor/github.com/syndtr/goleveldb/leveldb/filter/filter.go

@@ -0,0 +1,60 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Package filter provides interface and implementation of probabilistic
+// data structure.
+//
+// The filter is resposible for creating small filter from a set of keys.
+// These filter will then used to test whether a key is a member of the set.
+// In many cases, a filter can cut down the number of disk seeks from a
+// handful to a single disk seek per DB.Get call.
+package filter
+
+// Buffer is the interface that wraps basic Alloc, Write and WriteByte methods.
+type Buffer interface {
+	// Alloc allocs n bytes of slice from the buffer. This also advancing
+	// write offset.
+	Alloc(n int) []byte
+
+	// Write appends the contents of p to the buffer.
+	Write(p []byte) (n int, err error)
+
+	// WriteByte appends the byte c to the buffer.
+	WriteByte(c byte) error
+}
+
+// Filter is the filter.
+type Filter interface {
+	// Name returns the name of this policy.
+	//
+	// Note that if the filter encoding changes in an incompatible way,
+	// the name returned by this method must be changed. Otherwise, old
+	// incompatible filters may be passed to methods of this type.
+	Name() string
+
+	// NewGenerator creates a new filter generator.
+	NewGenerator() FilterGenerator
+
+	// Contains returns true if the filter contains the given key.
+	//
+	// The filter are filters generated by the filter generator.
+	Contains(filter, key []byte) bool
+}
+
+// FilterGenerator is the filter generator.
+type FilterGenerator interface {
+	// Add adds a key to the filter generator.
+	//
+	// The key may become invalid after call to this method end, therefor
+	// key must be copied if implementation require keeping key for later
+	// use. The key should not modified directly, doing so may cause
+	// undefined results.
+	Add(key []byte)
+
+	// Generate generates filters based on keys passed so far. After call
+	// to Generate the filter generator maybe resetted, depends on implementation.
+	Generate(b Buffer)
+}

vendor/github.com/syndtr/goleveldb/leveldb/iterator/array_iter.go

@@ -0,0 +1,184 @@
+// Copyright (c) 2014, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package iterator
+
+import (
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+// BasicArray is the interface that wraps basic Len and Search method.
+type BasicArray interface {
+	// Len returns length of the array.
+	Len() int
+
+	// Search finds smallest index that point to a key that is greater
+	// than or equal to the given key.
+	Search(key []byte) int
+}
+
+// Array is the interface that wraps BasicArray and basic Index method.
+type Array interface {
+	BasicArray
+
+	// Index returns key/value pair with index of i.
+	Index(i int) (key, value []byte)
+}
+
+// Array is the interface that wraps BasicArray and basic Get method.
+type ArrayIndexer interface {
+	BasicArray
+
+	// Get returns a new data iterator with index of i.
+	Get(i int) Iterator
+}
+
+type basicArrayIterator struct {
+	util.BasicReleaser
+	array BasicArray
+	pos   int
+	err   error
+}
+
+func (i *basicArrayIterator) Valid() bool {
+	return i.pos >= 0 && i.pos < i.array.Len() && !i.Released()
+}
+
+func (i *basicArrayIterator) First() bool {
+	if i.Released() {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	if i.array.Len() == 0 {
+		i.pos = -1
+		return false
+	}
+	i.pos = 0
+	return true
+}
+
+func (i *basicArrayIterator) Last() bool {
+	if i.Released() {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	n := i.array.Len()
+	if n == 0 {
+		i.pos = 0
+		return false
+	}
+	i.pos = n - 1
+	return true
+}
+
+func (i *basicArrayIterator) Seek(key []byte) bool {
+	if i.Released() {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	n := i.array.Len()
+	if n == 0 {
+		i.pos = 0
+		return false
+	}
+	i.pos = i.array.Search(key)
+	if i.pos >= n {
+		return false
+	}
+	return true
+}
+
+func (i *basicArrayIterator) Next() bool {
+	if i.Released() {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	i.pos++
+	if n := i.array.Len(); i.pos >= n {
+		i.pos = n
+		return false
+	}
+	return true
+}
+
+func (i *basicArrayIterator) Prev() bool {
+	if i.Released() {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	i.pos--
+	if i.pos < 0 {
+		i.pos = -1
+		return false
+	}
+	return true
+}
+
+func (i *basicArrayIterator) Error() error { return i.err }
+
+type arrayIterator struct {
+	basicArrayIterator
+	array      Array
+	pos        int
+	key, value []byte
+}
+
+func (i *arrayIterator) updateKV() {
+	if i.pos == i.basicArrayIterator.pos {
+		return
+	}
+	i.pos = i.basicArrayIterator.pos
+	if i.Valid() {
+		i.key, i.value = i.array.Index(i.pos)
+	} else {
+		i.key = nil
+		i.value = nil
+	}
+}
+
+func (i *arrayIterator) Key() []byte {
+	i.updateKV()
+	return i.key
+}
+
+func (i *arrayIterator) Value() []byte {
+	i.updateKV()
+	return i.value
+}
+
+type arrayIteratorIndexer struct {
+	basicArrayIterator
+	array ArrayIndexer
+}
+
+func (i *arrayIteratorIndexer) Get() Iterator {
+	if i.Valid() {
+		return i.array.Get(i.basicArrayIterator.pos)
+	}
+	return nil
+}
+
+// NewArrayIterator returns an iterator from the given array.
+func NewArrayIterator(array Array) Iterator {
+	return &arrayIterator{
+		basicArrayIterator: basicArrayIterator{array: array, pos: -1},
+		array:              array,
+		pos:                -1,
+	}
+}
+
+// NewArrayIndexer returns an index iterator from the given array.
+func NewArrayIndexer(array ArrayIndexer) IteratorIndexer {
+	return &arrayIteratorIndexer{
+		basicArrayIterator: basicArrayIterator{array: array, pos: -1},
+		array:              array,
+	}
+}

vendor/github.com/syndtr/goleveldb/leveldb/iterator/indexed_iter.go

@@ -0,0 +1,242 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package iterator
+
+import (
+	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+// IteratorIndexer is the interface that wraps CommonIterator and basic Get
+// method. IteratorIndexer provides index for indexed iterator.
+type IteratorIndexer interface {
+	CommonIterator
+
+	// Get returns a new data iterator for the current position, or nil if
+	// done.
+	Get() Iterator
+}
+
+type indexedIterator struct {
+	util.BasicReleaser
+	index  IteratorIndexer
+	strict bool
+
+	data   Iterator
+	err    error
+	errf   func(err error)
+	closed bool
+}
+
+func (i *indexedIterator) setData() {
+	if i.data != nil {
+		i.data.Release()
+	}
+	i.data = i.index.Get()
+}
+
+func (i *indexedIterator) clearData() {
+	if i.data != nil {
+		i.data.Release()
+	}
+	i.data = nil
+}
+
+func (i *indexedIterator) indexErr() {
+	if err := i.index.Error(); err != nil {
+		if i.errf != nil {
+			i.errf(err)
+		}
+		i.err = err
+	}
+}
+
+func (i *indexedIterator) dataErr() bool {
+	if err := i.data.Error(); err != nil {
+		if i.errf != nil {
+			i.errf(err)
+		}
+		if i.strict || !errors.IsCorrupted(err) {
+			i.err = err
+			return true
+		}
+	}
+	return false
+}
+
+func (i *indexedIterator) Valid() bool {
+	return i.data != nil && i.data.Valid()
+}
+
+func (i *indexedIterator) First() bool {
+	if i.err != nil {
+		return false
+	} else if i.Released() {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	if !i.index.First() {
+		i.indexErr()
+		i.clearData()
+		return false
+	}
+	i.setData()
+	return i.Next()
+}
+
+func (i *indexedIterator) Last() bool {
+	if i.err != nil {
+		return false
+	} else if i.Released() {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	if !i.index.Last() {
+		i.indexErr()
+		i.clearData()
+		return false
+	}
+	i.setData()
+	if !i.data.Last() {
+		if i.dataErr() {
+			return false
+		}
+		i.clearData()
+		return i.Prev()
+	}
+	return true
+}
+
+func (i *indexedIterator) Seek(key []byte) bool {
+	if i.err != nil {
+		return false
+	} else if i.Released() {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	if !i.index.Seek(key) {
+		i.indexErr()
+		i.clearData()
+		return false
+	}
+	i.setData()
+	if !i.data.Seek(key) {
+		if i.dataErr() {
+			return false
+		}
+		i.clearData()
+		return i.Next()
+	}
+	return true
+}
+
+func (i *indexedIterator) Next() bool {
+	if i.err != nil {
+		return false
+	} else if i.Released() {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	switch {
+	case i.data != nil && !i.data.Next():
+		if i.dataErr() {
+			return false
+		}
+		i.clearData()
+		fallthrough
+	case i.data == nil:
+		if !i.index.Next() {
+			i.indexErr()
+			return false
+		}
+		i.setData()
+		return i.Next()
+	}
+	return true
+}
+
+func (i *indexedIterator) Prev() bool {
+	if i.err != nil {
+		return false
+	} else if i.Released() {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	switch {
+	case i.data != nil && !i.data.Prev():
+		if i.dataErr() {
+			return false
+		}
+		i.clearData()
+		fallthrough
+	case i.data == nil:
+		if !i.index.Prev() {
+			i.indexErr()
+			return false
+		}
+		i.setData()
+		if !i.data.Last() {
+			if i.dataErr() {
+				return false
+			}
+			i.clearData()
+			return i.Prev()
+		}
+	}
+	return true
+}
+
+func (i *indexedIterator) Key() []byte {
+	if i.data == nil {
+		return nil
+	}
+	return i.data.Key()
+}
+
+func (i *indexedIterator) Value() []byte {
+	if i.data == nil {
+		return nil
+	}
+	return i.data.Value()
+}
+
+func (i *indexedIterator) Release() {
+	i.clearData()
+	i.index.Release()
+	i.BasicReleaser.Release()
+}
+
+func (i *indexedIterator) Error() error {
+	if i.err != nil {
+		return i.err
+	}
+	if err := i.index.Error(); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (i *indexedIterator) SetErrorCallback(f func(err error)) {
+	i.errf = f
+}
+
+// NewIndexedIterator returns an 'indexed iterator'. An index is iterator
+// that returns another iterator, a 'data iterator'. A 'data iterator' is the
+// iterator that contains actual key/value pairs.
+//
+// If strict is true the any 'corruption errors' (i.e errors.IsCorrupted(err) == true)
+// won't be ignored and will halt 'indexed iterator', otherwise the iterator will
+// continue to the next 'data iterator'. Corruption on 'index iterator' will not be
+// ignored and will halt the iterator.
+func NewIndexedIterator(index IteratorIndexer, strict bool) Iterator {
+	return &indexedIterator{index: index, strict: strict}
+}

vendor/github.com/syndtr/goleveldb/leveldb/iterator/iter.go

@@ -0,0 +1,132 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Package iterator provides interface and implementation to traverse over
+// contents of a database.
+package iterator
+
+import (
+	"errors"
+
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+var (
+	ErrIterReleased = errors.New("leveldb/iterator: iterator released")
+)
+
+// IteratorSeeker is the interface that wraps the 'seeks method'.
+type IteratorSeeker interface {
+	// First moves the iterator to the first key/value pair. If the iterator
+	// only contains one key/value pair then First and Last would moves
+	// to the same key/value pair.
+	// It returns whether such pair exist.
+	First() bool
+
+	// Last moves the iterator to the last key/value pair. If the iterator
+	// only contains one key/value pair then First and Last would moves
+	// to the same key/value pair.
+	// It returns whether such pair exist.
+	Last() bool
+
+	// Seek moves the iterator to the first key/value pair whose key is greater
+	// than or equal to the given key.
+	// It returns whether such pair exist.
+	//
+	// It is safe to modify the contents of the argument after Seek returns.
+	Seek(key []byte) bool
+
+	// Next moves the iterator to the next key/value pair.
+	// It returns false if the iterator is exhausted.
+	Next() bool
+
+	// Prev moves the iterator to the previous key/value pair.
+	// It returns false if the iterator is exhausted.
+	Prev() bool
+}
+
+// CommonIterator is the interface that wraps common iterator methods.
+type CommonIterator interface {
+	IteratorSeeker
+
+	// util.Releaser is the interface that wraps basic Release method.
+	// When called Release will releases any resources associated with the
+	// iterator.
+	util.Releaser
+
+	// util.ReleaseSetter is the interface that wraps the basic SetReleaser
+	// method.
+	util.ReleaseSetter
+
+	// TODO: Remove this when ready.
+	Valid() bool
+
+	// Error returns any accumulated error. Exhausting all the key/value pairs
+	// is not considered to be an error.
+	Error() error
+}
+
+// Iterator iterates over a DB's key/value pairs in key order.
+//
+// When encounter an error any 'seeks method' will return false and will
+// yield no key/value pairs. The error can be queried by calling the Error
+// method. Calling Release is still necessary.
+//
+// An iterator must be released after use, but it is not necessary to read
+// an iterator until exhaustion.
+// Also, an iterator is not necessarily safe for concurrent use, but it is
+// safe to use multiple iterators concurrently, with each in a dedicated
+// goroutine.
+type Iterator interface {
+	CommonIterator
+
+	// Key returns the key of the current key/value pair, or nil if done.
+	// The caller should not modify the contents of the returned slice, and
+	// its contents may change on the next call to any 'seeks method'.
+	Key() []byte
+
+	// Value returns the value of the current key/value pair, or nil if done.
+	// The caller should not modify the contents of the returned slice, and
+	// its contents may change on the next call to any 'seeks method'.
+	Value() []byte
+}
+
+// ErrorCallbackSetter is the interface that wraps basic SetErrorCallback
+// method.
+//
+// ErrorCallbackSetter implemented by indexed and merged iterator.
+type ErrorCallbackSetter interface {
+	// SetErrorCallback allows set an error callback of the corresponding
+	// iterator. Use nil to clear the callback.
+	SetErrorCallback(f func(err error))
+}
+
+type emptyIterator struct {
+	util.BasicReleaser
+	err error
+}
+
+func (i *emptyIterator) rErr() {
+	if i.err == nil && i.Released() {
+		i.err = ErrIterReleased
+	}
+}
+
+func (*emptyIterator) Valid() bool            { return false }
+func (i *emptyIterator) First() bool          { i.rErr(); return false }
+func (i *emptyIterator) Last() bool           { i.rErr(); return false }
+func (i *emptyIterator) Seek(key []byte) bool { i.rErr(); return false }
+func (i *emptyIterator) Next() bool           { i.rErr(); return false }
+func (i *emptyIterator) Prev() bool           { i.rErr(); return false }
+func (*emptyIterator) Key() []byte            { return nil }
+func (*emptyIterator) Value() []byte          { return nil }
+func (i *emptyIterator) Error() error         { return i.err }
+
+// NewEmptyIterator creates an empty iterator. The err parameter can be
+// nil, but if not nil the given err will be returned by Error method.
+func NewEmptyIterator(err error) Iterator {
+	return &emptyIterator{err: err}
+}

vendor/github.com/syndtr/goleveldb/leveldb/iterator/merged_iter.go

@@ -0,0 +1,304 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package iterator
+
+import (
+	"github.com/syndtr/goleveldb/leveldb/comparer"
+	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+type dir int
+
+const (
+	dirReleased dir = iota - 1
+	dirSOI
+	dirEOI
+	dirBackward
+	dirForward
+)
+
+type mergedIterator struct {
+	cmp    comparer.Comparer
+	iters  []Iterator
+	strict bool
+
+	keys     [][]byte
+	index    int
+	dir      dir
+	err      error
+	errf     func(err error)
+	releaser util.Releaser
+}
+
+func assertKey(key []byte) []byte {
+	if key == nil {
+		panic("leveldb/iterator: nil key")
+	}
+	return key
+}
+
+func (i *mergedIterator) iterErr(iter Iterator) bool {
+	if err := iter.Error(); err != nil {
+		if i.errf != nil {
+			i.errf(err)
+		}
+		if i.strict || !errors.IsCorrupted(err) {
+			i.err = err
+			return true
+		}
+	}
+	return false
+}
+
+func (i *mergedIterator) Valid() bool {
+	return i.err == nil && i.dir > dirEOI
+}
+
+func (i *mergedIterator) First() bool {
+	if i.err != nil {
+		return false
+	} else if i.dir == dirReleased {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	for x, iter := range i.iters {
+		switch {
+		case iter.First():
+			i.keys[x] = assertKey(iter.Key())
+		case i.iterErr(iter):
+			return false
+		default:
+			i.keys[x] = nil
+		}
+	}
+	i.dir = dirSOI
+	return i.next()
+}
+
+func (i *mergedIterator) Last() bool {
+	if i.err != nil {
+		return false
+	} else if i.dir == dirReleased {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	for x, iter := range i.iters {
+		switch {
+		case iter.Last():
+			i.keys[x] = assertKey(iter.Key())
+		case i.iterErr(iter):
+			return false
+		default:
+			i.keys[x] = nil
+		}
+	}
+	i.dir = dirEOI
+	return i.prev()
+}
+
+func (i *mergedIterator) Seek(key []byte) bool {
+	if i.err != nil {
+		return false
+	} else if i.dir == dirReleased {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	for x, iter := range i.iters {
+		switch {
+		case iter.Seek(key):
+			i.keys[x] = assertKey(iter.Key())
+		case i.iterErr(iter):
+			return false
+		default:
+			i.keys[x] = nil
+		}
+	}
+	i.dir = dirSOI
+	return i.next()
+}
+
+func (i *mergedIterator) next() bool {
+	var key []byte
+	if i.dir == dirForward {
+		key = i.keys[i.index]
+	}
+	for x, tkey := range i.keys {
+		if tkey != nil && (key == nil || i.cmp.Compare(tkey, key) < 0) {
+			key = tkey
+			i.index = x
+		}
+	}
+	if key == nil {
+		i.dir = dirEOI
+		return false
+	}
+	i.dir = dirForward
+	return true
+}
+
+func (i *mergedIterator) Next() bool {
+	if i.dir == dirEOI || i.err != nil {
+		return false
+	} else if i.dir == dirReleased {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	switch i.dir {
+	case dirSOI:
+		return i.First()
+	case dirBackward:
+		key := append([]byte{}, i.keys[i.index]...)
+		if !i.Seek(key) {
+			return false
+		}
+		return i.Next()
+	}
+
+	x := i.index
+	iter := i.iters[x]
+	switch {
+	case iter.Next():
+		i.keys[x] = assertKey(iter.Key())
+	case i.iterErr(iter):
+		return false
+	default:
+		i.keys[x] = nil
+	}
+	return i.next()
+}
+
+func (i *mergedIterator) prev() bool {
+	var key []byte
+	if i.dir == dirBackward {
+		key = i.keys[i.index]
+	}
+	for x, tkey := range i.keys {
+		if tkey != nil && (key == nil || i.cmp.Compare(tkey, key) > 0) {
+			key = tkey
+			i.index = x
+		}
+	}
+	if key == nil {
+		i.dir = dirSOI
+		return false
+	}
+	i.dir = dirBackward
+	return true
+}
+
+func (i *mergedIterator) Prev() bool {
+	if i.dir == dirSOI || i.err != nil {
+		return false
+	} else if i.dir == dirReleased {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	switch i.dir {
+	case dirEOI:
+		return i.Last()
+	case dirForward:
+		key := append([]byte{}, i.keys[i.index]...)
+		for x, iter := range i.iters {
+			if x == i.index {
+				continue
+			}
+			seek := iter.Seek(key)
+			switch {
+			case seek && iter.Prev(), !seek && iter.Last():
+				i.keys[x] = assertKey(iter.Key())
+			case i.iterErr(iter):
+				return false
+			default:
+				i.keys[x] = nil
+			}
+		}
+	}
+
+	x := i.index
+	iter := i.iters[x]
+	switch {
+	case iter.Prev():
+		i.keys[x] = assertKey(iter.Key())
+	case i.iterErr(iter):
+		return false
+	default:
+		i.keys[x] = nil
+	}
+	return i.prev()
+}
+
+func (i *mergedIterator) Key() []byte {
+	if i.err != nil || i.dir <= dirEOI {
+		return nil
+	}
+	return i.keys[i.index]
+}
+
+func (i *mergedIterator) Value() []byte {
+	if i.err != nil || i.dir <= dirEOI {
+		return nil
+	}
+	return i.iters[i.index].Value()
+}
+
+func (i *mergedIterator) Release() {
+	if i.dir != dirReleased {
+		i.dir = dirReleased
+		for _, iter := range i.iters {
+			iter.Release()
+		}
+		i.iters = nil
+		i.keys = nil
+		if i.releaser != nil {
+			i.releaser.Release()
+			i.releaser = nil
+		}
+	}
+}
+
+func (i *mergedIterator) SetReleaser(releaser util.Releaser) {
+	if i.dir == dirReleased {
+		panic(util.ErrReleased)
+	}
+	if i.releaser != nil && releaser != nil {
+		panic(util.ErrHasReleaser)
+	}
+	i.releaser = releaser
+}
+
+func (i *mergedIterator) Error() error {
+	return i.err
+}
+
+func (i *mergedIterator) SetErrorCallback(f func(err error)) {
+	i.errf = f
+}
+
+// NewMergedIterator returns an iterator that merges its input. Walking the
+// resultant iterator will return all key/value pairs of all input iterators
+// in strictly increasing key order, as defined by cmp.
+// The input's key ranges may overlap, but there are assumed to be no duplicate
+// keys: if iters[i] contains a key k then iters[j] will not contain that key k.
+// None of the iters may be nil.
+//
+// If strict is true the any 'corruption errors' (i.e errors.IsCorrupted(err) == true)
+// won't be ignored and will halt 'merged iterator', otherwise the iterator will
+// continue to the next 'input iterator'.
+func NewMergedIterator(iters []Iterator, cmp comparer.Comparer, strict bool) Iterator {
+	return &mergedIterator{
+		iters:  iters,
+		cmp:    cmp,
+		strict: strict,
+		keys:   make([][]byte, len(iters)),
+	}
+}

vendor/github.com/syndtr/goleveldb/leveldb/journal/journal.go

@@ -0,0 +1,524 @@
+// Copyright 2011 The LevelDB-Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Taken from: https://code.google.com/p/leveldb-go/source/browse/leveldb/record/record.go?r=1d5ccbe03246da926391ee12d1c6caae054ff4b0
+// License, authors and contributors informations can be found at bellow URLs respectively:
+// 	https://code.google.com/p/leveldb-go/source/browse/LICENSE
+//	https://code.google.com/p/leveldb-go/source/browse/AUTHORS
+//  https://code.google.com/p/leveldb-go/source/browse/CONTRIBUTORS
+
+// Package journal reads and writes sequences of journals. Each journal is a stream
+// of bytes that completes before the next journal starts.
+//
+// When reading, call Next to obtain an io.Reader for the next journal. Next will
+// return io.EOF when there are no more journals. It is valid to call Next
+// without reading the current journal to exhaustion.
+//
+// When writing, call Next to obtain an io.Writer for the next journal. Calling
+// Next finishes the current journal. Call Close to finish the final journal.
+//
+// Optionally, call Flush to finish the current journal and flush the underlying
+// writer without starting a new journal. To start a new journal after flushing,
+// call Next.
+//
+// Neither Readers or Writers are safe to use concurrently.
+//
+// Example code:
+//	func read(r io.Reader) ([]string, error) {
+//		var ss []string
+//		journals := journal.NewReader(r, nil, true, true)
+//		for {
+//			j, err := journals.Next()
+//			if err == io.EOF {
+//				break
+//			}
+//			if err != nil {
+//				return nil, err
+//			}
+//			s, err := ioutil.ReadAll(j)
+//			if err != nil {
+//				return nil, err
+//			}
+//			ss = append(ss, string(s))
+//		}
+//		return ss, nil
+//	}
+//
+//	func write(w io.Writer, ss []string) error {
+//		journals := journal.NewWriter(w)
+//		for _, s := range ss {
+//			j, err := journals.Next()
+//			if err != nil {
+//				return err
+//			}
+//			if _, err := j.Write([]byte(s)), err != nil {
+//				return err
+//			}
+//		}
+//		return journals.Close()
+//	}
+//
+// The wire format is that the stream is divided into 32KiB blocks, and each
+// block contains a number of tightly packed chunks. Chunks cannot cross block
+// boundaries. The last block may be shorter than 32 KiB. Any unused bytes in a
+// block must be zero.
+//
+// A journal maps to one or more chunks. Each chunk has a 7 byte header (a 4
+// byte checksum, a 2 byte little-endian uint16 length, and a 1 byte chunk type)
+// followed by a payload. The checksum is over the chunk type and the payload.
+//
+// There are four chunk types: whether the chunk is the full journal, or the
+// first, middle or last chunk of a multi-chunk journal. A multi-chunk journal
+// has one first chunk, zero or more middle chunks, and one last chunk.
+//
+// The wire format allows for limited recovery in the face of data corruption:
+// on a format error (such as a checksum mismatch), the reader moves to the
+// next block and looks for the next full or first chunk.
+package journal
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+
+	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+// These constants are part of the wire format and should not be changed.
+const (
+	fullChunkType   = 1
+	firstChunkType  = 2
+	middleChunkType = 3
+	lastChunkType   = 4
+)
+
+const (
+	blockSize  = 32 * 1024
+	headerSize = 7
+)
+
+type flusher interface {
+	Flush() error
+}
+
+// ErrCorrupted is the error type that generated by corrupted block or chunk.
+type ErrCorrupted struct {
+	Size   int
+	Reason string
+}
+
+func (e *ErrCorrupted) Error() string {
+	return fmt.Sprintf("leveldb/journal: block/chunk corrupted: %s (%d bytes)", e.Reason, e.Size)
+}
+
+// Dropper is the interface that wrap simple Drop method. The Drop
+// method will be called when the journal reader dropping a block or chunk.
+type Dropper interface {
+	Drop(err error)
+}
+
+// Reader reads journals from an underlying io.Reader.
+type Reader struct {
+	// r is the underlying reader.
+	r io.Reader
+	// the dropper.
+	dropper Dropper
+	// strict flag.
+	strict bool
+	// checksum flag.
+	checksum bool
+	// seq is the sequence number of the current journal.
+	seq int
+	// buf[i:j] is the unread portion of the current chunk's payload.
+	// The low bound, i, excludes the chunk header.
+	i, j int
+	// n is the number of bytes of buf that are valid. Once reading has started,
+	// only the final block can have n < blockSize.
+	n int
+	// last is whether the current chunk is the last chunk of the journal.
+	last bool
+	// err is any accumulated error.
+	err error
+	// buf is the buffer.
+	buf [blockSize]byte
+}
+
+// NewReader returns a new reader. The dropper may be nil, and if
+// strict is true then corrupted or invalid chunk will halt the journal
+// reader entirely.
+func NewReader(r io.Reader, dropper Dropper, strict, checksum bool) *Reader {
+	return &Reader{
+		r:        r,
+		dropper:  dropper,
+		strict:   strict,
+		checksum: checksum,
+		last:     true,
+	}
+}
+
+var errSkip = errors.New("leveldb/journal: skipped")
+
+func (r *Reader) corrupt(n int, reason string, skip bool) error {
+	if r.dropper != nil {
+		r.dropper.Drop(&ErrCorrupted{n, reason})
+	}
+	if r.strict && !skip {
+		r.err = errors.NewErrCorrupted(storage.FileDesc{}, &ErrCorrupted{n, reason})
+		return r.err
+	}
+	return errSkip
+}
+
+// nextChunk sets r.buf[r.i:r.j] to hold the next chunk's payload, reading the
+// next block into the buffer if necessary.
+func (r *Reader) nextChunk(first bool) error {
+	for {
+		if r.j+headerSize <= r.n {
+			checksum := binary.LittleEndian.Uint32(r.buf[r.j+0 : r.j+4])
+			length := binary.LittleEndian.Uint16(r.buf[r.j+4 : r.j+6])
+			chunkType := r.buf[r.j+6]
+			unprocBlock := r.n - r.j
+			if checksum == 0 && length == 0 && chunkType == 0 {
+				// Drop entire block.
+				r.i = r.n
+				r.j = r.n
+				return r.corrupt(unprocBlock, "zero header", false)
+			}
+			if chunkType < fullChunkType || chunkType > lastChunkType {
+				// Drop entire block.
+				r.i = r.n
+				r.j = r.n
+				return r.corrupt(unprocBlock, fmt.Sprintf("invalid chunk type %#x", chunkType), false)
+			}
+			r.i = r.j + headerSize
+			r.j = r.j + headerSize + int(length)
+			if r.j > r.n {
+				// Drop entire block.
+				r.i = r.n
+				r.j = r.n
+				return r.corrupt(unprocBlock, "chunk length overflows block", false)
+			} else if r.checksum && checksum != util.NewCRC(r.buf[r.i-1:r.j]).Value() {
+				// Drop entire block.
+				r.i = r.n
+				r.j = r.n
+				return r.corrupt(unprocBlock, "checksum mismatch", false)
+			}
+			if first && chunkType != fullChunkType && chunkType != firstChunkType {
+				chunkLength := (r.j - r.i) + headerSize
+				r.i = r.j
+				// Report the error, but skip it.
+				return r.corrupt(chunkLength, "orphan chunk", true)
+			}
+			r.last = chunkType == fullChunkType || chunkType == lastChunkType
+			return nil
+		}
+
+		// The last block.
+		if r.n < blockSize && r.n > 0 {
+			if !first {
+				return r.corrupt(0, "missing chunk part", false)
+			}
+			r.err = io.EOF
+			return r.err
+		}
+
+		// Read block.
+		n, err := io.ReadFull(r.r, r.buf[:])
+		if err != nil && err != io.EOF && err != io.ErrUnexpectedEOF {
+			return err
+		}
+		if n == 0 {
+			if !first {
+				return r.corrupt(0, "missing chunk part", false)
+			}
+			r.err = io.EOF
+			return r.err
+		}
+		r.i, r.j, r.n = 0, 0, n
+	}
+}
+
+// Next returns a reader for the next journal. It returns io.EOF if there are no
+// more journals. The reader returned becomes stale after the next Next call,
+// and should no longer be used. If strict is false, the reader will returns
+// io.ErrUnexpectedEOF error when found corrupted journal.
+func (r *Reader) Next() (io.Reader, error) {
+	r.seq++
+	if r.err != nil {
+		return nil, r.err
+	}
+	r.i = r.j
+	for {
+		if err := r.nextChunk(true); err == nil {
+			break
+		} else if err != errSkip {
+			return nil, err
+		}
+	}
+	return &singleReader{r, r.seq, nil}, nil
+}
+
+// Reset resets the journal reader, allows reuse of the journal reader. Reset returns
+// last accumulated error.
+func (r *Reader) Reset(reader io.Reader, dropper Dropper, strict, checksum bool) error {
+	r.seq++
+	err := r.err
+	r.r = reader
+	r.dropper = dropper
+	r.strict = strict
+	r.checksum = checksum
+	r.i = 0
+	r.j = 0
+	r.n = 0
+	r.last = true
+	r.err = nil
+	return err
+}
+
+type singleReader struct {
+	r   *Reader
+	seq int
+	err error
+}
+
+func (x *singleReader) Read(p []byte) (int, error) {
+	r := x.r
+	if r.seq != x.seq {
+		return 0, errors.New("leveldb/journal: stale reader")
+	}
+	if x.err != nil {
+		return 0, x.err
+	}
+	if r.err != nil {
+		return 0, r.err
+	}
+	for r.i == r.j {
+		if r.last {
+			return 0, io.EOF
+		}
+		x.err = r.nextChunk(false)
+		if x.err != nil {
+			if x.err == errSkip {
+				x.err = io.ErrUnexpectedEOF
+			}
+			return 0, x.err
+		}
+	}
+	n := copy(p, r.buf[r.i:r.j])
+	r.i += n
+	return n, nil
+}
+
+func (x *singleReader) ReadByte() (byte, error) {
+	r := x.r
+	if r.seq != x.seq {
+		return 0, errors.New("leveldb/journal: stale reader")
+	}
+	if x.err != nil {
+		return 0, x.err
+	}
+	if r.err != nil {
+		return 0, r.err
+	}
+	for r.i == r.j {
+		if r.last {
+			return 0, io.EOF
+		}
+		x.err = r.nextChunk(false)
+		if x.err != nil {
+			if x.err == errSkip {
+				x.err = io.ErrUnexpectedEOF
+			}
+			return 0, x.err
+		}
+	}
+	c := r.buf[r.i]
+	r.i++
+	return c, nil
+}
+
+// Writer writes journals to an underlying io.Writer.
+type Writer struct {
+	// w is the underlying writer.
+	w io.Writer
+	// seq is the sequence number of the current journal.
+	seq int
+	// f is w as a flusher.
+	f flusher
+	// buf[i:j] is the bytes that will become the current chunk.
+	// The low bound, i, includes the chunk header.
+	i, j int
+	// buf[:written] has already been written to w.
+	// written is zero unless Flush has been called.
+	written int
+	// first is whether the current chunk is the first chunk of the journal.
+	first bool
+	// pending is whether a chunk is buffered but not yet written.
+	pending bool
+	// err is any accumulated error.
+	err error
+	// buf is the buffer.
+	buf [blockSize]byte
+}
+
+// NewWriter returns a new Writer.
+func NewWriter(w io.Writer) *Writer {
+	f, _ := w.(flusher)
+	return &Writer{
+		w: w,
+		f: f,
+	}
+}
+
+// fillHeader fills in the header for the pending chunk.
+func (w *Writer) fillHeader(last bool) {
+	if w.i+headerSize > w.j || w.j > blockSize {
+		panic("leveldb/journal: bad writer state")
+	}
+	if last {
+		if w.first {
+			w.buf[w.i+6] = fullChunkType
+		} else {
+			w.buf[w.i+6] = lastChunkType
+		}
+	} else {
+		if w.first {
+			w.buf[w.i+6] = firstChunkType
+		} else {
+			w.buf[w.i+6] = middleChunkType
+		}
+	}
+	binary.LittleEndian.PutUint32(w.buf[w.i+0:w.i+4], util.NewCRC(w.buf[w.i+6:w.j]).Value())
+	binary.LittleEndian.PutUint16(w.buf[w.i+4:w.i+6], uint16(w.j-w.i-headerSize))
+}
+
+// writeBlock writes the buffered block to the underlying writer, and reserves
+// space for the next chunk's header.
+func (w *Writer) writeBlock() {
+	_, w.err = w.w.Write(w.buf[w.written:])
+	w.i = 0
+	w.j = headerSize
+	w.written = 0
+}
+
+// writePending finishes the current journal and writes the buffer to the
+// underlying writer.
+func (w *Writer) writePending() {
+	if w.err != nil {
+		return
+	}
+	if w.pending {
+		w.fillHeader(true)
+		w.pending = false
+	}
+	_, w.err = w.w.Write(w.buf[w.written:w.j])
+	w.written = w.j
+}
+
+// Close finishes the current journal and closes the writer.
+func (w *Writer) Close() error {
+	w.seq++
+	w.writePending()
+	if w.err != nil {
+		return w.err
+	}
+	w.err = errors.New("leveldb/journal: closed Writer")
+	return nil
+}
+
+// Flush finishes the current journal, writes to the underlying writer, and
+// flushes it if that writer implements interface{ Flush() error }.
+func (w *Writer) Flush() error {
+	w.seq++
+	w.writePending()
+	if w.err != nil {
+		return w.err
+	}
+	if w.f != nil {
+		w.err = w.f.Flush()
+		return w.err
+	}
+	return nil
+}
+
+// Reset resets the journal writer, allows reuse of the journal writer. Reset
+// will also closes the journal writer if not already.
+func (w *Writer) Reset(writer io.Writer) (err error) {
+	w.seq++
+	if w.err == nil {
+		w.writePending()
+		err = w.err
+	}
+	w.w = writer
+	w.f, _ = writer.(flusher)
+	w.i = 0
+	w.j = 0
+	w.written = 0
+	w.first = false
+	w.pending = false
+	w.err = nil
+	return
+}
+
+// Next returns a writer for the next journal. The writer returned becomes stale
+// after the next Close, Flush or Next call, and should no longer be used.
+func (w *Writer) Next() (io.Writer, error) {
+	w.seq++
+	if w.err != nil {
+		return nil, w.err
+	}
+	if w.pending {
+		w.fillHeader(true)
+	}
+	w.i = w.j
+	w.j = w.j + headerSize
+	// Check if there is room in the block for the header.
+	if w.j > blockSize {
+		// Fill in the rest of the block with zeroes.
+		for k := w.i; k < blockSize; k++ {
+			w.buf[k] = 0
+		}
+		w.writeBlock()
+		if w.err != nil {
+			return nil, w.err
+		}
+	}
+	w.first = true
+	w.pending = true
+	return singleWriter{w, w.seq}, nil
+}
+
+type singleWriter struct {
+	w   *Writer
+	seq int
+}
+
+func (x singleWriter) Write(p []byte) (int, error) {
+	w := x.w
+	if w.seq != x.seq {
+		return 0, errors.New("leveldb/journal: stale writer")
+	}
+	if w.err != nil {
+		return 0, w.err
+	}
+	n0 := len(p)
+	for len(p) > 0 {
+		// Write a block, if it is full.
+		if w.j == blockSize {
+			w.fillHeader(false)
+			w.writeBlock()
+			if w.err != nil {
+				return 0, w.err
+			}
+			w.first = false
+		}
+		// Copy bytes into the buffer.
+		n := copy(w.buf[w.j:], p)
+		w.j += n
+		p = p[n:]
+	}
+	return n0, nil
+}

vendor/github.com/syndtr/goleveldb/leveldb/key.go

@@ -0,0 +1,143 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"encoding/binary"
+	"fmt"
+
+	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+)
+
+// ErrInternalKeyCorrupted records internal key corruption.
+type ErrInternalKeyCorrupted struct {
+	Ikey   []byte
+	Reason string
+}
+
+func (e *ErrInternalKeyCorrupted) Error() string {
+	return fmt.Sprintf("leveldb: internal key %q corrupted: %s", e.Ikey, e.Reason)
+}
+
+func newErrInternalKeyCorrupted(ikey []byte, reason string) error {
+	return errors.NewErrCorrupted(storage.FileDesc{}, &ErrInternalKeyCorrupted{append([]byte{}, ikey...), reason})
+}
+
+type keyType uint
+
+func (kt keyType) String() string {
+	switch kt {
+	case keyTypeDel:
+		return "d"
+	case keyTypeVal:
+		return "v"
+	}
+	return fmt.Sprintf("<invalid:%#x>", uint(kt))
+}
+
+// Value types encoded as the last component of internal keys.
+// Don't modify; this value are saved to disk.
+const (
+	keyTypeDel = keyType(0)
+	keyTypeVal = keyType(1)
+)
+
+// keyTypeSeek defines the keyType that should be passed when constructing an
+// internal key for seeking to a particular sequence number (since we
+// sort sequence numbers in decreasing order and the value type is
+// embedded as the low 8 bits in the sequence number in internal keys,
+// we need to use the highest-numbered ValueType, not the lowest).
+const keyTypeSeek = keyTypeVal
+
+const (
+	// Maximum value possible for sequence number; the 8-bits are
+	// used by value type, so its can packed together in single
+	// 64-bit integer.
+	keyMaxSeq = (uint64(1) << 56) - 1
+	// Maximum value possible for packed sequence number and type.
+	keyMaxNum = (keyMaxSeq << 8) | uint64(keyTypeSeek)
+)
+
+// Maximum number encoded in bytes.
+var keyMaxNumBytes = make([]byte, 8)
+
+func init() {
+	binary.LittleEndian.PutUint64(keyMaxNumBytes, keyMaxNum)
+}
+
+type internalKey []byte
+
+func makeInternalKey(dst, ukey []byte, seq uint64, kt keyType) internalKey {
+	if seq > keyMaxSeq {
+		panic("leveldb: invalid sequence number")
+	} else if kt > keyTypeVal {
+		panic("leveldb: invalid type")
+	}
+
+	dst = ensureBuffer(dst, len(ukey)+8)
+	copy(dst, ukey)
+	binary.LittleEndian.PutUint64(dst[len(ukey):], (seq<<8)|uint64(kt))
+	return internalKey(dst)
+}
+
+func parseInternalKey(ik []byte) (ukey []byte, seq uint64, kt keyType, err error) {
+	if len(ik) < 8 {
+		return nil, 0, 0, newErrInternalKeyCorrupted(ik, "invalid length")
+	}
+	num := binary.LittleEndian.Uint64(ik[len(ik)-8:])
+	seq, kt = uint64(num>>8), keyType(num&0xff)
+	if kt > keyTypeVal {
+		return nil, 0, 0, newErrInternalKeyCorrupted(ik, "invalid type")
+	}
+	ukey = ik[:len(ik)-8]
+	return
+}
+
+func validInternalKey(ik []byte) bool {
+	_, _, _, err := parseInternalKey(ik)
+	return err == nil
+}
+
+func (ik internalKey) assert() {
+	if ik == nil {
+		panic("leveldb: nil internalKey")
+	}
+	if len(ik) < 8 {
+		panic(fmt.Sprintf("leveldb: internal key %q, len=%d: invalid length", []byte(ik), len(ik)))
+	}
+}
+
+func (ik internalKey) ukey() []byte {
+	ik.assert()
+	return ik[:len(ik)-8]
+}
+
+func (ik internalKey) num() uint64 {
+	ik.assert()
+	return binary.LittleEndian.Uint64(ik[len(ik)-8:])
+}
+
+func (ik internalKey) parseNum() (seq uint64, kt keyType) {
+	num := ik.num()
+	seq, kt = uint64(num>>8), keyType(num&0xff)
+	if kt > keyTypeVal {
+		panic(fmt.Sprintf("leveldb: internal key %q, len=%d: invalid type %#x", []byte(ik), len(ik), kt))
+	}
+	return
+}
+
+func (ik internalKey) String() string {
+	if ik == nil {
+		return "<nil>"
+	}
+
+	if ukey, seq, kt, err := parseInternalKey(ik); err == nil {
+		return fmt.Sprintf("%s,%s%d", shorten(string(ukey)), kt, seq)
+	}
+	return fmt.Sprintf("<invalid:%#x>", []byte(ik))
+}

vendor/github.com/syndtr/goleveldb/leveldb/memdb/memdb.go

@@ -0,0 +1,479 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Package memdb provides in-memory key/value database implementation.
+package memdb
+
+import (
+	"math/rand"
+	"sync"
+
+	"github.com/syndtr/goleveldb/leveldb/comparer"
+	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/iterator"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+// Common errors.
+var (
+	ErrNotFound     = errors.ErrNotFound
+	ErrIterReleased = errors.New("leveldb/memdb: iterator released")
+)
+
+const tMaxHeight = 12
+
+type dbIter struct {
+	util.BasicReleaser
+	p          *DB
+	slice      *util.Range
+	node       int
+	forward    bool
+	key, value []byte
+	err        error
+}
+
+func (i *dbIter) fill(checkStart, checkLimit bool) bool {
+	if i.node != 0 {
+		n := i.p.nodeData[i.node]
+		m := n + i.p.nodeData[i.node+nKey]
+		i.key = i.p.kvData[n:m]
+		if i.slice != nil {
+			switch {
+			case checkLimit && i.slice.Limit != nil && i.p.cmp.Compare(i.key, i.slice.Limit) >= 0:
+				fallthrough
+			case checkStart && i.slice.Start != nil && i.p.cmp.Compare(i.key, i.slice.Start) < 0:
+				i.node = 0
+				goto bail
+			}
+		}
+		i.value = i.p.kvData[m : m+i.p.nodeData[i.node+nVal]]
+		return true
+	}
+bail:
+	i.key = nil
+	i.value = nil
+	return false
+}
+
+func (i *dbIter) Valid() bool {
+	return i.node != 0
+}
+
+func (i *dbIter) First() bool {
+	if i.Released() {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	i.forward = true
+	i.p.mu.RLock()
+	defer i.p.mu.RUnlock()
+	if i.slice != nil && i.slice.Start != nil {
+		i.node, _ = i.p.findGE(i.slice.Start, false)
+	} else {
+		i.node = i.p.nodeData[nNext]
+	}
+	return i.fill(false, true)
+}
+
+func (i *dbIter) Last() bool {
+	if i.Released() {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	i.forward = false
+	i.p.mu.RLock()
+	defer i.p.mu.RUnlock()
+	if i.slice != nil && i.slice.Limit != nil {
+		i.node = i.p.findLT(i.slice.Limit)
+	} else {
+		i.node = i.p.findLast()
+	}
+	return i.fill(true, false)
+}
+
+func (i *dbIter) Seek(key []byte) bool {
+	if i.Released() {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	i.forward = true
+	i.p.mu.RLock()
+	defer i.p.mu.RUnlock()
+	if i.slice != nil && i.slice.Start != nil && i.p.cmp.Compare(key, i.slice.Start) < 0 {
+		key = i.slice.Start
+	}
+	i.node, _ = i.p.findGE(key, false)
+	return i.fill(false, true)
+}
+
+func (i *dbIter) Next() bool {
+	if i.Released() {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	if i.node == 0 {
+		if !i.forward {
+			return i.First()
+		}
+		return false
+	}
+	i.forward = true
+	i.p.mu.RLock()
+	defer i.p.mu.RUnlock()
+	i.node = i.p.nodeData[i.node+nNext]
+	return i.fill(false, true)
+}
+
+func (i *dbIter) Prev() bool {
+	if i.Released() {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	if i.node == 0 {
+		if i.forward {
+			return i.Last()
+		}
+		return false
+	}
+	i.forward = false
+	i.p.mu.RLock()
+	defer i.p.mu.RUnlock()
+	i.node = i.p.findLT(i.key)
+	return i.fill(true, false)
+}
+
+func (i *dbIter) Key() []byte {
+	return i.key
+}
+
+func (i *dbIter) Value() []byte {
+	return i.value
+}
+
+func (i *dbIter) Error() error { return i.err }
+
+func (i *dbIter) Release() {
+	if !i.Released() {
+		i.p = nil
+		i.node = 0
+		i.key = nil
+		i.value = nil
+		i.BasicReleaser.Release()
+	}
+}
+
+const (
+	nKV = iota
+	nKey
+	nVal
+	nHeight
+	nNext
+)
+
+// DB is an in-memory key/value database.
+type DB struct {
+	cmp comparer.BasicComparer
+	rnd *rand.Rand
+
+	mu     sync.RWMutex
+	kvData []byte
+	// Node data:
+	// [0]         : KV offset
+	// [1]         : Key length
+	// [2]         : Value length
+	// [3]         : Height
+	// [3..height] : Next nodes
+	nodeData  []int
+	prevNode  [tMaxHeight]int
+	maxHeight int
+	n         int
+	kvSize    int
+}
+
+func (p *DB) randHeight() (h int) {
+	const branching = 4
+	h = 1
+	for h < tMaxHeight && p.rnd.Int()%branching == 0 {
+		h++
+	}
+	return
+}
+
+// Must hold RW-lock if prev == true, as it use shared prevNode slice.
+func (p *DB) findGE(key []byte, prev bool) (int, bool) {
+	node := 0
+	h := p.maxHeight - 1
+	for {
+		next := p.nodeData[node+nNext+h]
+		cmp := 1
+		if next != 0 {
+			o := p.nodeData[next]
+			cmp = p.cmp.Compare(p.kvData[o:o+p.nodeData[next+nKey]], key)
+		}
+		if cmp < 0 {
+			// Keep searching in this list
+			node = next
+		} else {
+			if prev {
+				p.prevNode[h] = node
+			} else if cmp == 0 {
+				return next, true
+			}
+			if h == 0 {
+				return next, cmp == 0
+			}
+			h--
+		}
+	}
+}
+
+func (p *DB) findLT(key []byte) int {
+	node := 0
+	h := p.maxHeight - 1
+	for {
+		next := p.nodeData[node+nNext+h]
+		o := p.nodeData[next]
+		if next == 0 || p.cmp.Compare(p.kvData[o:o+p.nodeData[next+nKey]], key) >= 0 {
+			if h == 0 {
+				break
+			}
+			h--
+		} else {
+			node = next
+		}
+	}
+	return node
+}
+
+func (p *DB) findLast() int {
+	node := 0
+	h := p.maxHeight - 1
+	for {
+		next := p.nodeData[node+nNext+h]
+		if next == 0 {
+			if h == 0 {
+				break
+			}
+			h--
+		} else {
+			node = next
+		}
+	}
+	return node
+}
+
+// Put sets the value for the given key. It overwrites any previous value
+// for that key; a DB is not a multi-map.
+//
+// It is safe to modify the contents of the arguments after Put returns.
+func (p *DB) Put(key []byte, value []byte) error {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	if node, exact := p.findGE(key, true); exact {
+		kvOffset := len(p.kvData)
+		p.kvData = append(p.kvData, key...)
+		p.kvData = append(p.kvData, value...)
+		p.nodeData[node] = kvOffset
+		m := p.nodeData[node+nVal]
+		p.nodeData[node+nVal] = len(value)
+		p.kvSize += len(value) - m
+		return nil
+	}
+
+	h := p.randHeight()
+	if h > p.maxHeight {
+		for i := p.maxHeight; i < h; i++ {
+			p.prevNode[i] = 0
+		}
+		p.maxHeight = h
+	}
+
+	kvOffset := len(p.kvData)
+	p.kvData = append(p.kvData, key...)
+	p.kvData = append(p.kvData, value...)
+	// Node
+	node := len(p.nodeData)
+	p.nodeData = append(p.nodeData, kvOffset, len(key), len(value), h)
+	for i, n := range p.prevNode[:h] {
+		m := n + nNext + i
+		p.nodeData = append(p.nodeData, p.nodeData[m])
+		p.nodeData[m] = node
+	}
+
+	p.kvSize += len(key) + len(value)
+	p.n++
+	return nil
+}
+
+// Delete deletes the value for the given key. It returns ErrNotFound if
+// the DB does not contain the key.
+//
+// It is safe to modify the contents of the arguments after Delete returns.
+func (p *DB) Delete(key []byte) error {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	node, exact := p.findGE(key, true)
+	if !exact {
+		return ErrNotFound
+	}
+
+	h := p.nodeData[node+nHeight]
+	for i, n := range p.prevNode[:h] {
+		m := n + nNext + i
+		p.nodeData[m] = p.nodeData[p.nodeData[m]+nNext+i]
+	}
+
+	p.kvSize -= p.nodeData[node+nKey] + p.nodeData[node+nVal]
+	p.n--
+	return nil
+}
+
+// Contains returns true if the given key are in the DB.
+//
+// It is safe to modify the contents of the arguments after Contains returns.
+func (p *DB) Contains(key []byte) bool {
+	p.mu.RLock()
+	_, exact := p.findGE(key, false)
+	p.mu.RUnlock()
+	return exact
+}
+
+// Get gets the value for the given key. It returns error.ErrNotFound if the
+// DB does not contain the key.
+//
+// The caller should not modify the contents of the returned slice, but
+// it is safe to modify the contents of the argument after Get returns.
+func (p *DB) Get(key []byte) (value []byte, err error) {
+	p.mu.RLock()
+	if node, exact := p.findGE(key, false); exact {
+		o := p.nodeData[node] + p.nodeData[node+nKey]
+		value = p.kvData[o : o+p.nodeData[node+nVal]]
+	} else {
+		err = ErrNotFound
+	}
+	p.mu.RUnlock()
+	return
+}
+
+// Find finds key/value pair whose key is greater than or equal to the
+// given key. It returns ErrNotFound if the table doesn't contain
+// such pair.
+//
+// The caller should not modify the contents of the returned slice, but
+// it is safe to modify the contents of the argument after Find returns.
+func (p *DB) Find(key []byte) (rkey, value []byte, err error) {
+	p.mu.RLock()
+	if node, _ := p.findGE(key, false); node != 0 {
+		n := p.nodeData[node]
+		m := n + p.nodeData[node+nKey]
+		rkey = p.kvData[n:m]
+		value = p.kvData[m : m+p.nodeData[node+nVal]]
+	} else {
+		err = ErrNotFound
+	}
+	p.mu.RUnlock()
+	return
+}
+
+// NewIterator returns an iterator of the DB.
+// The returned iterator is not safe for concurrent use, but it is safe to use
+// multiple iterators concurrently, with each in a dedicated goroutine.
+// It is also safe to use an iterator concurrently with modifying its
+// underlying DB. However, the resultant key/value pairs are not guaranteed
+// to be a consistent snapshot of the DB at a particular point in time.
+//
+// Slice allows slicing the iterator to only contains keys in the given
+// range. A nil Range.Start is treated as a key before all keys in the
+// DB. And a nil Range.Limit is treated as a key after all keys in
+// the DB.
+//
+// WARNING: Any slice returned by interator (e.g. slice returned by calling
+// Iterator.Key() or Iterator.Key() methods), its content should not be modified
+// unless noted otherwise.
+//
+// The iterator must be released after use, by calling Release method.
+//
+// Also read Iterator documentation of the leveldb/iterator package.
+func (p *DB) NewIterator(slice *util.Range) iterator.Iterator {
+	return &dbIter{p: p, slice: slice}
+}
+
+// Capacity returns keys/values buffer capacity.
+func (p *DB) Capacity() int {
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+	return cap(p.kvData)
+}
+
+// Size returns sum of keys and values length. Note that deleted
+// key/value will not be accounted for, but it will still consume
+// the buffer, since the buffer is append only.
+func (p *DB) Size() int {
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+	return p.kvSize
+}
+
+// Free returns keys/values free buffer before need to grow.
+func (p *DB) Free() int {
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+	return cap(p.kvData) - len(p.kvData)
+}
+
+// Len returns the number of entries in the DB.
+func (p *DB) Len() int {
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+	return p.n
+}
+
+// Reset resets the DB to initial empty state. Allows reuse the buffer.
+func (p *DB) Reset() {
+	p.mu.Lock()
+	p.rnd = rand.New(rand.NewSource(0xdeadbeef))
+	p.maxHeight = 1
+	p.n = 0
+	p.kvSize = 0
+	p.kvData = p.kvData[:0]
+	p.nodeData = p.nodeData[:nNext+tMaxHeight]
+	p.nodeData[nKV] = 0
+	p.nodeData[nKey] = 0
+	p.nodeData[nVal] = 0
+	p.nodeData[nHeight] = tMaxHeight
+	for n := 0; n < tMaxHeight; n++ {
+		p.nodeData[nNext+n] = 0
+		p.prevNode[n] = 0
+	}
+	p.mu.Unlock()
+}
+
+// New creates a new initialized in-memory key/value DB. The capacity
+// is the initial key/value buffer capacity. The capacity is advisory,
+// not enforced.
+//
+// This DB is append-only, deleting an entry would remove entry node but not
+// reclaim KV buffer.
+//
+// The returned DB instance is safe for concurrent use.
+func New(cmp comparer.BasicComparer, capacity int) *DB {
+	p := &DB{
+		cmp:       cmp,
+		rnd:       rand.New(rand.NewSource(0xdeadbeef)),
+		maxHeight: 1,
+		kvData:    make([]byte, 0, capacity),
+		nodeData:  make([]int, 4+tMaxHeight),
+	}
+	p.nodeData[nHeight] = tMaxHeight
+	return p
+}

vendor/github.com/syndtr/goleveldb/leveldb/opt/options.go

@@ -0,0 +1,697 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Package opt provides sets of options used by LevelDB.
+package opt
+
+import (
+	"math"
+
+	"github.com/syndtr/goleveldb/leveldb/cache"
+	"github.com/syndtr/goleveldb/leveldb/comparer"
+	"github.com/syndtr/goleveldb/leveldb/filter"
+)
+
+const (
+	KiB = 1024
+	MiB = KiB * 1024
+	GiB = MiB * 1024
+)
+
+var (
+	DefaultBlockCacher                   = LRUCacher
+	DefaultBlockCacheCapacity            = 8 * MiB
+	DefaultBlockRestartInterval          = 16
+	DefaultBlockSize                     = 4 * KiB
+	DefaultCompactionExpandLimitFactor   = 25
+	DefaultCompactionGPOverlapsFactor    = 10
+	DefaultCompactionL0Trigger           = 4
+	DefaultCompactionSourceLimitFactor   = 1
+	DefaultCompactionTableSize           = 2 * MiB
+	DefaultCompactionTableSizeMultiplier = 1.0
+	DefaultCompactionTotalSize           = 10 * MiB
+	DefaultCompactionTotalSizeMultiplier = 10.0
+	DefaultCompressionType               = SnappyCompression
+	DefaultIteratorSamplingRate          = 1 * MiB
+	DefaultOpenFilesCacher               = LRUCacher
+	DefaultOpenFilesCacheCapacity        = 500
+	DefaultWriteBuffer                   = 4 * MiB
+	DefaultWriteL0PauseTrigger           = 12
+	DefaultWriteL0SlowdownTrigger        = 8
+)
+
+// Cacher is a caching algorithm.
+type Cacher interface {
+	New(capacity int) cache.Cacher
+}
+
+type CacherFunc struct {
+	NewFunc func(capacity int) cache.Cacher
+}
+
+func (f *CacherFunc) New(capacity int) cache.Cacher {
+	if f.NewFunc != nil {
+		return f.NewFunc(capacity)
+	}
+	return nil
+}
+
+func noCacher(int) cache.Cacher { return nil }
+
+var (
+	// LRUCacher is the LRU-cache algorithm.
+	LRUCacher = &CacherFunc{cache.NewLRU}
+
+	// NoCacher is the value to disable caching algorithm.
+	NoCacher = &CacherFunc{}
+)
+
+// Compression is the 'sorted table' block compression algorithm to use.
+type Compression uint
+
+func (c Compression) String() string {
+	switch c {
+	case DefaultCompression:
+		return "default"
+	case NoCompression:
+		return "none"
+	case SnappyCompression:
+		return "snappy"
+	}
+	return "invalid"
+}
+
+const (
+	DefaultCompression Compression = iota
+	NoCompression
+	SnappyCompression
+	nCompression
+)
+
+// Strict is the DB 'strict level'.
+type Strict uint
+
+const (
+	// If present then a corrupted or invalid chunk or block in manifest
+	// journal will cause an error instead of being dropped.
+	// This will prevent database with corrupted manifest to be opened.
+	StrictManifest Strict = 1 << iota
+
+	// If present then journal chunk checksum will be verified.
+	StrictJournalChecksum
+
+	// If present then a corrupted or invalid chunk or block in journal
+	// will cause an error instead of being dropped.
+	// This will prevent database with corrupted journal to be opened.
+	StrictJournal
+
+	// If present then 'sorted table' block checksum will be verified.
+	// This has effect on both 'read operation' and compaction.
+	StrictBlockChecksum
+
+	// If present then a corrupted 'sorted table' will fails compaction.
+	// The database will enter read-only mode.
+	StrictCompaction
+
+	// If present then a corrupted 'sorted table' will halts 'read operation'.
+	StrictReader
+
+	// If present then leveldb.Recover will drop corrupted 'sorted table'.
+	StrictRecovery
+
+	// This only applicable for ReadOptions, if present then this ReadOptions
+	// 'strict level' will override global ones.
+	StrictOverride
+
+	// StrictAll enables all strict flags.
+	StrictAll = StrictManifest | StrictJournalChecksum | StrictJournal | StrictBlockChecksum | StrictCompaction | StrictReader | StrictRecovery
+
+	// DefaultStrict is the default strict flags. Specify any strict flags
+	// will override default strict flags as whole (i.e. not OR'ed).
+	DefaultStrict = StrictJournalChecksum | StrictBlockChecksum | StrictCompaction | StrictReader
+
+	// NoStrict disables all strict flags. Override default strict flags.
+	NoStrict = ^StrictAll
+)
+
+// Options holds the optional parameters for the DB at large.
+type Options struct {
+	// AltFilters defines one or more 'alternative filters'.
+	// 'alternative filters' will be used during reads if a filter block
+	// does not match with the 'effective filter'.
+	//
+	// The default value is nil
+	AltFilters []filter.Filter
+
+	// BlockCacher provides cache algorithm for LevelDB 'sorted table' block caching.
+	// Specify NoCacher to disable caching algorithm.
+	//
+	// The default value is LRUCacher.
+	BlockCacher Cacher
+
+	// BlockCacheCapacity defines the capacity of the 'sorted table' block caching.
+	// Use -1 for zero, this has same effect as specifying NoCacher to BlockCacher.
+	//
+	// The default value is 8MiB.
+	BlockCacheCapacity int
+
+	// BlockCacheEvictRemoved allows enable forced-eviction on cached block belonging
+	// to removed 'sorted table'.
+	//
+	// The default if false.
+	BlockCacheEvictRemoved bool
+
+	// BlockRestartInterval is the number of keys between restart points for
+	// delta encoding of keys.
+	//
+	// The default value is 16.
+	BlockRestartInterval int
+
+	// BlockSize is the minimum uncompressed size in bytes of each 'sorted table'
+	// block.
+	//
+	// The default value is 4KiB.
+	BlockSize int
+
+	// CompactionExpandLimitFactor limits compaction size after expanded.
+	// This will be multiplied by table size limit at compaction target level.
+	//
+	// The default value is 25.
+	CompactionExpandLimitFactor int
+
+	// CompactionGPOverlapsFactor limits overlaps in grandparent (Level + 2) that a
+	// single 'sorted table' generates.
+	// This will be multiplied by table size limit at grandparent level.
+	//
+	// The default value is 10.
+	CompactionGPOverlapsFactor int
+
+	// CompactionL0Trigger defines number of 'sorted table' at level-0 that will
+	// trigger compaction.
+	//
+	// The default value is 4.
+	CompactionL0Trigger int
+
+	// CompactionSourceLimitFactor limits compaction source size. This doesn't apply to
+	// level-0.
+	// This will be multiplied by table size limit at compaction target level.
+	//
+	// The default value is 1.
+	CompactionSourceLimitFactor int
+
+	// CompactionTableSize limits size of 'sorted table' that compaction generates.
+	// The limits for each level will be calculated as:
+	//   CompactionTableSize * (CompactionTableSizeMultiplier ^ Level)
+	// The multiplier for each level can also fine-tuned using CompactionTableSizeMultiplierPerLevel.
+	//
+	// The default value is 2MiB.
+	CompactionTableSize int
+
+	// CompactionTableSizeMultiplier defines multiplier for CompactionTableSize.
+	//
+	// The default value is 1.
+	CompactionTableSizeMultiplier float64
+
+	// CompactionTableSizeMultiplierPerLevel defines per-level multiplier for
+	// CompactionTableSize.
+	// Use zero to skip a level.
+	//
+	// The default value is nil.
+	CompactionTableSizeMultiplierPerLevel []float64
+
+	// CompactionTotalSize limits total size of 'sorted table' for each level.
+	// The limits for each level will be calculated as:
+	//   CompactionTotalSize * (CompactionTotalSizeMultiplier ^ Level)
+	// The multiplier for each level can also fine-tuned using
+	// CompactionTotalSizeMultiplierPerLevel.
+	//
+	// The default value is 10MiB.
+	CompactionTotalSize int
+
+	// CompactionTotalSizeMultiplier defines multiplier for CompactionTotalSize.
+	//
+	// The default value is 10.
+	CompactionTotalSizeMultiplier float64
+
+	// CompactionTotalSizeMultiplierPerLevel defines per-level multiplier for
+	// CompactionTotalSize.
+	// Use zero to skip a level.
+	//
+	// The default value is nil.
+	CompactionTotalSizeMultiplierPerLevel []float64
+
+	// Comparer defines a total ordering over the space of []byte keys: a 'less
+	// than' relationship. The same comparison algorithm must be used for reads
+	// and writes over the lifetime of the DB.
+	//
+	// The default value uses the same ordering as bytes.Compare.
+	Comparer comparer.Comparer
+
+	// Compression defines the 'sorted table' block compression to use.
+	//
+	// The default value (DefaultCompression) uses snappy compression.
+	Compression Compression
+
+	// DisableBufferPool allows disable use of util.BufferPool functionality.
+	//
+	// The default value is false.
+	DisableBufferPool bool
+
+	// DisableBlockCache allows disable use of cache.Cache functionality on
+	// 'sorted table' block.
+	//
+	// The default value is false.
+	DisableBlockCache bool
+
+	// DisableCompactionBackoff allows disable compaction retry backoff.
+	//
+	// The default value is false.
+	DisableCompactionBackoff bool
+
+	// DisableLargeBatchTransaction allows disabling switch-to-transaction mode
+	// on large batch write. If enable batch writes large than WriteBuffer will
+	// use transaction.
+	//
+	// The default is false.
+	DisableLargeBatchTransaction bool
+
+	// ErrorIfExist defines whether an error should returned if the DB already
+	// exist.
+	//
+	// The default value is false.
+	ErrorIfExist bool
+
+	// ErrorIfMissing defines whether an error should returned if the DB is
+	// missing. If false then the database will be created if missing, otherwise
+	// an error will be returned.
+	//
+	// The default value is false.
+	ErrorIfMissing bool
+
+	// Filter defines an 'effective filter' to use. An 'effective filter'
+	// if defined will be used to generate per-table filter block.
+	// The filter name will be stored on disk.
+	// During reads LevelDB will try to find matching filter from
+	// 'effective filter' and 'alternative filters'.
+	//
+	// Filter can be changed after a DB has been created. It is recommended
+	// to put old filter to the 'alternative filters' to mitigate lack of
+	// filter during transition period.
+	//
+	// A filter is used to reduce disk reads when looking for a specific key.
+	//
+	// The default value is nil.
+	Filter filter.Filter
+
+	// IteratorSamplingRate defines approximate gap (in bytes) between read
+	// sampling of an iterator. The samples will be used to determine when
+	// compaction should be triggered.
+	//
+	// The default is 1MiB.
+	IteratorSamplingRate int
+
+	// NoSync allows completely disable fsync.
+	//
+	// The default is false.
+	NoSync bool
+
+	// NoWriteMerge allows disabling write merge.
+	//
+	// The default is false.
+	NoWriteMerge bool
+
+	// OpenFilesCacher provides cache algorithm for open files caching.
+	// Specify NoCacher to disable caching algorithm.
+	//
+	// The default value is LRUCacher.
+	OpenFilesCacher Cacher
+
+	// OpenFilesCacheCapacity defines the capacity of the open files caching.
+	// Use -1 for zero, this has same effect as specifying NoCacher to OpenFilesCacher.
+	//
+	// The default value is 500.
+	OpenFilesCacheCapacity int
+
+	// If true then opens DB in read-only mode.
+	//
+	// The default value is false.
+	ReadOnly bool
+
+	// Strict defines the DB strict level.
+	Strict Strict
+
+	// WriteBuffer defines maximum size of a 'memdb' before flushed to
+	// 'sorted table'. 'memdb' is an in-memory DB backed by an on-disk
+	// unsorted journal.
+	//
+	// LevelDB may held up to two 'memdb' at the same time.
+	//
+	// The default value is 4MiB.
+	WriteBuffer int
+
+	// WriteL0StopTrigger defines number of 'sorted table' at level-0 that will
+	// pause write.
+	//
+	// The default value is 12.
+	WriteL0PauseTrigger int
+
+	// WriteL0SlowdownTrigger defines number of 'sorted table' at level-0 that
+	// will trigger write slowdown.
+	//
+	// The default value is 8.
+	WriteL0SlowdownTrigger int
+}
+
+func (o *Options) GetAltFilters() []filter.Filter {
+	if o == nil {
+		return nil
+	}
+	return o.AltFilters
+}
+
+func (o *Options) GetBlockCacher() Cacher {
+	if o == nil || o.BlockCacher == nil {
+		return DefaultBlockCacher
+	} else if o.BlockCacher == NoCacher {
+		return nil
+	}
+	return o.BlockCacher
+}
+
+func (o *Options) GetBlockCacheCapacity() int {
+	if o == nil || o.BlockCacheCapacity == 0 {
+		return DefaultBlockCacheCapacity
+	} else if o.BlockCacheCapacity < 0 {
+		return 0
+	}
+	return o.BlockCacheCapacity
+}
+
+func (o *Options) GetBlockCacheEvictRemoved() bool {
+	if o == nil {
+		return false
+	}
+	return o.BlockCacheEvictRemoved
+}
+
+func (o *Options) GetBlockRestartInterval() int {
+	if o == nil || o.BlockRestartInterval <= 0 {
+		return DefaultBlockRestartInterval
+	}
+	return o.BlockRestartInterval
+}
+
+func (o *Options) GetBlockSize() int {
+	if o == nil || o.BlockSize <= 0 {
+		return DefaultBlockSize
+	}
+	return o.BlockSize
+}
+
+func (o *Options) GetCompactionExpandLimit(level int) int {
+	factor := DefaultCompactionExpandLimitFactor
+	if o != nil && o.CompactionExpandLimitFactor > 0 {
+		factor = o.CompactionExpandLimitFactor
+	}
+	return o.GetCompactionTableSize(level+1) * factor
+}
+
+func (o *Options) GetCompactionGPOverlaps(level int) int {
+	factor := DefaultCompactionGPOverlapsFactor
+	if o != nil && o.CompactionGPOverlapsFactor > 0 {
+		factor = o.CompactionGPOverlapsFactor
+	}
+	return o.GetCompactionTableSize(level+2) * factor
+}
+
+func (o *Options) GetCompactionL0Trigger() int {
+	if o == nil || o.CompactionL0Trigger == 0 {
+		return DefaultCompactionL0Trigger
+	}
+	return o.CompactionL0Trigger
+}
+
+func (o *Options) GetCompactionSourceLimit(level int) int {
+	factor := DefaultCompactionSourceLimitFactor
+	if o != nil && o.CompactionSourceLimitFactor > 0 {
+		factor = o.CompactionSourceLimitFactor
+	}
+	return o.GetCompactionTableSize(level+1) * factor
+}
+
+func (o *Options) GetCompactionTableSize(level int) int {
+	var (
+		base = DefaultCompactionTableSize
+		mult float64
+	)
+	if o != nil {
+		if o.CompactionTableSize > 0 {
+			base = o.CompactionTableSize
+		}
+		if level < len(o.CompactionTableSizeMultiplierPerLevel) && o.CompactionTableSizeMultiplierPerLevel[level] > 0 {
+			mult = o.CompactionTableSizeMultiplierPerLevel[level]
+		} else if o.CompactionTableSizeMultiplier > 0 {
+			mult = math.Pow(o.CompactionTableSizeMultiplier, float64(level))
+		}
+	}
+	if mult == 0 {
+		mult = math.Pow(DefaultCompactionTableSizeMultiplier, float64(level))
+	}
+	return int(float64(base) * mult)
+}
+
+func (o *Options) GetCompactionTotalSize(level int) int64 {
+	var (
+		base = DefaultCompactionTotalSize
+		mult float64
+	)
+	if o != nil {
+		if o.CompactionTotalSize > 0 {
+			base = o.CompactionTotalSize
+		}
+		if level < len(o.CompactionTotalSizeMultiplierPerLevel) && o.CompactionTotalSizeMultiplierPerLevel[level] > 0 {
+			mult = o.CompactionTotalSizeMultiplierPerLevel[level]
+		} else if o.CompactionTotalSizeMultiplier > 0 {
+			mult = math.Pow(o.CompactionTotalSizeMultiplier, float64(level))
+		}
+	}
+	if mult == 0 {
+		mult = math.Pow(DefaultCompactionTotalSizeMultiplier, float64(level))
+	}
+	return int64(float64(base) * mult)
+}
+
+func (o *Options) GetComparer() comparer.Comparer {
+	if o == nil || o.Comparer == nil {
+		return comparer.DefaultComparer
+	}
+	return o.Comparer
+}
+
+func (o *Options) GetCompression() Compression {
+	if o == nil || o.Compression <= DefaultCompression || o.Compression >= nCompression {
+		return DefaultCompressionType
+	}
+	return o.Compression
+}
+
+func (o *Options) GetDisableBufferPool() bool {
+	if o == nil {
+		return false
+	}
+	return o.DisableBufferPool
+}
+
+func (o *Options) GetDisableBlockCache() bool {
+	if o == nil {
+		return false
+	}
+	return o.DisableBlockCache
+}
+
+func (o *Options) GetDisableCompactionBackoff() bool {
+	if o == nil {
+		return false
+	}
+	return o.DisableCompactionBackoff
+}
+
+func (o *Options) GetDisableLargeBatchTransaction() bool {
+	if o == nil {
+		return false
+	}
+	return o.DisableLargeBatchTransaction
+}
+
+func (o *Options) GetErrorIfExist() bool {
+	if o == nil {
+		return false
+	}
+	return o.ErrorIfExist
+}
+
+func (o *Options) GetErrorIfMissing() bool {
+	if o == nil {
+		return false
+	}
+	return o.ErrorIfMissing
+}
+
+func (o *Options) GetFilter() filter.Filter {
+	if o == nil {
+		return nil
+	}
+	return o.Filter
+}
+
+func (o *Options) GetIteratorSamplingRate() int {
+	if o == nil || o.IteratorSamplingRate <= 0 {
+		return DefaultIteratorSamplingRate
+	}
+	return o.IteratorSamplingRate
+}
+
+func (o *Options) GetNoSync() bool {
+	if o == nil {
+		return false
+	}
+	return o.NoSync
+}
+
+func (o *Options) GetNoWriteMerge() bool {
+	if o == nil {
+		return false
+	}
+	return o.NoWriteMerge
+}
+
+func (o *Options) GetOpenFilesCacher() Cacher {
+	if o == nil || o.OpenFilesCacher == nil {
+		return DefaultOpenFilesCacher
+	}
+	if o.OpenFilesCacher == NoCacher {
+		return nil
+	}
+	return o.OpenFilesCacher
+}
+
+func (o *Options) GetOpenFilesCacheCapacity() int {
+	if o == nil || o.OpenFilesCacheCapacity == 0 {
+		return DefaultOpenFilesCacheCapacity
+	} else if o.OpenFilesCacheCapacity < 0 {
+		return 0
+	}
+	return o.OpenFilesCacheCapacity
+}
+
+func (o *Options) GetReadOnly() bool {
+	if o == nil {
+		return false
+	}
+	return o.ReadOnly
+}
+
+func (o *Options) GetStrict(strict Strict) bool {
+	if o == nil || o.Strict == 0 {
+		return DefaultStrict&strict != 0
+	}
+	return o.Strict&strict != 0
+}
+
+func (o *Options) GetWriteBuffer() int {
+	if o == nil || o.WriteBuffer <= 0 {
+		return DefaultWriteBuffer
+	}
+	return o.WriteBuffer
+}
+
+func (o *Options) GetWriteL0PauseTrigger() int {
+	if o == nil || o.WriteL0PauseTrigger == 0 {
+		return DefaultWriteL0PauseTrigger
+	}
+	return o.WriteL0PauseTrigger
+}
+
+func (o *Options) GetWriteL0SlowdownTrigger() int {
+	if o == nil || o.WriteL0SlowdownTrigger == 0 {
+		return DefaultWriteL0SlowdownTrigger
+	}
+	return o.WriteL0SlowdownTrigger
+}
+
+// ReadOptions holds the optional parameters for 'read operation'. The
+// 'read operation' includes Get, Find and NewIterator.
+type ReadOptions struct {
+	// DontFillCache defines whether block reads for this 'read operation'
+	// should be cached. If false then the block will be cached. This does
+	// not affects already cached block.
+	//
+	// The default value is false.
+	DontFillCache bool
+
+	// Strict will be OR'ed with global DB 'strict level' unless StrictOverride
+	// is present. Currently only StrictReader that has effect here.
+	Strict Strict
+}
+
+func (ro *ReadOptions) GetDontFillCache() bool {
+	if ro == nil {
+		return false
+	}
+	return ro.DontFillCache
+}
+
+func (ro *ReadOptions) GetStrict(strict Strict) bool {
+	if ro == nil {
+		return false
+	}
+	return ro.Strict&strict != 0
+}
+
+// WriteOptions holds the optional parameters for 'write operation'. The
+// 'write operation' includes Write, Put and Delete.
+type WriteOptions struct {
+	// NoWriteMerge allows disabling write merge.
+	//
+	// The default is false.
+	NoWriteMerge bool
+
+	// Sync is whether to sync underlying writes from the OS buffer cache
+	// through to actual disk, if applicable. Setting Sync can result in
+	// slower writes.
+	//
+	// If false, and the machine crashes, then some recent writes may be lost.
+	// Note that if it is just the process that crashes (and the machine does
+	// not) then no writes will be lost.
+	//
+	// In other words, Sync being false has the same semantics as a write
+	// system call. Sync being true means write followed by fsync.
+	//
+	// The default value is false.
+	Sync bool
+}
+
+func (wo *WriteOptions) GetNoWriteMerge() bool {
+	if wo == nil {
+		return false
+	}
+	return wo.NoWriteMerge
+}
+
+func (wo *WriteOptions) GetSync() bool {
+	if wo == nil {
+		return false
+	}
+	return wo.Sync
+}
+
+func GetStrict(o *Options, ro *ReadOptions, strict Strict) bool {
+	if ro.GetStrict(StrictOverride) {
+		return ro.GetStrict(strict)
+	} else {
+		return o.GetStrict(strict) || ro.GetStrict(strict)
+	}
+}

vendor/github.com/syndtr/goleveldb/leveldb/options.go

@@ -0,0 +1,107 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"github.com/syndtr/goleveldb/leveldb/filter"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+)
+
+func dupOptions(o *opt.Options) *opt.Options {
+	newo := &opt.Options{}
+	if o != nil {
+		*newo = *o
+	}
+	if newo.Strict == 0 {
+		newo.Strict = opt.DefaultStrict
+	}
+	return newo
+}
+
+func (s *session) setOptions(o *opt.Options) {
+	no := dupOptions(o)
+	// Alternative filters.
+	if filters := o.GetAltFilters(); len(filters) > 0 {
+		no.AltFilters = make([]filter.Filter, len(filters))
+		for i, filter := range filters {
+			no.AltFilters[i] = &iFilter{filter}
+		}
+	}
+	// Comparer.
+	s.icmp = &iComparer{o.GetComparer()}
+	no.Comparer = s.icmp
+	// Filter.
+	if filter := o.GetFilter(); filter != nil {
+		no.Filter = &iFilter{filter}
+	}
+
+	s.o = &cachedOptions{Options: no}
+	s.o.cache()
+}
+
+const optCachedLevel = 7
+
+type cachedOptions struct {
+	*opt.Options
+
+	compactionExpandLimit []int
+	compactionGPOverlaps  []int
+	compactionSourceLimit []int
+	compactionTableSize   []int
+	compactionTotalSize   []int64
+}
+
+func (co *cachedOptions) cache() {
+	co.compactionExpandLimit = make([]int, optCachedLevel)
+	co.compactionGPOverlaps = make([]int, optCachedLevel)
+	co.compactionSourceLimit = make([]int, optCachedLevel)
+	co.compactionTableSize = make([]int, optCachedLevel)
+	co.compactionTotalSize = make([]int64, optCachedLevel)
+
+	for level := 0; level < optCachedLevel; level++ {
+		co.compactionExpandLimit[level] = co.Options.GetCompactionExpandLimit(level)
+		co.compactionGPOverlaps[level] = co.Options.GetCompactionGPOverlaps(level)
+		co.compactionSourceLimit[level] = co.Options.GetCompactionSourceLimit(level)
+		co.compactionTableSize[level] = co.Options.GetCompactionTableSize(level)
+		co.compactionTotalSize[level] = co.Options.GetCompactionTotalSize(level)
+	}
+}
+
+func (co *cachedOptions) GetCompactionExpandLimit(level int) int {
+	if level < optCachedLevel {
+		return co.compactionExpandLimit[level]
+	}
+	return co.Options.GetCompactionExpandLimit(level)
+}
+
+func (co *cachedOptions) GetCompactionGPOverlaps(level int) int {
+	if level < optCachedLevel {
+		return co.compactionGPOverlaps[level]
+	}
+	return co.Options.GetCompactionGPOverlaps(level)
+}
+
+func (co *cachedOptions) GetCompactionSourceLimit(level int) int {
+	if level < optCachedLevel {
+		return co.compactionSourceLimit[level]
+	}
+	return co.Options.GetCompactionSourceLimit(level)
+}
+
+func (co *cachedOptions) GetCompactionTableSize(level int) int {
+	if level < optCachedLevel {
+		return co.compactionTableSize[level]
+	}
+	return co.Options.GetCompactionTableSize(level)
+}
+
+func (co *cachedOptions) GetCompactionTotalSize(level int) int64 {
+	if level < optCachedLevel {
+		return co.compactionTotalSize[level]
+	}
+	return co.Options.GetCompactionTotalSize(level)
+}

vendor/github.com/syndtr/goleveldb/leveldb/session.go

@@ -0,0 +1,210 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"sync"
+
+	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/journal"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+)
+
+// ErrManifestCorrupted records manifest corruption. This error will be
+// wrapped with errors.ErrCorrupted.
+type ErrManifestCorrupted struct {
+	Field  string
+	Reason string
+}
+
+func (e *ErrManifestCorrupted) Error() string {
+	return fmt.Sprintf("leveldb: manifest corrupted (field '%s'): %s", e.Field, e.Reason)
+}
+
+func newErrManifestCorrupted(fd storage.FileDesc, field, reason string) error {
+	return errors.NewErrCorrupted(fd, &ErrManifestCorrupted{field, reason})
+}
+
+// session represent a persistent database session.
+type session struct {
+	// Need 64-bit alignment.
+	stNextFileNum    int64 // current unused file number
+	stJournalNum     int64 // current journal file number; need external synchronization
+	stPrevJournalNum int64 // prev journal file number; no longer used; for compatibility with older version of leveldb
+	stTempFileNum    int64
+	stSeqNum         uint64 // last mem compacted seq; need external synchronization
+
+	stor     *iStorage
+	storLock storage.Locker
+	o        *cachedOptions
+	icmp     *iComparer
+	tops     *tOps
+	fileRef  map[int64]int
+
+	manifest       *journal.Writer
+	manifestWriter storage.Writer
+	manifestFd     storage.FileDesc
+
+	stCompPtrs []internalKey // compaction pointers; need external synchronization
+	stVersion  *version      // current version
+	vmu        sync.Mutex
+}
+
+// Creates new initialized session instance.
+func newSession(stor storage.Storage, o *opt.Options) (s *session, err error) {
+	if stor == nil {
+		return nil, os.ErrInvalid
+	}
+	storLock, err := stor.Lock()
+	if err != nil {
+		return
+	}
+	s = &session{
+		stor:     newIStorage(stor),
+		storLock: storLock,
+		fileRef:  make(map[int64]int),
+	}
+	s.setOptions(o)
+	s.tops = newTableOps(s)
+	s.setVersion(newVersion(s))
+	s.log("log@legend F·NumFile S·FileSize N·Entry C·BadEntry B·BadBlock Ke·KeyError D·DroppedEntry L·Level Q·SeqNum T·TimeElapsed")
+	return
+}
+
+// Close session.
+func (s *session) close() {
+	s.tops.close()
+	if s.manifest != nil {
+		s.manifest.Close()
+	}
+	if s.manifestWriter != nil {
+		s.manifestWriter.Close()
+	}
+	s.manifest = nil
+	s.manifestWriter = nil
+	s.setVersion(&version{s: s, closing: true})
+}
+
+// Release session lock.
+func (s *session) release() {
+	s.storLock.Unlock()
+}
+
+// Create a new database session; need external synchronization.
+func (s *session) create() error {
+	// create manifest
+	return s.newManifest(nil, nil)
+}
+
+// Recover a database session; need external synchronization.
+func (s *session) recover() (err error) {
+	defer func() {
+		if os.IsNotExist(err) {
+			// Don't return os.ErrNotExist if the underlying storage contains
+			// other files that belong to LevelDB. So the DB won't get trashed.
+			if fds, _ := s.stor.List(storage.TypeAll); len(fds) > 0 {
+				err = &errors.ErrCorrupted{Fd: storage.FileDesc{Type: storage.TypeManifest}, Err: &errors.ErrMissingFiles{}}
+			}
+		}
+	}()
+
+	fd, err := s.stor.GetMeta()
+	if err != nil {
+		return
+	}
+
+	reader, err := s.stor.Open(fd)
+	if err != nil {
+		return
+	}
+	defer reader.Close()
+
+	var (
+		// Options.
+		strict = s.o.GetStrict(opt.StrictManifest)
+
+		jr      = journal.NewReader(reader, dropper{s, fd}, strict, true)
+		rec     = &sessionRecord{}
+		staging = s.stVersion.newStaging()
+	)
+	for {
+		var r io.Reader
+		r, err = jr.Next()
+		if err != nil {
+			if err == io.EOF {
+				err = nil
+				break
+			}
+			return errors.SetFd(err, fd)
+		}
+
+		err = rec.decode(r)
+		if err == nil {
+			// save compact pointers
+			for _, r := range rec.compPtrs {
+				s.setCompPtr(r.level, internalKey(r.ikey))
+			}
+			// commit record to version staging
+			staging.commit(rec)
+		} else {
+			err = errors.SetFd(err, fd)
+			if strict || !errors.IsCorrupted(err) {
+				return
+			}
+			s.logf("manifest error: %v (skipped)", errors.SetFd(err, fd))
+		}
+		rec.resetCompPtrs()
+		rec.resetAddedTables()
+		rec.resetDeletedTables()
+	}
+
+	switch {
+	case !rec.has(recComparer):
+		return newErrManifestCorrupted(fd, "comparer", "missing")
+	case rec.comparer != s.icmp.uName():
+		return newErrManifestCorrupted(fd, "comparer", fmt.Sprintf("mismatch: want '%s', got '%s'", s.icmp.uName(), rec.comparer))
+	case !rec.has(recNextFileNum):
+		return newErrManifestCorrupted(fd, "next-file-num", "missing")
+	case !rec.has(recJournalNum):
+		return newErrManifestCorrupted(fd, "journal-file-num", "missing")
+	case !rec.has(recSeqNum):
+		return newErrManifestCorrupted(fd, "seq-num", "missing")
+	}
+
+	s.manifestFd = fd
+	s.setVersion(staging.finish())
+	s.setNextFileNum(rec.nextFileNum)
+	s.recordCommited(rec)
+	return nil
+}
+
+// Commit session; need external synchronization.
+func (s *session) commit(r *sessionRecord) (err error) {
+	v := s.version()
+	defer v.release()
+
+	// spawn new version based on current version
+	nv := v.spawn(r)
+
+	if s.manifest == nil {
+		// manifest journal writer not yet created, create one
+		err = s.newManifest(r, nv)
+	} else {
+		err = s.flushManifest(r)
+	}
+
+	// finally, apply new version if no error rise
+	if err == nil {
+		s.setVersion(nv)
+	}
+
+	return
+}

vendor/github.com/syndtr/goleveldb/leveldb/session_compaction.go

@@ -0,0 +1,302 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"sync/atomic"
+
+	"github.com/syndtr/goleveldb/leveldb/iterator"
+	"github.com/syndtr/goleveldb/leveldb/memdb"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+)
+
+func (s *session) pickMemdbLevel(umin, umax []byte, maxLevel int) int {
+	v := s.version()
+	defer v.release()
+	return v.pickMemdbLevel(umin, umax, maxLevel)
+}
+
+func (s *session) flushMemdb(rec *sessionRecord, mdb *memdb.DB, maxLevel int) (int, error) {
+	// Create sorted table.
+	iter := mdb.NewIterator(nil)
+	defer iter.Release()
+	t, n, err := s.tops.createFrom(iter)
+	if err != nil {
+		return 0, err
+	}
+
+	// Pick level other than zero can cause compaction issue with large
+	// bulk insert and delete on strictly incrementing key-space. The
+	// problem is that the small deletion markers trapped at lower level,
+	// while key/value entries keep growing at higher level. Since the
+	// key-space is strictly incrementing it will not overlaps with
+	// higher level, thus maximum possible level is always picked, while
+	// overlapping deletion marker pushed into lower level.
+	// See: https://github.com/syndtr/goleveldb/issues/127.
+	flushLevel := s.pickMemdbLevel(t.imin.ukey(), t.imax.ukey(), maxLevel)
+	rec.addTableFile(flushLevel, t)
+
+	s.logf("memdb@flush created L%d@%d N·%d S·%s %q:%q", flushLevel, t.fd.Num, n, shortenb(int(t.size)), t.imin, t.imax)
+	return flushLevel, nil
+}
+
+// Pick a compaction based on current state; need external synchronization.
+func (s *session) pickCompaction() *compaction {
+	v := s.version()
+
+	var sourceLevel int
+	var t0 tFiles
+	if v.cScore >= 1 {
+		sourceLevel = v.cLevel
+		cptr := s.getCompPtr(sourceLevel)
+		tables := v.levels[sourceLevel]
+		for _, t := range tables {
+			if cptr == nil || s.icmp.Compare(t.imax, cptr) > 0 {
+				t0 = append(t0, t)
+				break
+			}
+		}
+		if len(t0) == 0 {
+			t0 = append(t0, tables[0])
+		}
+	} else {
+		if p := atomic.LoadPointer(&v.cSeek); p != nil {
+			ts := (*tSet)(p)
+			sourceLevel = ts.level
+			t0 = append(t0, ts.table)
+		} else {
+			v.release()
+			return nil
+		}
+	}
+
+	return newCompaction(s, v, sourceLevel, t0)
+}
+
+// Create compaction from given level and range; need external synchronization.
+func (s *session) getCompactionRange(sourceLevel int, umin, umax []byte, noLimit bool) *compaction {
+	v := s.version()
+
+	if sourceLevel >= len(v.levels) {
+		v.release()
+		return nil
+	}
+
+	t0 := v.levels[sourceLevel].getOverlaps(nil, s.icmp, umin, umax, sourceLevel == 0)
+	if len(t0) == 0 {
+		v.release()
+		return nil
+	}
+
+	// Avoid compacting too much in one shot in case the range is large.
+	// But we cannot do this for level-0 since level-0 files can overlap
+	// and we must not pick one file and drop another older file if the
+	// two files overlap.
+	if !noLimit && sourceLevel > 0 {
+		limit := int64(v.s.o.GetCompactionSourceLimit(sourceLevel))
+		total := int64(0)
+		for i, t := range t0 {
+			total += t.size
+			if total >= limit {
+				s.logf("table@compaction limiting F·%d -> F·%d", len(t0), i+1)
+				t0 = t0[:i+1]
+				break
+			}
+		}
+	}
+
+	return newCompaction(s, v, sourceLevel, t0)
+}
+
+func newCompaction(s *session, v *version, sourceLevel int, t0 tFiles) *compaction {
+	c := &compaction{
+		s:             s,
+		v:             v,
+		sourceLevel:   sourceLevel,
+		levels:        [2]tFiles{t0, nil},
+		maxGPOverlaps: int64(s.o.GetCompactionGPOverlaps(sourceLevel)),
+		tPtrs:         make([]int, len(v.levels)),
+	}
+	c.expand()
+	c.save()
+	return c
+}
+
+// compaction represent a compaction state.
+type compaction struct {
+	s *session
+	v *version
+
+	sourceLevel   int
+	levels        [2]tFiles
+	maxGPOverlaps int64
+
+	gp                tFiles
+	gpi               int
+	seenKey           bool
+	gpOverlappedBytes int64
+	imin, imax        internalKey
+	tPtrs             []int
+	released          bool
+
+	snapGPI               int
+	snapSeenKey           bool
+	snapGPOverlappedBytes int64
+	snapTPtrs             []int
+}
+
+func (c *compaction) save() {
+	c.snapGPI = c.gpi
+	c.snapSeenKey = c.seenKey
+	c.snapGPOverlappedBytes = c.gpOverlappedBytes
+	c.snapTPtrs = append(c.snapTPtrs[:0], c.tPtrs...)
+}
+
+func (c *compaction) restore() {
+	c.gpi = c.snapGPI
+	c.seenKey = c.snapSeenKey
+	c.gpOverlappedBytes = c.snapGPOverlappedBytes
+	c.tPtrs = append(c.tPtrs[:0], c.snapTPtrs...)
+}
+
+func (c *compaction) release() {
+	if !c.released {
+		c.released = true
+		c.v.release()
+	}
+}
+
+// Expand compacted tables; need external synchronization.
+func (c *compaction) expand() {
+	limit := int64(c.s.o.GetCompactionExpandLimit(c.sourceLevel))
+	vt0 := c.v.levels[c.sourceLevel]
+	vt1 := tFiles{}
+	if level := c.sourceLevel + 1; level < len(c.v.levels) {
+		vt1 = c.v.levels[level]
+	}
+
+	t0, t1 := c.levels[0], c.levels[1]
+	imin, imax := t0.getRange(c.s.icmp)
+	// We expand t0 here just incase ukey hop across tables.
+	t0 = vt0.getOverlaps(t0, c.s.icmp, imin.ukey(), imax.ukey(), c.sourceLevel == 0)
+	if len(t0) != len(c.levels[0]) {
+		imin, imax = t0.getRange(c.s.icmp)
+	}
+	t1 = vt1.getOverlaps(t1, c.s.icmp, imin.ukey(), imax.ukey(), false)
+	// Get entire range covered by compaction.
+	amin, amax := append(t0, t1...).getRange(c.s.icmp)
+
+	// See if we can grow the number of inputs in "sourceLevel" without
+	// changing the number of "sourceLevel+1" files we pick up.
+	if len(t1) > 0 {
+		exp0 := vt0.getOverlaps(nil, c.s.icmp, amin.ukey(), amax.ukey(), c.sourceLevel == 0)
+		if len(exp0) > len(t0) && t1.size()+exp0.size() < limit {
+			xmin, xmax := exp0.getRange(c.s.icmp)
+			exp1 := vt1.getOverlaps(nil, c.s.icmp, xmin.ukey(), xmax.ukey(), false)
+			if len(exp1) == len(t1) {
+				c.s.logf("table@compaction expanding L%d+L%d (F·%d S·%s)+(F·%d S·%s) -> (F·%d S·%s)+(F·%d S·%s)",
+					c.sourceLevel, c.sourceLevel+1, len(t0), shortenb(int(t0.size())), len(t1), shortenb(int(t1.size())),
+					len(exp0), shortenb(int(exp0.size())), len(exp1), shortenb(int(exp1.size())))
+				imin, imax = xmin, xmax
+				t0, t1 = exp0, exp1
+				amin, amax = append(t0, t1...).getRange(c.s.icmp)
+			}
+		}
+	}
+
+	// Compute the set of grandparent files that overlap this compaction
+	// (parent == sourceLevel+1; grandparent == sourceLevel+2)
+	if level := c.sourceLevel + 2; level < len(c.v.levels) {
+		c.gp = c.v.levels[level].getOverlaps(c.gp, c.s.icmp, amin.ukey(), amax.ukey(), false)
+	}
+
+	c.levels[0], c.levels[1] = t0, t1
+	c.imin, c.imax = imin, imax
+}
+
+// Check whether compaction is trivial.
+func (c *compaction) trivial() bool {
+	return len(c.levels[0]) == 1 && len(c.levels[1]) == 0 && c.gp.size() <= c.maxGPOverlaps
+}
+
+func (c *compaction) baseLevelForKey(ukey []byte) bool {
+	for level := c.sourceLevel + 2; level < len(c.v.levels); level++ {
+		tables := c.v.levels[level]
+		for c.tPtrs[level] < len(tables) {
+			t := tables[c.tPtrs[level]]
+			if c.s.icmp.uCompare(ukey, t.imax.ukey()) <= 0 {
+				// We've advanced far enough.
+				if c.s.icmp.uCompare(ukey, t.imin.ukey()) >= 0 {
+					// Key falls in this file's range, so definitely not base level.
+					return false
+				}
+				break
+			}
+			c.tPtrs[level]++
+		}
+	}
+	return true
+}
+
+func (c *compaction) shouldStopBefore(ikey internalKey) bool {
+	for ; c.gpi < len(c.gp); c.gpi++ {
+		gp := c.gp[c.gpi]
+		if c.s.icmp.Compare(ikey, gp.imax) <= 0 {
+			break
+		}
+		if c.seenKey {
+			c.gpOverlappedBytes += gp.size
+		}
+	}
+	c.seenKey = true
+
+	if c.gpOverlappedBytes > c.maxGPOverlaps {
+		// Too much overlap for current output; start new output.
+		c.gpOverlappedBytes = 0
+		return true
+	}
+	return false
+}
+
+// Creates an iterator.
+func (c *compaction) newIterator() iterator.Iterator {
+	// Creates iterator slice.
+	icap := len(c.levels)
+	if c.sourceLevel == 0 {
+		// Special case for level-0.
+		icap = len(c.levels[0]) + 1
+	}
+	its := make([]iterator.Iterator, 0, icap)
+
+	// Options.
+	ro := &opt.ReadOptions{
+		DontFillCache: true,
+		Strict:        opt.StrictOverride,
+	}
+	strict := c.s.o.GetStrict(opt.StrictCompaction)
+	if strict {
+		ro.Strict |= opt.StrictReader
+	}
+
+	for i, tables := range c.levels {
+		if len(tables) == 0 {
+			continue
+		}
+
+		// Level-0 is not sorted and may overlaps each other.
+		if c.sourceLevel+i == 0 {
+			for _, t := range tables {
+				its = append(its, c.s.tops.newIterator(t, nil, ro))
+			}
+		} else {
+			it := iterator.NewIndexedIterator(tables.newIndexIterator(c.s.tops, c.s.icmp, nil, ro), strict)
+			its = append(its, it)
+		}
+	}
+
+	return iterator.NewMergedIterator(its, c.s.icmp, strict)
+}

vendor/github.com/syndtr/goleveldb/leveldb/session_record.go

@@ -0,0 +1,323 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"bufio"
+	"encoding/binary"
+	"io"
+	"strings"
+
+	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+)
+
+type byteReader interface {
+	io.Reader
+	io.ByteReader
+}
+
+// These numbers are written to disk and should not be changed.
+const (
+	recComparer    = 1
+	recJournalNum  = 2
+	recNextFileNum = 3
+	recSeqNum      = 4
+	recCompPtr     = 5
+	recDelTable    = 6
+	recAddTable    = 7
+	// 8 was used for large value refs
+	recPrevJournalNum = 9
+)
+
+type cpRecord struct {
+	level int
+	ikey  internalKey
+}
+
+type atRecord struct {
+	level int
+	num   int64
+	size  int64
+	imin  internalKey
+	imax  internalKey
+}
+
+type dtRecord struct {
+	level int
+	num   int64
+}
+
+type sessionRecord struct {
+	hasRec         int
+	comparer       string
+	journalNum     int64
+	prevJournalNum int64
+	nextFileNum    int64
+	seqNum         uint64
+	compPtrs       []cpRecord
+	addedTables    []atRecord
+	deletedTables  []dtRecord
+
+	scratch [binary.MaxVarintLen64]byte
+	err     error
+}
+
+func (p *sessionRecord) has(rec int) bool {
+	return p.hasRec&(1<<uint(rec)) != 0
+}
+
+func (p *sessionRecord) setComparer(name string) {
+	p.hasRec |= 1 << recComparer
+	p.comparer = name
+}
+
+func (p *sessionRecord) setJournalNum(num int64) {
+	p.hasRec |= 1 << recJournalNum
+	p.journalNum = num
+}
+
+func (p *sessionRecord) setPrevJournalNum(num int64) {
+	p.hasRec |= 1 << recPrevJournalNum
+	p.prevJournalNum = num
+}
+
+func (p *sessionRecord) setNextFileNum(num int64) {
+	p.hasRec |= 1 << recNextFileNum
+	p.nextFileNum = num
+}
+
+func (p *sessionRecord) setSeqNum(num uint64) {
+	p.hasRec |= 1 << recSeqNum
+	p.seqNum = num
+}
+
+func (p *sessionRecord) addCompPtr(level int, ikey internalKey) {
+	p.hasRec |= 1 << recCompPtr
+	p.compPtrs = append(p.compPtrs, cpRecord{level, ikey})
+}
+
+func (p *sessionRecord) resetCompPtrs() {
+	p.hasRec &= ^(1 << recCompPtr)
+	p.compPtrs = p.compPtrs[:0]
+}
+
+func (p *sessionRecord) addTable(level int, num, size int64, imin, imax internalKey) {
+	p.hasRec |= 1 << recAddTable
+	p.addedTables = append(p.addedTables, atRecord{level, num, size, imin, imax})
+}
+
+func (p *sessionRecord) addTableFile(level int, t *tFile) {
+	p.addTable(level, t.fd.Num, t.size, t.imin, t.imax)
+}
+
+func (p *sessionRecord) resetAddedTables() {
+	p.hasRec &= ^(1 << recAddTable)
+	p.addedTables = p.addedTables[:0]
+}
+
+func (p *sessionRecord) delTable(level int, num int64) {
+	p.hasRec |= 1 << recDelTable
+	p.deletedTables = append(p.deletedTables, dtRecord{level, num})
+}
+
+func (p *sessionRecord) resetDeletedTables() {
+	p.hasRec &= ^(1 << recDelTable)
+	p.deletedTables = p.deletedTables[:0]
+}
+
+func (p *sessionRecord) putUvarint(w io.Writer, x uint64) {
+	if p.err != nil {
+		return
+	}
+	n := binary.PutUvarint(p.scratch[:], x)
+	_, p.err = w.Write(p.scratch[:n])
+}
+
+func (p *sessionRecord) putVarint(w io.Writer, x int64) {
+	if x < 0 {
+		panic("invalid negative value")
+	}
+	p.putUvarint(w, uint64(x))
+}
+
+func (p *sessionRecord) putBytes(w io.Writer, x []byte) {
+	if p.err != nil {
+		return
+	}
+	p.putUvarint(w, uint64(len(x)))
+	if p.err != nil {
+		return
+	}
+	_, p.err = w.Write(x)
+}
+
+func (p *sessionRecord) encode(w io.Writer) error {
+	p.err = nil
+	if p.has(recComparer) {
+		p.putUvarint(w, recComparer)
+		p.putBytes(w, []byte(p.comparer))
+	}
+	if p.has(recJournalNum) {
+		p.putUvarint(w, recJournalNum)
+		p.putVarint(w, p.journalNum)
+	}
+	if p.has(recNextFileNum) {
+		p.putUvarint(w, recNextFileNum)
+		p.putVarint(w, p.nextFileNum)
+	}
+	if p.has(recSeqNum) {
+		p.putUvarint(w, recSeqNum)
+		p.putUvarint(w, p.seqNum)
+	}
+	for _, r := range p.compPtrs {
+		p.putUvarint(w, recCompPtr)
+		p.putUvarint(w, uint64(r.level))
+		p.putBytes(w, r.ikey)
+	}
+	for _, r := range p.deletedTables {
+		p.putUvarint(w, recDelTable)
+		p.putUvarint(w, uint64(r.level))
+		p.putVarint(w, r.num)
+	}
+	for _, r := range p.addedTables {
+		p.putUvarint(w, recAddTable)
+		p.putUvarint(w, uint64(r.level))
+		p.putVarint(w, r.num)
+		p.putVarint(w, r.size)
+		p.putBytes(w, r.imin)
+		p.putBytes(w, r.imax)
+	}
+	return p.err
+}
+
+func (p *sessionRecord) readUvarintMayEOF(field string, r io.ByteReader, mayEOF bool) uint64 {
+	if p.err != nil {
+		return 0
+	}
+	x, err := binary.ReadUvarint(r)
+	if err != nil {
+		if err == io.ErrUnexpectedEOF || (mayEOF == false && err == io.EOF) {
+			p.err = errors.NewErrCorrupted(storage.FileDesc{}, &ErrManifestCorrupted{field, "short read"})
+		} else if strings.HasPrefix(err.Error(), "binary:") {
+			p.err = errors.NewErrCorrupted(storage.FileDesc{}, &ErrManifestCorrupted{field, err.Error()})
+		} else {
+			p.err = err
+		}
+		return 0
+	}
+	return x
+}
+
+func (p *sessionRecord) readUvarint(field string, r io.ByteReader) uint64 {
+	return p.readUvarintMayEOF(field, r, false)
+}
+
+func (p *sessionRecord) readVarint(field string, r io.ByteReader) int64 {
+	x := int64(p.readUvarintMayEOF(field, r, false))
+	if x < 0 {
+		p.err = errors.NewErrCorrupted(storage.FileDesc{}, &ErrManifestCorrupted{field, "invalid negative value"})
+	}
+	return x
+}
+
+func (p *sessionRecord) readBytes(field string, r byteReader) []byte {
+	if p.err != nil {
+		return nil
+	}
+	n := p.readUvarint(field, r)
+	if p.err != nil {
+		return nil
+	}
+	x := make([]byte, n)
+	_, p.err = io.ReadFull(r, x)
+	if p.err != nil {
+		if p.err == io.ErrUnexpectedEOF {
+			p.err = errors.NewErrCorrupted(storage.FileDesc{}, &ErrManifestCorrupted{field, "short read"})
+		}
+		return nil
+	}
+	return x
+}
+
+func (p *sessionRecord) readLevel(field string, r io.ByteReader) int {
+	if p.err != nil {
+		return 0
+	}
+	x := p.readUvarint(field, r)
+	if p.err != nil {
+		return 0
+	}
+	return int(x)
+}
+
+func (p *sessionRecord) decode(r io.Reader) error {
+	br, ok := r.(byteReader)
+	if !ok {
+		br = bufio.NewReader(r)
+	}
+	p.err = nil
+	for p.err == nil {
+		rec := p.readUvarintMayEOF("field-header", br, true)
+		if p.err != nil {
+			if p.err == io.EOF {
+				return nil
+			}
+			return p.err
+		}
+		switch rec {
+		case recComparer:
+			x := p.readBytes("comparer", br)
+			if p.err == nil {
+				p.setComparer(string(x))
+			}
+		case recJournalNum:
+			x := p.readVarint("journal-num", br)
+			if p.err == nil {
+				p.setJournalNum(x)
+			}
+		case recPrevJournalNum:
+			x := p.readVarint("prev-journal-num", br)
+			if p.err == nil {
+				p.setPrevJournalNum(x)
+			}
+		case recNextFileNum:
+			x := p.readVarint("next-file-num", br)
+			if p.err == nil {
+				p.setNextFileNum(x)
+			}
+		case recSeqNum:
+			x := p.readUvarint("seq-num", br)
+			if p.err == nil {
+				p.setSeqNum(x)
+			}
+		case recCompPtr:
+			level := p.readLevel("comp-ptr.level", br)
+			ikey := p.readBytes("comp-ptr.ikey", br)
+			if p.err == nil {
+				p.addCompPtr(level, internalKey(ikey))
+			}
+		case recAddTable:
+			level := p.readLevel("add-table.level", br)
+			num := p.readVarint("add-table.num", br)
+			size := p.readVarint("add-table.size", br)
+			imin := p.readBytes("add-table.imin", br)
+			imax := p.readBytes("add-table.imax", br)
+			if p.err == nil {
+				p.addTable(level, num, size, imin, imax)
+			}
+		case recDelTable:
+			level := p.readLevel("del-table.level", br)
+			num := p.readVarint("del-table.num", br)
+			if p.err == nil {
+				p.delTable(level, num)
+			}
+		}
+	}
+
+	return p.err
+}

vendor/github.com/syndtr/goleveldb/leveldb/session_util.go

@@ -0,0 +1,271 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"fmt"
+	"sync/atomic"
+
+	"github.com/syndtr/goleveldb/leveldb/journal"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+)
+
+// Logging.
+
+type dropper struct {
+	s  *session
+	fd storage.FileDesc
+}
+
+func (d dropper) Drop(err error) {
+	if e, ok := err.(*journal.ErrCorrupted); ok {
+		d.s.logf("journal@drop %s-%d S·%s %q", d.fd.Type, d.fd.Num, shortenb(e.Size), e.Reason)
+	} else {
+		d.s.logf("journal@drop %s-%d %q", d.fd.Type, d.fd.Num, err)
+	}
+}
+
+func (s *session) log(v ...interface{})                 { s.stor.Log(fmt.Sprint(v...)) }
+func (s *session) logf(format string, v ...interface{}) { s.stor.Log(fmt.Sprintf(format, v...)) }
+
+// File utils.
+
+func (s *session) newTemp() storage.FileDesc {
+	num := atomic.AddInt64(&s.stTempFileNum, 1) - 1
+	return storage.FileDesc{Type: storage.TypeTemp, Num: num}
+}
+
+func (s *session) addFileRef(fd storage.FileDesc, ref int) int {
+	ref += s.fileRef[fd.Num]
+	if ref > 0 {
+		s.fileRef[fd.Num] = ref
+	} else if ref == 0 {
+		delete(s.fileRef, fd.Num)
+	} else {
+		panic(fmt.Sprintf("negative ref: %v", fd))
+	}
+	return ref
+}
+
+// Session state.
+
+// Get current version. This will incr version ref, must call
+// version.release (exactly once) after use.
+func (s *session) version() *version {
+	s.vmu.Lock()
+	defer s.vmu.Unlock()
+	s.stVersion.incref()
+	return s.stVersion
+}
+
+func (s *session) tLen(level int) int {
+	s.vmu.Lock()
+	defer s.vmu.Unlock()
+	return s.stVersion.tLen(level)
+}
+
+// Set current version to v.
+func (s *session) setVersion(v *version) {
+	s.vmu.Lock()
+	defer s.vmu.Unlock()
+	// Hold by session. It is important to call this first before releasing
+	// current version, otherwise the still used files might get released.
+	v.incref()
+	if s.stVersion != nil {
+		// Release current version.
+		s.stVersion.releaseNB()
+	}
+	s.stVersion = v
+}
+
+// Get current unused file number.
+func (s *session) nextFileNum() int64 {
+	return atomic.LoadInt64(&s.stNextFileNum)
+}
+
+// Set current unused file number to num.
+func (s *session) setNextFileNum(num int64) {
+	atomic.StoreInt64(&s.stNextFileNum, num)
+}
+
+// Mark file number as used.
+func (s *session) markFileNum(num int64) {
+	nextFileNum := num + 1
+	for {
+		old, x := s.stNextFileNum, nextFileNum
+		if old > x {
+			x = old
+		}
+		if atomic.CompareAndSwapInt64(&s.stNextFileNum, old, x) {
+			break
+		}
+	}
+}
+
+// Allocate a file number.
+func (s *session) allocFileNum() int64 {
+	return atomic.AddInt64(&s.stNextFileNum, 1) - 1
+}
+
+// Reuse given file number.
+func (s *session) reuseFileNum(num int64) {
+	for {
+		old, x := s.stNextFileNum, num
+		if old != x+1 {
+			x = old
+		}
+		if atomic.CompareAndSwapInt64(&s.stNextFileNum, old, x) {
+			break
+		}
+	}
+}
+
+// Set compaction ptr at given level; need external synchronization.
+func (s *session) setCompPtr(level int, ik internalKey) {
+	if level >= len(s.stCompPtrs) {
+		newCompPtrs := make([]internalKey, level+1)
+		copy(newCompPtrs, s.stCompPtrs)
+		s.stCompPtrs = newCompPtrs
+	}
+	s.stCompPtrs[level] = append(internalKey{}, ik...)
+}
+
+// Get compaction ptr at given level; need external synchronization.
+func (s *session) getCompPtr(level int) internalKey {
+	if level >= len(s.stCompPtrs) {
+		return nil
+	}
+	return s.stCompPtrs[level]
+}
+
+// Manifest related utils.
+
+// Fill given session record obj with current states; need external
+// synchronization.
+func (s *session) fillRecord(r *sessionRecord, snapshot bool) {
+	r.setNextFileNum(s.nextFileNum())
+
+	if snapshot {
+		if !r.has(recJournalNum) {
+			r.setJournalNum(s.stJournalNum)
+		}
+
+		if !r.has(recSeqNum) {
+			r.setSeqNum(s.stSeqNum)
+		}
+
+		for level, ik := range s.stCompPtrs {
+			if ik != nil {
+				r.addCompPtr(level, ik)
+			}
+		}
+
+		r.setComparer(s.icmp.uName())
+	}
+}
+
+// Mark if record has been committed, this will update session state;
+// need external synchronization.
+func (s *session) recordCommited(rec *sessionRecord) {
+	if rec.has(recJournalNum) {
+		s.stJournalNum = rec.journalNum
+	}
+
+	if rec.has(recPrevJournalNum) {
+		s.stPrevJournalNum = rec.prevJournalNum
+	}
+
+	if rec.has(recSeqNum) {
+		s.stSeqNum = rec.seqNum
+	}
+
+	for _, r := range rec.compPtrs {
+		s.setCompPtr(r.level, internalKey(r.ikey))
+	}
+}
+
+// Create a new manifest file; need external synchronization.
+func (s *session) newManifest(rec *sessionRecord, v *version) (err error) {
+	fd := storage.FileDesc{Type: storage.TypeManifest, Num: s.allocFileNum()}
+	writer, err := s.stor.Create(fd)
+	if err != nil {
+		return
+	}
+	jw := journal.NewWriter(writer)
+
+	if v == nil {
+		v = s.version()
+		defer v.release()
+	}
+	if rec == nil {
+		rec = &sessionRecord{}
+	}
+	s.fillRecord(rec, true)
+	v.fillRecord(rec)
+
+	defer func() {
+		if err == nil {
+			s.recordCommited(rec)
+			if s.manifest != nil {
+				s.manifest.Close()
+			}
+			if s.manifestWriter != nil {
+				s.manifestWriter.Close()
+			}
+			if !s.manifestFd.Zero() {
+				s.stor.Remove(s.manifestFd)
+			}
+			s.manifestFd = fd
+			s.manifestWriter = writer
+			s.manifest = jw
+		} else {
+			writer.Close()
+			s.stor.Remove(fd)
+			s.reuseFileNum(fd.Num)
+		}
+	}()
+
+	w, err := jw.Next()
+	if err != nil {
+		return
+	}
+	err = rec.encode(w)
+	if err != nil {
+		return
+	}
+	err = jw.Flush()
+	if err != nil {
+		return
+	}
+	err = s.stor.SetMeta(fd)
+	return
+}
+
+// Flush record to disk.
+func (s *session) flushManifest(rec *sessionRecord) (err error) {
+	s.fillRecord(rec, false)
+	w, err := s.manifest.Next()
+	if err != nil {
+		return
+	}
+	err = rec.encode(w)
+	if err != nil {
+		return
+	}
+	err = s.manifest.Flush()
+	if err != nil {
+		return
+	}
+	if !s.o.GetNoSync() {
+		err = s.manifestWriter.Sync()
+		if err != nil {
+			return
+		}
+	}
+	s.recordCommited(rec)
+	return
+}

vendor/github.com/syndtr/goleveldb/leveldb/storage.go

@@ -0,0 +1,63 @@
+package leveldb
+
+import (
+	"github.com/syndtr/goleveldb/leveldb/storage"
+	"sync/atomic"
+)
+
+type iStorage struct {
+	storage.Storage
+	read  uint64
+	write uint64
+}
+
+func (c *iStorage) Open(fd storage.FileDesc) (storage.Reader, error) {
+	r, err := c.Storage.Open(fd)
+	return &iStorageReader{r, c}, err
+}
+
+func (c *iStorage) Create(fd storage.FileDesc) (storage.Writer, error) {
+	w, err := c.Storage.Create(fd)
+	return &iStorageWriter{w, c}, err
+}
+
+func (c *iStorage) reads() uint64 {
+	return atomic.LoadUint64(&c.read)
+}
+
+func (c *iStorage) writes() uint64 {
+	return atomic.LoadUint64(&c.write)
+}
+
+// newIStorage returns the given storage wrapped by iStorage.
+func newIStorage(s storage.Storage) *iStorage {
+	return &iStorage{s, 0, 0}
+}
+
+type iStorageReader struct {
+	storage.Reader
+	c *iStorage
+}
+
+func (r *iStorageReader) Read(p []byte) (n int, err error) {
+	n, err = r.Reader.Read(p)
+	atomic.AddUint64(&r.c.read, uint64(n))
+	return n, err
+}
+
+func (r *iStorageReader) ReadAt(p []byte, off int64) (n int, err error) {
+	n, err = r.Reader.ReadAt(p, off)
+	atomic.AddUint64(&r.c.read, uint64(n))
+	return n, err
+}
+
+type iStorageWriter struct {
+	storage.Writer
+	c *iStorage
+}
+
+func (w *iStorageWriter) Write(p []byte) (n int, err error) {
+	n, err = w.Writer.Write(p)
+	atomic.AddUint64(&w.c.write, uint64(n))
+	return n, err
+}

vendor/github.com/syndtr/goleveldb/leveldb/storage/file_storage.go

@@ -0,0 +1,671 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reservefs.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package storage
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"runtime"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+)
+
+var (
+	errFileOpen = errors.New("leveldb/storage: file still open")
+	errReadOnly = errors.New("leveldb/storage: storage is read-only")
+)
+
+type fileLock interface {
+	release() error
+}
+
+type fileStorageLock struct {
+	fs *fileStorage
+}
+
+func (lock *fileStorageLock) Unlock() {
+	if lock.fs != nil {
+		lock.fs.mu.Lock()
+		defer lock.fs.mu.Unlock()
+		if lock.fs.slock == lock {
+			lock.fs.slock = nil
+		}
+	}
+}
+
+type int64Slice []int64
+
+func (p int64Slice) Len() int           { return len(p) }
+func (p int64Slice) Less(i, j int) bool { return p[i] < p[j] }
+func (p int64Slice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
+
+func writeFileSynced(filename string, data []byte, perm os.FileMode) error {
+	f, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, perm)
+	if err != nil {
+		return err
+	}
+	n, err := f.Write(data)
+	if err == nil && n < len(data) {
+		err = io.ErrShortWrite
+	}
+	if err1 := f.Sync(); err == nil {
+		err = err1
+	}
+	if err1 := f.Close(); err == nil {
+		err = err1
+	}
+	return err
+}
+
+const logSizeThreshold = 1024 * 1024 // 1 MiB
+
+// fileStorage is a file-system backed storage.
+type fileStorage struct {
+	path     string
+	readOnly bool
+
+	mu      sync.Mutex
+	flock   fileLock
+	slock   *fileStorageLock
+	logw    *os.File
+	logSize int64
+	buf     []byte
+	// Opened file counter; if open < 0 means closed.
+	open int
+	day  int
+}
+
+// OpenFile returns a new filesystem-backed storage implementation with the given
+// path. This also acquire a file lock, so any subsequent attempt to open the
+// same path will fail.
+//
+// The storage must be closed after use, by calling Close method.
+func OpenFile(path string, readOnly bool) (Storage, error) {
+	if fi, err := os.Stat(path); err == nil {
+		if !fi.IsDir() {
+			return nil, fmt.Errorf("leveldb/storage: open %s: not a directory", path)
+		}
+	} else if os.IsNotExist(err) && !readOnly {
+		if err := os.MkdirAll(path, 0755); err != nil {
+			return nil, err
+		}
+	} else {
+		return nil, err
+	}
+
+	flock, err := newFileLock(filepath.Join(path, "LOCK"), readOnly)
+	if err != nil {
+		return nil, err
+	}
+
+	defer func() {
+		if err != nil {
+			flock.release()
+		}
+	}()
+
+	var (
+		logw    *os.File
+		logSize int64
+	)
+	if !readOnly {
+		logw, err = os.OpenFile(filepath.Join(path, "LOG"), os.O_WRONLY|os.O_CREATE, 0644)
+		if err != nil {
+			return nil, err
+		}
+		logSize, err = logw.Seek(0, os.SEEK_END)
+		if err != nil {
+			logw.Close()
+			return nil, err
+		}
+	}
+
+	fs := &fileStorage{
+		path:     path,
+		readOnly: readOnly,
+		flock:    flock,
+		logw:     logw,
+		logSize:  logSize,
+	}
+	runtime.SetFinalizer(fs, (*fileStorage).Close)
+	return fs, nil
+}
+
+func (fs *fileStorage) Lock() (Locker, error) {
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+	if fs.open < 0 {
+		return nil, ErrClosed
+	}
+	if fs.readOnly {
+		return &fileStorageLock{}, nil
+	}
+	if fs.slock != nil {
+		return nil, ErrLocked
+	}
+	fs.slock = &fileStorageLock{fs: fs}
+	return fs.slock, nil
+}
+
+func itoa(buf []byte, i int, wid int) []byte {
+	u := uint(i)
+	if u == 0 && wid <= 1 {
+		return append(buf, '0')
+	}
+
+	// Assemble decimal in reverse order.
+	var b [32]byte
+	bp := len(b)
+	for ; u > 0 || wid > 0; u /= 10 {
+		bp--
+		wid--
+		b[bp] = byte(u%10) + '0'
+	}
+	return append(buf, b[bp:]...)
+}
+
+func (fs *fileStorage) printDay(t time.Time) {
+	if fs.day == t.Day() {
+		return
+	}
+	fs.day = t.Day()
+	fs.logw.Write([]byte("=============== " + t.Format("Jan 2, 2006 (MST)") + " ===============\n"))
+}
+
+func (fs *fileStorage) doLog(t time.Time, str string) {
+	if fs.logSize > logSizeThreshold {
+		// Rotate log file.
+		fs.logw.Close()
+		fs.logw = nil
+		fs.logSize = 0
+		rename(filepath.Join(fs.path, "LOG"), filepath.Join(fs.path, "LOG.old"))
+	}
+	if fs.logw == nil {
+		var err error
+		fs.logw, err = os.OpenFile(filepath.Join(fs.path, "LOG"), os.O_WRONLY|os.O_CREATE, 0644)
+		if err != nil {
+			return
+		}
+		// Force printDay on new log file.
+		fs.day = 0
+	}
+	fs.printDay(t)
+	hour, min, sec := t.Clock()
+	msec := t.Nanosecond() / 1e3
+	// time
+	fs.buf = itoa(fs.buf[:0], hour, 2)
+	fs.buf = append(fs.buf, ':')
+	fs.buf = itoa(fs.buf, min, 2)
+	fs.buf = append(fs.buf, ':')
+	fs.buf = itoa(fs.buf, sec, 2)
+	fs.buf = append(fs.buf, '.')
+	fs.buf = itoa(fs.buf, msec, 6)
+	fs.buf = append(fs.buf, ' ')
+	// write
+	fs.buf = append(fs.buf, []byte(str)...)
+	fs.buf = append(fs.buf, '\n')
+	n, _ := fs.logw.Write(fs.buf)
+	fs.logSize += int64(n)
+}
+
+func (fs *fileStorage) Log(str string) {
+	if !fs.readOnly {
+		t := time.Now()
+		fs.mu.Lock()
+		defer fs.mu.Unlock()
+		if fs.open < 0 {
+			return
+		}
+		fs.doLog(t, str)
+	}
+}
+
+func (fs *fileStorage) log(str string) {
+	if !fs.readOnly {
+		fs.doLog(time.Now(), str)
+	}
+}
+
+func (fs *fileStorage) setMeta(fd FileDesc) error {
+	content := fsGenName(fd) + "\n"
+	// Check and backup old CURRENT file.
+	currentPath := filepath.Join(fs.path, "CURRENT")
+	if _, err := os.Stat(currentPath); err == nil {
+		b, err := ioutil.ReadFile(currentPath)
+		if err != nil {
+			fs.log(fmt.Sprintf("backup CURRENT: %v", err))
+			return err
+		}
+		if string(b) == content {
+			// Content not changed, do nothing.
+			return nil
+		}
+		if err := writeFileSynced(currentPath+".bak", b, 0644); err != nil {
+			fs.log(fmt.Sprintf("backup CURRENT: %v", err))
+			return err
+		}
+	} else if !os.IsNotExist(err) {
+		return err
+	}
+	path := fmt.Sprintf("%s.%d", filepath.Join(fs.path, "CURRENT"), fd.Num)
+	if err := writeFileSynced(path, []byte(content), 0644); err != nil {
+		fs.log(fmt.Sprintf("create CURRENT.%d: %v", fd.Num, err))
+		return err
+	}
+	// Replace CURRENT file.
+	if err := rename(path, currentPath); err != nil {
+		fs.log(fmt.Sprintf("rename CURRENT.%d: %v", fd.Num, err))
+		return err
+	}
+	// Sync root directory.
+	if err := syncDir(fs.path); err != nil {
+		fs.log(fmt.Sprintf("syncDir: %v", err))
+		return err
+	}
+	return nil
+}
+
+func (fs *fileStorage) SetMeta(fd FileDesc) error {
+	if !FileDescOk(fd) {
+		return ErrInvalidFile
+	}
+	if fs.readOnly {
+		return errReadOnly
+	}
+
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+	if fs.open < 0 {
+		return ErrClosed
+	}
+	return fs.setMeta(fd)
+}
+
+func (fs *fileStorage) GetMeta() (FileDesc, error) {
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+	if fs.open < 0 {
+		return FileDesc{}, ErrClosed
+	}
+	dir, err := os.Open(fs.path)
+	if err != nil {
+		return FileDesc{}, err
+	}
+	names, err := dir.Readdirnames(0)
+	// Close the dir first before checking for Readdirnames error.
+	if ce := dir.Close(); ce != nil {
+		fs.log(fmt.Sprintf("close dir: %v", ce))
+	}
+	if err != nil {
+		return FileDesc{}, err
+	}
+	// Try this in order:
+	// - CURRENT.[0-9]+ ('pending rename' file, descending order)
+	// - CURRENT
+	// - CURRENT.bak
+	//
+	// Skip corrupted file or file that point to a missing target file.
+	type currentFile struct {
+		name string
+		fd   FileDesc
+	}
+	tryCurrent := func(name string) (*currentFile, error) {
+		b, err := ioutil.ReadFile(filepath.Join(fs.path, name))
+		if err != nil {
+			if os.IsNotExist(err) {
+				err = os.ErrNotExist
+			}
+			return nil, err
+		}
+		var fd FileDesc
+		if len(b) < 1 || b[len(b)-1] != '\n' || !fsParseNamePtr(string(b[:len(b)-1]), &fd) {
+			fs.log(fmt.Sprintf("%s: corrupted content: %q", name, b))
+			err := &ErrCorrupted{
+				Err: errors.New("leveldb/storage: corrupted or incomplete CURRENT file"),
+			}
+			return nil, err
+		}
+		if _, err := os.Stat(filepath.Join(fs.path, fsGenName(fd))); err != nil {
+			if os.IsNotExist(err) {
+				fs.log(fmt.Sprintf("%s: missing target file: %s", name, fd))
+				err = os.ErrNotExist
+			}
+			return nil, err
+		}
+		return &currentFile{name: name, fd: fd}, nil
+	}
+	tryCurrents := func(names []string) (*currentFile, error) {
+		var (
+			cur *currentFile
+			// Last corruption error.
+			lastCerr error
+		)
+		for _, name := range names {
+			var err error
+			cur, err = tryCurrent(name)
+			if err == nil {
+				break
+			} else if err == os.ErrNotExist {
+				// Fallback to the next file.
+			} else if isCorrupted(err) {
+				lastCerr = err
+				// Fallback to the next file.
+			} else {
+				// In case the error is due to permission, etc.
+				return nil, err
+			}
+		}
+		if cur == nil {
+			err := os.ErrNotExist
+			if lastCerr != nil {
+				err = lastCerr
+			}
+			return nil, err
+		}
+		return cur, nil
+	}
+
+	// Try 'pending rename' files.
+	var nums []int64
+	for _, name := range names {
+		if strings.HasPrefix(name, "CURRENT.") && name != "CURRENT.bak" {
+			i, err := strconv.ParseInt(name[8:], 10, 64)
+			if err == nil {
+				nums = append(nums, i)
+			}
+		}
+	}
+	var (
+		pendCur   *currentFile
+		pendErr   = os.ErrNotExist
+		pendNames []string
+	)
+	if len(nums) > 0 {
+		sort.Sort(sort.Reverse(int64Slice(nums)))
+		pendNames = make([]string, len(nums))
+		for i, num := range nums {
+			pendNames[i] = fmt.Sprintf("CURRENT.%d", num)
+		}
+		pendCur, pendErr = tryCurrents(pendNames)
+		if pendErr != nil && pendErr != os.ErrNotExist && !isCorrupted(pendErr) {
+			return FileDesc{}, pendErr
+		}
+	}
+
+	// Try CURRENT and CURRENT.bak.
+	curCur, curErr := tryCurrents([]string{"CURRENT", "CURRENT.bak"})
+	if curErr != nil && curErr != os.ErrNotExist && !isCorrupted(curErr) {
+		return FileDesc{}, curErr
+	}
+
+	// pendCur takes precedence, but guards against obsolete pendCur.
+	if pendCur != nil && (curCur == nil || pendCur.fd.Num > curCur.fd.Num) {
+		curCur = pendCur
+	}
+
+	if curCur != nil {
+		// Restore CURRENT file to proper state.
+		if !fs.readOnly && (curCur.name != "CURRENT" || len(pendNames) != 0) {
+			// Ignore setMeta errors, however don't delete obsolete files if we
+			// catch error.
+			if err := fs.setMeta(curCur.fd); err == nil {
+				// Remove 'pending rename' files.
+				for _, name := range pendNames {
+					if err := os.Remove(filepath.Join(fs.path, name)); err != nil {
+						fs.log(fmt.Sprintf("remove %s: %v", name, err))
+					}
+				}
+			}
+		}
+		return curCur.fd, nil
+	}
+
+	// Nothing found.
+	if isCorrupted(pendErr) {
+		return FileDesc{}, pendErr
+	}
+	return FileDesc{}, curErr
+}
+
+func (fs *fileStorage) List(ft FileType) (fds []FileDesc, err error) {
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+	if fs.open < 0 {
+		return nil, ErrClosed
+	}
+	dir, err := os.Open(fs.path)
+	if err != nil {
+		return
+	}
+	names, err := dir.Readdirnames(0)
+	// Close the dir first before checking for Readdirnames error.
+	if cerr := dir.Close(); cerr != nil {
+		fs.log(fmt.Sprintf("close dir: %v", cerr))
+	}
+	if err == nil {
+		for _, name := range names {
+			if fd, ok := fsParseName(name); ok && fd.Type&ft != 0 {
+				fds = append(fds, fd)
+			}
+		}
+	}
+	return
+}
+
+func (fs *fileStorage) Open(fd FileDesc) (Reader, error) {
+	if !FileDescOk(fd) {
+		return nil, ErrInvalidFile
+	}
+
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+	if fs.open < 0 {
+		return nil, ErrClosed
+	}
+	of, err := os.OpenFile(filepath.Join(fs.path, fsGenName(fd)), os.O_RDONLY, 0)
+	if err != nil {
+		if fsHasOldName(fd) && os.IsNotExist(err) {
+			of, err = os.OpenFile(filepath.Join(fs.path, fsGenOldName(fd)), os.O_RDONLY, 0)
+			if err == nil {
+				goto ok
+			}
+		}
+		return nil, err
+	}
+ok:
+	fs.open++
+	return &fileWrap{File: of, fs: fs, fd: fd}, nil
+}
+
+func (fs *fileStorage) Create(fd FileDesc) (Writer, error) {
+	if !FileDescOk(fd) {
+		return nil, ErrInvalidFile
+	}
+	if fs.readOnly {
+		return nil, errReadOnly
+	}
+
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+	if fs.open < 0 {
+		return nil, ErrClosed
+	}
+	of, err := os.OpenFile(filepath.Join(fs.path, fsGenName(fd)), os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
+	if err != nil {
+		return nil, err
+	}
+	fs.open++
+	return &fileWrap{File: of, fs: fs, fd: fd}, nil
+}
+
+func (fs *fileStorage) Remove(fd FileDesc) error {
+	if !FileDescOk(fd) {
+		return ErrInvalidFile
+	}
+	if fs.readOnly {
+		return errReadOnly
+	}
+
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+	if fs.open < 0 {
+		return ErrClosed
+	}
+	err := os.Remove(filepath.Join(fs.path, fsGenName(fd)))
+	if err != nil {
+		if fsHasOldName(fd) && os.IsNotExist(err) {
+			if e1 := os.Remove(filepath.Join(fs.path, fsGenOldName(fd))); !os.IsNotExist(e1) {
+				fs.log(fmt.Sprintf("remove %s: %v (old name)", fd, err))
+				err = e1
+			}
+		} else {
+			fs.log(fmt.Sprintf("remove %s: %v", fd, err))
+		}
+	}
+	return err
+}
+
+func (fs *fileStorage) Rename(oldfd, newfd FileDesc) error {
+	if !FileDescOk(oldfd) || !FileDescOk(newfd) {
+		return ErrInvalidFile
+	}
+	if oldfd == newfd {
+		return nil
+	}
+	if fs.readOnly {
+		return errReadOnly
+	}
+
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+	if fs.open < 0 {
+		return ErrClosed
+	}
+	return rename(filepath.Join(fs.path, fsGenName(oldfd)), filepath.Join(fs.path, fsGenName(newfd)))
+}
+
+func (fs *fileStorage) Close() error {
+	fs.mu.Lock()
+	defer fs.mu.Unlock()
+	if fs.open < 0 {
+		return ErrClosed
+	}
+	// Clear the finalizer.
+	runtime.SetFinalizer(fs, nil)
+
+	if fs.open > 0 {
+		fs.log(fmt.Sprintf("close: warning, %d files still open", fs.open))
+	}
+	fs.open = -1
+	if fs.logw != nil {
+		fs.logw.Close()
+	}
+	return fs.flock.release()
+}
+
+type fileWrap struct {
+	*os.File
+	fs     *fileStorage
+	fd     FileDesc
+	closed bool
+}
+
+func (fw *fileWrap) Sync() error {
+	if err := fw.File.Sync(); err != nil {
+		return err
+	}
+	if fw.fd.Type == TypeManifest {
+		// Also sync parent directory if file type is manifest.
+		// See: https://code.google.com/p/leveldb/issues/detail?id=190.
+		if err := syncDir(fw.fs.path); err != nil {
+			fw.fs.log(fmt.Sprintf("syncDir: %v", err))
+			return err
+		}
+	}
+	return nil
+}
+
+func (fw *fileWrap) Close() error {
+	fw.fs.mu.Lock()
+	defer fw.fs.mu.Unlock()
+	if fw.closed {
+		return ErrClosed
+	}
+	fw.closed = true
+	fw.fs.open--
+	err := fw.File.Close()
+	if err != nil {
+		fw.fs.log(fmt.Sprintf("close %s: %v", fw.fd, err))
+	}
+	return err
+}
+
+func fsGenName(fd FileDesc) string {
+	switch fd.Type {
+	case TypeManifest:
+		return fmt.Sprintf("MANIFEST-%06d", fd.Num)
+	case TypeJournal:
+		return fmt.Sprintf("%06d.log", fd.Num)
+	case TypeTable:
+		return fmt.Sprintf("%06d.ldb", fd.Num)
+	case TypeTemp:
+		return fmt.Sprintf("%06d.tmp", fd.Num)
+	default:
+		panic("invalid file type")
+	}
+}
+
+func fsHasOldName(fd FileDesc) bool {
+	return fd.Type == TypeTable
+}
+
+func fsGenOldName(fd FileDesc) string {
+	switch fd.Type {
+	case TypeTable:
+		return fmt.Sprintf("%06d.sst", fd.Num)
+	}
+	return fsGenName(fd)
+}
+
+func fsParseName(name string) (fd FileDesc, ok bool) {
+	var tail string
+	_, err := fmt.Sscanf(name, "%d.%s", &fd.Num, &tail)
+	if err == nil {
+		switch tail {
+		case "log":
+			fd.Type = TypeJournal
+		case "ldb", "sst":
+			fd.Type = TypeTable
+		case "tmp":
+			fd.Type = TypeTemp
+		default:
+			return
+		}
+		return fd, true
+	}
+	n, _ := fmt.Sscanf(name, "MANIFEST-%d%s", &fd.Num, &tail)
+	if n == 1 {
+		fd.Type = TypeManifest
+		return fd, true
+	}
+	return
+}
+
+func fsParseNamePtr(name string, fd *FileDesc) bool {
+	_fd, ok := fsParseName(name)
+	if fd != nil {
+		*fd = _fd
+	}
+	return ok
+}

vendor/github.com/syndtr/goleveldb/leveldb/storage/file_storage_nacl.go

@@ -0,0 +1,34 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// +build nacl
+
+package storage
+
+import (
+	"os"
+	"syscall"
+)
+
+func newFileLock(path string, readOnly bool) (fl fileLock, err error) {
+	return nil, syscall.ENOTSUP
+}
+
+func setFileLock(f *os.File, readOnly, lock bool) error {
+	return syscall.ENOTSUP
+}
+
+func rename(oldpath, newpath string) error {
+	return syscall.ENOTSUP
+}
+
+func isErrInvalid(err error) bool {
+	return false
+}
+
+func syncDir(name string) error {
+	return syscall.ENOTSUP
+}

vendor/github.com/syndtr/goleveldb/leveldb/storage/file_storage_plan9.go

@@ -0,0 +1,63 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package storage
+
+import (
+	"os"
+)
+
+type plan9FileLock struct {
+	f *os.File
+}
+
+func (fl *plan9FileLock) release() error {
+	return fl.f.Close()
+}
+
+func newFileLock(path string, readOnly bool) (fl fileLock, err error) {
+	var (
+		flag int
+		perm os.FileMode
+	)
+	if readOnly {
+		flag = os.O_RDONLY
+	} else {
+		flag = os.O_RDWR
+		perm = os.ModeExclusive
+	}
+	f, err := os.OpenFile(path, flag, perm)
+	if os.IsNotExist(err) {
+		f, err = os.OpenFile(path, flag|os.O_CREATE, perm|0644)
+	}
+	if err != nil {
+		return
+	}
+	fl = &plan9FileLock{f: f}
+	return
+}
+
+func rename(oldpath, newpath string) error {
+	if _, err := os.Stat(newpath); err == nil {
+		if err := os.Remove(newpath); err != nil {
+			return err
+		}
+	}
+
+	return os.Rename(oldpath, newpath)
+}
+
+func syncDir(name string) error {
+	f, err := os.Open(name)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	if err := f.Sync(); err != nil {
+		return err
+	}
+	return nil
+}

vendor/github.com/syndtr/goleveldb/leveldb/storage/file_storage_solaris.go

@@ -0,0 +1,81 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// +build solaris
+
+package storage
+
+import (
+	"os"
+	"syscall"
+)
+
+type unixFileLock struct {
+	f *os.File
+}
+
+func (fl *unixFileLock) release() error {
+	if err := setFileLock(fl.f, false, false); err != nil {
+		return err
+	}
+	return fl.f.Close()
+}
+
+func newFileLock(path string, readOnly bool) (fl fileLock, err error) {
+	var flag int
+	if readOnly {
+		flag = os.O_RDONLY
+	} else {
+		flag = os.O_RDWR
+	}
+	f, err := os.OpenFile(path, flag, 0)
+	if os.IsNotExist(err) {
+		f, err = os.OpenFile(path, flag|os.O_CREATE, 0644)
+	}
+	if err != nil {
+		return
+	}
+	err = setFileLock(f, readOnly, true)
+	if err != nil {
+		f.Close()
+		return
+	}
+	fl = &unixFileLock{f: f}
+	return
+}
+
+func setFileLock(f *os.File, readOnly, lock bool) error {
+	flock := syscall.Flock_t{
+		Type:   syscall.F_UNLCK,
+		Start:  0,
+		Len:    0,
+		Whence: 1,
+	}
+	if lock {
+		if readOnly {
+			flock.Type = syscall.F_RDLCK
+		} else {
+			flock.Type = syscall.F_WRLCK
+		}
+	}
+	return syscall.FcntlFlock(f.Fd(), syscall.F_SETLK, &flock)
+}
+
+func rename(oldpath, newpath string) error {
+	return os.Rename(oldpath, newpath)
+}
+
+func syncDir(name string) error {
+	f, err := os.Open(name)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	if err := f.Sync(); err != nil {
+		return err
+	}
+	return nil
+}

vendor/github.com/syndtr/goleveldb/leveldb/storage/file_storage_unix.go

@@ -0,0 +1,98 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// +build darwin dragonfly freebsd linux netbsd openbsd
+
+package storage
+
+import (
+	"os"
+	"syscall"
+)
+
+type unixFileLock struct {
+	f *os.File
+}
+
+func (fl *unixFileLock) release() error {
+	if err := setFileLock(fl.f, false, false); err != nil {
+		return err
+	}
+	return fl.f.Close()
+}
+
+func newFileLock(path string, readOnly bool) (fl fileLock, err error) {
+	var flag int
+	if readOnly {
+		flag = os.O_RDONLY
+	} else {
+		flag = os.O_RDWR
+	}
+	f, err := os.OpenFile(path, flag, 0)
+	if os.IsNotExist(err) {
+		f, err = os.OpenFile(path, flag|os.O_CREATE, 0644)
+	}
+	if err != nil {
+		return
+	}
+	err = setFileLock(f, readOnly, true)
+	if err != nil {
+		f.Close()
+		return
+	}
+	fl = &unixFileLock{f: f}
+	return
+}
+
+func setFileLock(f *os.File, readOnly, lock bool) error {
+	how := syscall.LOCK_UN
+	if lock {
+		if readOnly {
+			how = syscall.LOCK_SH
+		} else {
+			how = syscall.LOCK_EX
+		}
+	}
+	return syscall.Flock(int(f.Fd()), how|syscall.LOCK_NB)
+}
+
+func rename(oldpath, newpath string) error {
+	return os.Rename(oldpath, newpath)
+}
+
+func isErrInvalid(err error) bool {
+	if err == os.ErrInvalid {
+		return true
+	}
+	// Go < 1.8
+	if syserr, ok := err.(*os.SyscallError); ok && syserr.Err == syscall.EINVAL {
+		return true
+	}
+	// Go >= 1.8 returns *os.PathError instead
+	if patherr, ok := err.(*os.PathError); ok && patherr.Err == syscall.EINVAL {
+		return true
+	}
+	return false
+}
+
+func syncDir(name string) error {
+	// As per fsync manpage, Linux seems to expect fsync on directory, however
+	// some system don't support this, so we will ignore syscall.EINVAL.
+	//
+	// From fsync(2):
+	//   Calling fsync() does not necessarily ensure that the entry in the
+	//   directory containing the file has also reached disk. For that an
+	//   explicit fsync() on a file descriptor for the directory is also needed.
+	f, err := os.Open(name)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	if err := f.Sync(); err != nil && !isErrInvalid(err) {
+		return err
+	}
+	return nil
+}

vendor/github.com/syndtr/goleveldb/leveldb/storage/file_storage_windows.go

@@ -0,0 +1,78 @@
+// Copyright (c) 2013, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package storage
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+var (
+	modkernel32 = syscall.NewLazyDLL("kernel32.dll")
+
+	procMoveFileExW = modkernel32.NewProc("MoveFileExW")
+)
+
+const (
+	_MOVEFILE_REPLACE_EXISTING = 1
+)
+
+type windowsFileLock struct {
+	fd syscall.Handle
+}
+
+func (fl *windowsFileLock) release() error {
+	return syscall.Close(fl.fd)
+}
+
+func newFileLock(path string, readOnly bool) (fl fileLock, err error) {
+	pathp, err := syscall.UTF16PtrFromString(path)
+	if err != nil {
+		return
+	}
+	var access, shareMode uint32
+	if readOnly {
+		access = syscall.GENERIC_READ
+		shareMode = syscall.FILE_SHARE_READ
+	} else {
+		access = syscall.GENERIC_READ | syscall.GENERIC_WRITE
+	}
+	fd, err := syscall.CreateFile(pathp, access, shareMode, nil, syscall.OPEN_EXISTING, syscall.FILE_ATTRIBUTE_NORMAL, 0)
+	if err == syscall.ERROR_FILE_NOT_FOUND {
+		fd, err = syscall.CreateFile(pathp, access, shareMode, nil, syscall.OPEN_ALWAYS, syscall.FILE_ATTRIBUTE_NORMAL, 0)
+	}
+	if err != nil {
+		return
+	}
+	fl = &windowsFileLock{fd: fd}
+	return
+}
+
+func moveFileEx(from *uint16, to *uint16, flags uint32) error {
+	r1, _, e1 := syscall.Syscall(procMoveFileExW.Addr(), 3, uintptr(unsafe.Pointer(from)), uintptr(unsafe.Pointer(to)), uintptr(flags))
+	if r1 == 0 {
+		if e1 != 0 {
+			return error(e1)
+		}
+		return syscall.EINVAL
+	}
+	return nil
+}
+
+func rename(oldpath, newpath string) error {
+	from, err := syscall.UTF16PtrFromString(oldpath)
+	if err != nil {
+		return err
+	}
+	to, err := syscall.UTF16PtrFromString(newpath)
+	if err != nil {
+		return err
+	}
+	return moveFileEx(from, to, _MOVEFILE_REPLACE_EXISTING)
+}
+
+func syncDir(name string) error { return nil }

vendor/github.com/syndtr/goleveldb/leveldb/storage/mem_storage.go

@@ -0,0 +1,222 @@
+// Copyright (c) 2013, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package storage
+
+import (
+	"bytes"
+	"os"
+	"sync"
+)
+
+const typeShift = 4
+
+// Verify at compile-time that typeShift is large enough to cover all FileType
+// values by confirming that 0 == 0.
+var _ [0]struct{} = [TypeAll >> typeShift]struct{}{}
+
+type memStorageLock struct {
+	ms *memStorage
+}
+
+func (lock *memStorageLock) Unlock() {
+	ms := lock.ms
+	ms.mu.Lock()
+	defer ms.mu.Unlock()
+	if ms.slock == lock {
+		ms.slock = nil
+	}
+	return
+}
+
+// memStorage is a memory-backed storage.
+type memStorage struct {
+	mu    sync.Mutex
+	slock *memStorageLock
+	files map[uint64]*memFile
+	meta  FileDesc
+}
+
+// NewMemStorage returns a new memory-backed storage implementation.
+func NewMemStorage() Storage {
+	return &memStorage{
+		files: make(map[uint64]*memFile),
+	}
+}
+
+func (ms *memStorage) Lock() (Locker, error) {
+	ms.mu.Lock()
+	defer ms.mu.Unlock()
+	if ms.slock != nil {
+		return nil, ErrLocked
+	}
+	ms.slock = &memStorageLock{ms: ms}
+	return ms.slock, nil
+}
+
+func (*memStorage) Log(str string) {}
+
+func (ms *memStorage) SetMeta(fd FileDesc) error {
+	if !FileDescOk(fd) {
+		return ErrInvalidFile
+	}
+
+	ms.mu.Lock()
+	ms.meta = fd
+	ms.mu.Unlock()
+	return nil
+}
+
+func (ms *memStorage) GetMeta() (FileDesc, error) {
+	ms.mu.Lock()
+	defer ms.mu.Unlock()
+	if ms.meta.Zero() {
+		return FileDesc{}, os.ErrNotExist
+	}
+	return ms.meta, nil
+}
+
+func (ms *memStorage) List(ft FileType) ([]FileDesc, error) {
+	ms.mu.Lock()
+	var fds []FileDesc
+	for x := range ms.files {
+		fd := unpackFile(x)
+		if fd.Type&ft != 0 {
+			fds = append(fds, fd)
+		}
+	}
+	ms.mu.Unlock()
+	return fds, nil
+}
+
+func (ms *memStorage) Open(fd FileDesc) (Reader, error) {
+	if !FileDescOk(fd) {
+		return nil, ErrInvalidFile
+	}
+
+	ms.mu.Lock()
+	defer ms.mu.Unlock()
+	if m, exist := ms.files[packFile(fd)]; exist {
+		if m.open {
+			return nil, errFileOpen
+		}
+		m.open = true
+		return &memReader{Reader: bytes.NewReader(m.Bytes()), ms: ms, m: m}, nil
+	}
+	return nil, os.ErrNotExist
+}
+
+func (ms *memStorage) Create(fd FileDesc) (Writer, error) {
+	if !FileDescOk(fd) {
+		return nil, ErrInvalidFile
+	}
+
+	x := packFile(fd)
+	ms.mu.Lock()
+	defer ms.mu.Unlock()
+	m, exist := ms.files[x]
+	if exist {
+		if m.open {
+			return nil, errFileOpen
+		}
+		m.Reset()
+	} else {
+		m = &memFile{}
+		ms.files[x] = m
+	}
+	m.open = true
+	return &memWriter{memFile: m, ms: ms}, nil
+}
+
+func (ms *memStorage) Remove(fd FileDesc) error {
+	if !FileDescOk(fd) {
+		return ErrInvalidFile
+	}
+
+	x := packFile(fd)
+	ms.mu.Lock()
+	defer ms.mu.Unlock()
+	if _, exist := ms.files[x]; exist {
+		delete(ms.files, x)
+		return nil
+	}
+	return os.ErrNotExist
+}
+
+func (ms *memStorage) Rename(oldfd, newfd FileDesc) error {
+	if !FileDescOk(oldfd) || !FileDescOk(newfd) {
+		return ErrInvalidFile
+	}
+	if oldfd == newfd {
+		return nil
+	}
+
+	oldx := packFile(oldfd)
+	newx := packFile(newfd)
+	ms.mu.Lock()
+	defer ms.mu.Unlock()
+	oldm, exist := ms.files[oldx]
+	if !exist {
+		return os.ErrNotExist
+	}
+	newm, exist := ms.files[newx]
+	if (exist && newm.open) || oldm.open {
+		return errFileOpen
+	}
+	delete(ms.files, oldx)
+	ms.files[newx] = oldm
+	return nil
+}
+
+func (*memStorage) Close() error { return nil }
+
+type memFile struct {
+	bytes.Buffer
+	open bool
+}
+
+type memReader struct {
+	*bytes.Reader
+	ms     *memStorage
+	m      *memFile
+	closed bool
+}
+
+func (mr *memReader) Close() error {
+	mr.ms.mu.Lock()
+	defer mr.ms.mu.Unlock()
+	if mr.closed {
+		return ErrClosed
+	}
+	mr.m.open = false
+	return nil
+}
+
+type memWriter struct {
+	*memFile
+	ms     *memStorage
+	closed bool
+}
+
+func (*memWriter) Sync() error { return nil }
+
+func (mw *memWriter) Close() error {
+	mw.ms.mu.Lock()
+	defer mw.ms.mu.Unlock()
+	if mw.closed {
+		return ErrClosed
+	}
+	mw.memFile.open = false
+	return nil
+}
+
+func packFile(fd FileDesc) uint64 {
+	return uint64(fd.Num)<<typeShift | uint64(fd.Type)
+}
+
+func unpackFile(x uint64) FileDesc {
+	return FileDesc{FileType(x) & TypeAll, int64(x >> typeShift)}
+}

vendor/github.com/syndtr/goleveldb/leveldb/storage/storage.go

@@ -0,0 +1,187 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Package storage provides storage abstraction for LevelDB.
+package storage
+
+import (
+	"errors"
+	"fmt"
+	"io"
+)
+
+// FileType represent a file type.
+type FileType int
+
+// File types.
+const (
+	TypeManifest FileType = 1 << iota
+	TypeJournal
+	TypeTable
+	TypeTemp
+
+	TypeAll = TypeManifest | TypeJournal | TypeTable | TypeTemp
+)
+
+func (t FileType) String() string {
+	switch t {
+	case TypeManifest:
+		return "manifest"
+	case TypeJournal:
+		return "journal"
+	case TypeTable:
+		return "table"
+	case TypeTemp:
+		return "temp"
+	}
+	return fmt.Sprintf("<unknown:%d>", t)
+}
+
+// Common error.
+var (
+	ErrInvalidFile = errors.New("leveldb/storage: invalid file for argument")
+	ErrLocked      = errors.New("leveldb/storage: already locked")
+	ErrClosed      = errors.New("leveldb/storage: closed")
+)
+
+// ErrCorrupted is the type that wraps errors that indicate corruption of
+// a file. Package storage has its own type instead of using
+// errors.ErrCorrupted to prevent circular import.
+type ErrCorrupted struct {
+	Fd  FileDesc
+	Err error
+}
+
+func isCorrupted(err error) bool {
+	switch err.(type) {
+	case *ErrCorrupted:
+		return true
+	}
+	return false
+}
+
+func (e *ErrCorrupted) Error() string {
+	if !e.Fd.Zero() {
+		return fmt.Sprintf("%v [file=%v]", e.Err, e.Fd)
+	}
+	return e.Err.Error()
+}
+
+// Syncer is the interface that wraps basic Sync method.
+type Syncer interface {
+	// Sync commits the current contents of the file to stable storage.
+	Sync() error
+}
+
+// Reader is the interface that groups the basic Read, Seek, ReadAt and Close
+// methods.
+type Reader interface {
+	io.ReadSeeker
+	io.ReaderAt
+	io.Closer
+}
+
+// Writer is the interface that groups the basic Write, Sync and Close
+// methods.
+type Writer interface {
+	io.WriteCloser
+	Syncer
+}
+
+// Locker is the interface that wraps Unlock method.
+type Locker interface {
+	Unlock()
+}
+
+// FileDesc is a 'file descriptor'.
+type FileDesc struct {
+	Type FileType
+	Num  int64
+}
+
+func (fd FileDesc) String() string {
+	switch fd.Type {
+	case TypeManifest:
+		return fmt.Sprintf("MANIFEST-%06d", fd.Num)
+	case TypeJournal:
+		return fmt.Sprintf("%06d.log", fd.Num)
+	case TypeTable:
+		return fmt.Sprintf("%06d.ldb", fd.Num)
+	case TypeTemp:
+		return fmt.Sprintf("%06d.tmp", fd.Num)
+	default:
+		return fmt.Sprintf("%#x-%d", fd.Type, fd.Num)
+	}
+}
+
+// Zero returns true if fd == (FileDesc{}).
+func (fd FileDesc) Zero() bool {
+	return fd == (FileDesc{})
+}
+
+// FileDescOk returns true if fd is a valid 'file descriptor'.
+func FileDescOk(fd FileDesc) bool {
+	switch fd.Type {
+	case TypeManifest:
+	case TypeJournal:
+	case TypeTable:
+	case TypeTemp:
+	default:
+		return false
+	}
+	return fd.Num >= 0
+}
+
+// Storage is the storage. A storage instance must be safe for concurrent use.
+type Storage interface {
+	// Lock locks the storage. Any subsequent attempt to call Lock will fail
+	// until the last lock released.
+	// Caller should call Unlock method after use.
+	Lock() (Locker, error)
+
+	// Log logs a string. This is used for logging.
+	// An implementation may write to a file, stdout or simply do nothing.
+	Log(str string)
+
+	// SetMeta store 'file descriptor' that can later be acquired using GetMeta
+	// method. The 'file descriptor' should point to a valid file.
+	// SetMeta should be implemented in such way that changes should happen
+	// atomically.
+	SetMeta(fd FileDesc) error
+
+	// GetMeta returns 'file descriptor' stored in meta. The 'file descriptor'
+	// can be updated using SetMeta method.
+	// Returns os.ErrNotExist if meta doesn't store any 'file descriptor', or
+	// 'file descriptor' point to nonexistent file.
+	GetMeta() (FileDesc, error)
+
+	// List returns file descriptors that match the given file types.
+	// The file types may be OR'ed together.
+	List(ft FileType) ([]FileDesc, error)
+
+	// Open opens file with the given 'file descriptor' read-only.
+	// Returns os.ErrNotExist error if the file does not exist.
+	// Returns ErrClosed if the underlying storage is closed.
+	Open(fd FileDesc) (Reader, error)
+
+	// Create creates file with the given 'file descriptor', truncate if already
+	// exist and opens write-only.
+	// Returns ErrClosed if the underlying storage is closed.
+	Create(fd FileDesc) (Writer, error)
+
+	// Remove removes file with the given 'file descriptor'.
+	// Returns ErrClosed if the underlying storage is closed.
+	Remove(fd FileDesc) error
+
+	// Rename renames file from oldfd to newfd.
+	// Returns ErrClosed if the underlying storage is closed.
+	Rename(oldfd, newfd FileDesc) error
+
+	// Close closes the storage.
+	// It is valid to call Close multiple times. Other methods should not be
+	// called after the storage has been closed.
+	Close() error
+}

vendor/github.com/syndtr/goleveldb/leveldb/table.go

@@ -0,0 +1,531 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"fmt"
+	"sort"
+	"sync/atomic"
+
+	"github.com/syndtr/goleveldb/leveldb/cache"
+	"github.com/syndtr/goleveldb/leveldb/iterator"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+	"github.com/syndtr/goleveldb/leveldb/table"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+// tFile holds basic information about a table.
+type tFile struct {
+	fd         storage.FileDesc
+	seekLeft   int32
+	size       int64
+	imin, imax internalKey
+}
+
+// Returns true if given key is after largest key of this table.
+func (t *tFile) after(icmp *iComparer, ukey []byte) bool {
+	return ukey != nil && icmp.uCompare(ukey, t.imax.ukey()) > 0
+}
+
+// Returns true if given key is before smallest key of this table.
+func (t *tFile) before(icmp *iComparer, ukey []byte) bool {
+	return ukey != nil && icmp.uCompare(ukey, t.imin.ukey()) < 0
+}
+
+// Returns true if given key range overlaps with this table key range.
+func (t *tFile) overlaps(icmp *iComparer, umin, umax []byte) bool {
+	return !t.after(icmp, umin) && !t.before(icmp, umax)
+}
+
+// Cosumes one seek and return current seeks left.
+func (t *tFile) consumeSeek() int32 {
+	return atomic.AddInt32(&t.seekLeft, -1)
+}
+
+// Creates new tFile.
+func newTableFile(fd storage.FileDesc, size int64, imin, imax internalKey) *tFile {
+	f := &tFile{
+		fd:   fd,
+		size: size,
+		imin: imin,
+		imax: imax,
+	}
+
+	// We arrange to automatically compact this file after
+	// a certain number of seeks.  Let's assume:
+	//   (1) One seek costs 10ms
+	//   (2) Writing or reading 1MB costs 10ms (100MB/s)
+	//   (3) A compaction of 1MB does 25MB of IO:
+	//         1MB read from this level
+	//         10-12MB read from next level (boundaries may be misaligned)
+	//         10-12MB written to next level
+	// This implies that 25 seeks cost the same as the compaction
+	// of 1MB of data.  I.e., one seek costs approximately the
+	// same as the compaction of 40KB of data.  We are a little
+	// conservative and allow approximately one seek for every 16KB
+	// of data before triggering a compaction.
+	f.seekLeft = int32(size / 16384)
+	if f.seekLeft < 100 {
+		f.seekLeft = 100
+	}
+
+	return f
+}
+
+func tableFileFromRecord(r atRecord) *tFile {
+	return newTableFile(storage.FileDesc{Type: storage.TypeTable, Num: r.num}, r.size, r.imin, r.imax)
+}
+
+// tFiles hold multiple tFile.
+type tFiles []*tFile
+
+func (tf tFiles) Len() int      { return len(tf) }
+func (tf tFiles) Swap(i, j int) { tf[i], tf[j] = tf[j], tf[i] }
+
+func (tf tFiles) nums() string {
+	x := "[ "
+	for i, f := range tf {
+		if i != 0 {
+			x += ", "
+		}
+		x += fmt.Sprint(f.fd.Num)
+	}
+	x += " ]"
+	return x
+}
+
+// Returns true if i smallest key is less than j.
+// This used for sort by key in ascending order.
+func (tf tFiles) lessByKey(icmp *iComparer, i, j int) bool {
+	a, b := tf[i], tf[j]
+	n := icmp.Compare(a.imin, b.imin)
+	if n == 0 {
+		return a.fd.Num < b.fd.Num
+	}
+	return n < 0
+}
+
+// Returns true if i file number is greater than j.
+// This used for sort by file number in descending order.
+func (tf tFiles) lessByNum(i, j int) bool {
+	return tf[i].fd.Num > tf[j].fd.Num
+}
+
+// Sorts tables by key in ascending order.
+func (tf tFiles) sortByKey(icmp *iComparer) {
+	sort.Sort(&tFilesSortByKey{tFiles: tf, icmp: icmp})
+}
+
+// Sorts tables by file number in descending order.
+func (tf tFiles) sortByNum() {
+	sort.Sort(&tFilesSortByNum{tFiles: tf})
+}
+
+// Returns sum of all tables size.
+func (tf tFiles) size() (sum int64) {
+	for _, t := range tf {
+		sum += t.size
+	}
+	return sum
+}
+
+// Searches smallest index of tables whose its smallest
+// key is after or equal with given key.
+func (tf tFiles) searchMin(icmp *iComparer, ikey internalKey) int {
+	return sort.Search(len(tf), func(i int) bool {
+		return icmp.Compare(tf[i].imin, ikey) >= 0
+	})
+}
+
+// Searches smallest index of tables whose its largest
+// key is after or equal with given key.
+func (tf tFiles) searchMax(icmp *iComparer, ikey internalKey) int {
+	return sort.Search(len(tf), func(i int) bool {
+		return icmp.Compare(tf[i].imax, ikey) >= 0
+	})
+}
+
+// Returns true if given key range overlaps with one or more
+// tables key range. If unsorted is true then binary search will not be used.
+func (tf tFiles) overlaps(icmp *iComparer, umin, umax []byte, unsorted bool) bool {
+	if unsorted {
+		// Check against all files.
+		for _, t := range tf {
+			if t.overlaps(icmp, umin, umax) {
+				return true
+			}
+		}
+		return false
+	}
+
+	i := 0
+	if len(umin) > 0 {
+		// Find the earliest possible internal key for min.
+		i = tf.searchMax(icmp, makeInternalKey(nil, umin, keyMaxSeq, keyTypeSeek))
+	}
+	if i >= len(tf) {
+		// Beginning of range is after all files, so no overlap.
+		return false
+	}
+	return !tf[i].before(icmp, umax)
+}
+
+// Returns tables whose its key range overlaps with given key range.
+// Range will be expanded if ukey found hop across tables.
+// If overlapped is true then the search will be restarted if umax
+// expanded.
+// The dst content will be overwritten.
+func (tf tFiles) getOverlaps(dst tFiles, icmp *iComparer, umin, umax []byte, overlapped bool) tFiles {
+	dst = dst[:0]
+	for i := 0; i < len(tf); {
+		t := tf[i]
+		if t.overlaps(icmp, umin, umax) {
+			if umin != nil && icmp.uCompare(t.imin.ukey(), umin) < 0 {
+				umin = t.imin.ukey()
+				dst = dst[:0]
+				i = 0
+				continue
+			} else if umax != nil && icmp.uCompare(t.imax.ukey(), umax) > 0 {
+				umax = t.imax.ukey()
+				// Restart search if it is overlapped.
+				if overlapped {
+					dst = dst[:0]
+					i = 0
+					continue
+				}
+			}
+
+			dst = append(dst, t)
+		}
+		i++
+	}
+
+	return dst
+}
+
+// Returns tables key range.
+func (tf tFiles) getRange(icmp *iComparer) (imin, imax internalKey) {
+	for i, t := range tf {
+		if i == 0 {
+			imin, imax = t.imin, t.imax
+			continue
+		}
+		if icmp.Compare(t.imin, imin) < 0 {
+			imin = t.imin
+		}
+		if icmp.Compare(t.imax, imax) > 0 {
+			imax = t.imax
+		}
+	}
+
+	return
+}
+
+// Creates iterator index from tables.
+func (tf tFiles) newIndexIterator(tops *tOps, icmp *iComparer, slice *util.Range, ro *opt.ReadOptions) iterator.IteratorIndexer {
+	if slice != nil {
+		var start, limit int
+		if slice.Start != nil {
+			start = tf.searchMax(icmp, internalKey(slice.Start))
+		}
+		if slice.Limit != nil {
+			limit = tf.searchMin(icmp, internalKey(slice.Limit))
+		} else {
+			limit = tf.Len()
+		}
+		tf = tf[start:limit]
+	}
+	return iterator.NewArrayIndexer(&tFilesArrayIndexer{
+		tFiles: tf,
+		tops:   tops,
+		icmp:   icmp,
+		slice:  slice,
+		ro:     ro,
+	})
+}
+
+// Tables iterator index.
+type tFilesArrayIndexer struct {
+	tFiles
+	tops  *tOps
+	icmp  *iComparer
+	slice *util.Range
+	ro    *opt.ReadOptions
+}
+
+func (a *tFilesArrayIndexer) Search(key []byte) int {
+	return a.searchMax(a.icmp, internalKey(key))
+}
+
+func (a *tFilesArrayIndexer) Get(i int) iterator.Iterator {
+	if i == 0 || i == a.Len()-1 {
+		return a.tops.newIterator(a.tFiles[i], a.slice, a.ro)
+	}
+	return a.tops.newIterator(a.tFiles[i], nil, a.ro)
+}
+
+// Helper type for sortByKey.
+type tFilesSortByKey struct {
+	tFiles
+	icmp *iComparer
+}
+
+func (x *tFilesSortByKey) Less(i, j int) bool {
+	return x.lessByKey(x.icmp, i, j)
+}
+
+// Helper type for sortByNum.
+type tFilesSortByNum struct {
+	tFiles
+}
+
+func (x *tFilesSortByNum) Less(i, j int) bool {
+	return x.lessByNum(i, j)
+}
+
+// Table operations.
+type tOps struct {
+	s            *session
+	noSync       bool
+	evictRemoved bool
+	cache        *cache.Cache
+	bcache       *cache.Cache
+	bpool        *util.BufferPool
+}
+
+// Creates an empty table and returns table writer.
+func (t *tOps) create() (*tWriter, error) {
+	fd := storage.FileDesc{Type: storage.TypeTable, Num: t.s.allocFileNum()}
+	fw, err := t.s.stor.Create(fd)
+	if err != nil {
+		return nil, err
+	}
+	return &tWriter{
+		t:  t,
+		fd: fd,
+		w:  fw,
+		tw: table.NewWriter(fw, t.s.o.Options),
+	}, nil
+}
+
+// Builds table from src iterator.
+func (t *tOps) createFrom(src iterator.Iterator) (f *tFile, n int, err error) {
+	w, err := t.create()
+	if err != nil {
+		return
+	}
+
+	defer func() {
+		if err != nil {
+			w.drop()
+		}
+	}()
+
+	for src.Next() {
+		err = w.append(src.Key(), src.Value())
+		if err != nil {
+			return
+		}
+	}
+	err = src.Error()
+	if err != nil {
+		return
+	}
+
+	n = w.tw.EntriesLen()
+	f, err = w.finish()
+	return
+}
+
+// Opens table. It returns a cache handle, which should
+// be released after use.
+func (t *tOps) open(f *tFile) (ch *cache.Handle, err error) {
+	ch = t.cache.Get(0, uint64(f.fd.Num), func() (size int, value cache.Value) {
+		var r storage.Reader
+		r, err = t.s.stor.Open(f.fd)
+		if err != nil {
+			return 0, nil
+		}
+
+		var bcache *cache.NamespaceGetter
+		if t.bcache != nil {
+			bcache = &cache.NamespaceGetter{Cache: t.bcache, NS: uint64(f.fd.Num)}
+		}
+
+		var tr *table.Reader
+		tr, err = table.NewReader(r, f.size, f.fd, bcache, t.bpool, t.s.o.Options)
+		if err != nil {
+			r.Close()
+			return 0, nil
+		}
+		return 1, tr
+
+	})
+	if ch == nil && err == nil {
+		err = ErrClosed
+	}
+	return
+}
+
+// Finds key/value pair whose key is greater than or equal to the
+// given key.
+func (t *tOps) find(f *tFile, key []byte, ro *opt.ReadOptions) (rkey, rvalue []byte, err error) {
+	ch, err := t.open(f)
+	if err != nil {
+		return nil, nil, err
+	}
+	defer ch.Release()
+	return ch.Value().(*table.Reader).Find(key, true, ro)
+}
+
+// Finds key that is greater than or equal to the given key.
+func (t *tOps) findKey(f *tFile, key []byte, ro *opt.ReadOptions) (rkey []byte, err error) {
+	ch, err := t.open(f)
+	if err != nil {
+		return nil, err
+	}
+	defer ch.Release()
+	return ch.Value().(*table.Reader).FindKey(key, true, ro)
+}
+
+// Returns approximate offset of the given key.
+func (t *tOps) offsetOf(f *tFile, key []byte) (offset int64, err error) {
+	ch, err := t.open(f)
+	if err != nil {
+		return
+	}
+	defer ch.Release()
+	return ch.Value().(*table.Reader).OffsetOf(key)
+}
+
+// Creates an iterator from the given table.
+func (t *tOps) newIterator(f *tFile, slice *util.Range, ro *opt.ReadOptions) iterator.Iterator {
+	ch, err := t.open(f)
+	if err != nil {
+		return iterator.NewEmptyIterator(err)
+	}
+	iter := ch.Value().(*table.Reader).NewIterator(slice, ro)
+	iter.SetReleaser(ch)
+	return iter
+}
+
+// Removes table from persistent storage. It waits until
+// no one use the the table.
+func (t *tOps) remove(f *tFile) {
+	t.cache.Delete(0, uint64(f.fd.Num), func() {
+		if err := t.s.stor.Remove(f.fd); err != nil {
+			t.s.logf("table@remove removing @%d %q", f.fd.Num, err)
+		} else {
+			t.s.logf("table@remove removed @%d", f.fd.Num)
+		}
+		if t.evictRemoved && t.bcache != nil {
+			t.bcache.EvictNS(uint64(f.fd.Num))
+		}
+	})
+}
+
+// Closes the table ops instance. It will close all tables,
+// regadless still used or not.
+func (t *tOps) close() {
+	t.bpool.Close()
+	t.cache.Close()
+	if t.bcache != nil {
+		t.bcache.CloseWeak()
+	}
+}
+
+// Creates new initialized table ops instance.
+func newTableOps(s *session) *tOps {
+	var (
+		cacher cache.Cacher
+		bcache *cache.Cache
+		bpool  *util.BufferPool
+	)
+	if s.o.GetOpenFilesCacheCapacity() > 0 {
+		cacher = cache.NewLRU(s.o.GetOpenFilesCacheCapacity())
+	}
+	if !s.o.GetDisableBlockCache() {
+		var bcacher cache.Cacher
+		if s.o.GetBlockCacheCapacity() > 0 {
+			bcacher = s.o.GetBlockCacher().New(s.o.GetBlockCacheCapacity())
+		}
+		bcache = cache.NewCache(bcacher)
+	}
+	if !s.o.GetDisableBufferPool() {
+		bpool = util.NewBufferPool(s.o.GetBlockSize() + 5)
+	}
+	return &tOps{
+		s:            s,
+		noSync:       s.o.GetNoSync(),
+		evictRemoved: s.o.GetBlockCacheEvictRemoved(),
+		cache:        cache.NewCache(cacher),
+		bcache:       bcache,
+		bpool:        bpool,
+	}
+}
+
+// tWriter wraps the table writer. It keep track of file descriptor
+// and added key range.
+type tWriter struct {
+	t *tOps
+
+	fd storage.FileDesc
+	w  storage.Writer
+	tw *table.Writer
+
+	first, last []byte
+}
+
+// Append key/value pair to the table.
+func (w *tWriter) append(key, value []byte) error {
+	if w.first == nil {
+		w.first = append([]byte{}, key...)
+	}
+	w.last = append(w.last[:0], key...)
+	return w.tw.Append(key, value)
+}
+
+// Returns true if the table is empty.
+func (w *tWriter) empty() bool {
+	return w.first == nil
+}
+
+// Closes the storage.Writer.
+func (w *tWriter) close() {
+	if w.w != nil {
+		w.w.Close()
+		w.w = nil
+	}
+}
+
+// Finalizes the table and returns table file.
+func (w *tWriter) finish() (f *tFile, err error) {
+	defer w.close()
+	err = w.tw.Close()
+	if err != nil {
+		return
+	}
+	if !w.t.noSync {
+		err = w.w.Sync()
+		if err != nil {
+			return
+		}
+	}
+	f = newTableFile(w.fd, int64(w.tw.BytesLen()), internalKey(w.first), internalKey(w.last))
+	return
+}
+
+// Drops the table.
+func (w *tWriter) drop() {
+	w.close()
+	w.t.s.stor.Remove(w.fd)
+	w.t.s.reuseFileNum(w.fd.Num)
+	w.tw = nil
+	w.first = nil
+	w.last = nil
+}

vendor/github.com/syndtr/goleveldb/leveldb/table/reader.go

@@ -0,0 +1,1139 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package table
+
+import (
+	"encoding/binary"
+	"fmt"
+	"io"
+	"sort"
+	"strings"
+	"sync"
+
+	"github.com/golang/snappy"
+
+	"github.com/syndtr/goleveldb/leveldb/cache"
+	"github.com/syndtr/goleveldb/leveldb/comparer"
+	"github.com/syndtr/goleveldb/leveldb/errors"
+	"github.com/syndtr/goleveldb/leveldb/filter"
+	"github.com/syndtr/goleveldb/leveldb/iterator"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+	"github.com/syndtr/goleveldb/leveldb/storage"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+// Reader errors.
+var (
+	ErrNotFound       = errors.ErrNotFound
+	ErrReaderReleased = errors.New("leveldb/table: reader released")
+	ErrIterReleased   = errors.New("leveldb/table: iterator released")
+)
+
+// ErrCorrupted describes error due to corruption. This error will be wrapped
+// with errors.ErrCorrupted.
+type ErrCorrupted struct {
+	Pos    int64
+	Size   int64
+	Kind   string
+	Reason string
+}
+
+func (e *ErrCorrupted) Error() string {
+	return fmt.Sprintf("leveldb/table: corruption on %s (pos=%d): %s", e.Kind, e.Pos, e.Reason)
+}
+
+func max(x, y int) int {
+	if x > y {
+		return x
+	}
+	return y
+}
+
+type block struct {
+	bpool          *util.BufferPool
+	bh             blockHandle
+	data           []byte
+	restartsLen    int
+	restartsOffset int
+}
+
+func (b *block) seek(cmp comparer.Comparer, rstart, rlimit int, key []byte) (index, offset int, err error) {
+	index = sort.Search(b.restartsLen-rstart-(b.restartsLen-rlimit), func(i int) bool {
+		offset := int(binary.LittleEndian.Uint32(b.data[b.restartsOffset+4*(rstart+i):]))
+		offset++                                    // shared always zero, since this is a restart point
+		v1, n1 := binary.Uvarint(b.data[offset:])   // key length
+		_, n2 := binary.Uvarint(b.data[offset+n1:]) // value length
+		m := offset + n1 + n2
+		return cmp.Compare(b.data[m:m+int(v1)], key) > 0
+	}) + rstart - 1
+	if index < rstart {
+		// The smallest key is greater-than key sought.
+		index = rstart
+	}
+	offset = int(binary.LittleEndian.Uint32(b.data[b.restartsOffset+4*index:]))
+	return
+}
+
+func (b *block) restartIndex(rstart, rlimit, offset int) int {
+	return sort.Search(b.restartsLen-rstart-(b.restartsLen-rlimit), func(i int) bool {
+		return int(binary.LittleEndian.Uint32(b.data[b.restartsOffset+4*(rstart+i):])) > offset
+	}) + rstart - 1
+}
+
+func (b *block) restartOffset(index int) int {
+	return int(binary.LittleEndian.Uint32(b.data[b.restartsOffset+4*index:]))
+}
+
+func (b *block) entry(offset int) (key, value []byte, nShared, n int, err error) {
+	if offset >= b.restartsOffset {
+		if offset != b.restartsOffset {
+			err = &ErrCorrupted{Reason: "entries offset not aligned"}
+		}
+		return
+	}
+	v0, n0 := binary.Uvarint(b.data[offset:])       // Shared prefix length
+	v1, n1 := binary.Uvarint(b.data[offset+n0:])    // Key length
+	v2, n2 := binary.Uvarint(b.data[offset+n0+n1:]) // Value length
+	m := n0 + n1 + n2
+	n = m + int(v1) + int(v2)
+	if n0 <= 0 || n1 <= 0 || n2 <= 0 || offset+n > b.restartsOffset {
+		err = &ErrCorrupted{Reason: "entries corrupted"}
+		return
+	}
+	key = b.data[offset+m : offset+m+int(v1)]
+	value = b.data[offset+m+int(v1) : offset+n]
+	nShared = int(v0)
+	return
+}
+
+func (b *block) Release() {
+	b.bpool.Put(b.data)
+	b.bpool = nil
+	b.data = nil
+}
+
+type dir int
+
+const (
+	dirReleased dir = iota - 1
+	dirSOI
+	dirEOI
+	dirBackward
+	dirForward
+)
+
+type blockIter struct {
+	tr            *Reader
+	block         *block
+	blockReleaser util.Releaser
+	releaser      util.Releaser
+	key, value    []byte
+	offset        int
+	// Previous offset, only filled by Next.
+	prevOffset   int
+	prevNode     []int
+	prevKeys     []byte
+	restartIndex int
+	// Iterator direction.
+	dir dir
+	// Restart index slice range.
+	riStart int
+	riLimit int
+	// Offset slice range.
+	offsetStart     int
+	offsetRealStart int
+	offsetLimit     int
+	// Error.
+	err error
+}
+
+func (i *blockIter) sErr(err error) {
+	i.err = err
+	i.key = nil
+	i.value = nil
+	i.prevNode = nil
+	i.prevKeys = nil
+}
+
+func (i *blockIter) reset() {
+	if i.dir == dirBackward {
+		i.prevNode = i.prevNode[:0]
+		i.prevKeys = i.prevKeys[:0]
+	}
+	i.restartIndex = i.riStart
+	i.offset = i.offsetStart
+	i.dir = dirSOI
+	i.key = i.key[:0]
+	i.value = nil
+}
+
+func (i *blockIter) isFirst() bool {
+	switch i.dir {
+	case dirForward:
+		return i.prevOffset == i.offsetRealStart
+	case dirBackward:
+		return len(i.prevNode) == 1 && i.restartIndex == i.riStart
+	}
+	return false
+}
+
+func (i *blockIter) isLast() bool {
+	switch i.dir {
+	case dirForward, dirBackward:
+		return i.offset == i.offsetLimit
+	}
+	return false
+}
+
+func (i *blockIter) First() bool {
+	if i.err != nil {
+		return false
+	} else if i.dir == dirReleased {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	if i.dir == dirBackward {
+		i.prevNode = i.prevNode[:0]
+		i.prevKeys = i.prevKeys[:0]
+	}
+	i.dir = dirSOI
+	return i.Next()
+}
+
+func (i *blockIter) Last() bool {
+	if i.err != nil {
+		return false
+	} else if i.dir == dirReleased {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	if i.dir == dirBackward {
+		i.prevNode = i.prevNode[:0]
+		i.prevKeys = i.prevKeys[:0]
+	}
+	i.dir = dirEOI
+	return i.Prev()
+}
+
+func (i *blockIter) Seek(key []byte) bool {
+	if i.err != nil {
+		return false
+	} else if i.dir == dirReleased {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	ri, offset, err := i.block.seek(i.tr.cmp, i.riStart, i.riLimit, key)
+	if err != nil {
+		i.sErr(err)
+		return false
+	}
+	i.restartIndex = ri
+	i.offset = max(i.offsetStart, offset)
+	if i.dir == dirSOI || i.dir == dirEOI {
+		i.dir = dirForward
+	}
+	for i.Next() {
+		if i.tr.cmp.Compare(i.key, key) >= 0 {
+			return true
+		}
+	}
+	return false
+}
+
+func (i *blockIter) Next() bool {
+	if i.dir == dirEOI || i.err != nil {
+		return false
+	} else if i.dir == dirReleased {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	if i.dir == dirSOI {
+		i.restartIndex = i.riStart
+		i.offset = i.offsetStart
+	} else if i.dir == dirBackward {
+		i.prevNode = i.prevNode[:0]
+		i.prevKeys = i.prevKeys[:0]
+	}
+	for i.offset < i.offsetRealStart {
+		key, value, nShared, n, err := i.block.entry(i.offset)
+		if err != nil {
+			i.sErr(i.tr.fixErrCorruptedBH(i.block.bh, err))
+			return false
+		}
+		if n == 0 {
+			i.dir = dirEOI
+			return false
+		}
+		i.key = append(i.key[:nShared], key...)
+		i.value = value
+		i.offset += n
+	}
+	if i.offset >= i.offsetLimit {
+		i.dir = dirEOI
+		if i.offset != i.offsetLimit {
+			i.sErr(i.tr.newErrCorruptedBH(i.block.bh, "entries offset not aligned"))
+		}
+		return false
+	}
+	key, value, nShared, n, err := i.block.entry(i.offset)
+	if err != nil {
+		i.sErr(i.tr.fixErrCorruptedBH(i.block.bh, err))
+		return false
+	}
+	if n == 0 {
+		i.dir = dirEOI
+		return false
+	}
+	i.key = append(i.key[:nShared], key...)
+	i.value = value
+	i.prevOffset = i.offset
+	i.offset += n
+	i.dir = dirForward
+	return true
+}
+
+func (i *blockIter) Prev() bool {
+	if i.dir == dirSOI || i.err != nil {
+		return false
+	} else if i.dir == dirReleased {
+		i.err = ErrIterReleased
+		return false
+	}
+
+	var ri int
+	if i.dir == dirForward {
+		// Change direction.
+		i.offset = i.prevOffset
+		if i.offset == i.offsetRealStart {
+			i.dir = dirSOI
+			return false
+		}
+		ri = i.block.restartIndex(i.restartIndex, i.riLimit, i.offset)
+		i.dir = dirBackward
+	} else if i.dir == dirEOI {
+		// At the end of iterator.
+		i.restartIndex = i.riLimit
+		i.offset = i.offsetLimit
+		if i.offset == i.offsetRealStart {
+			i.dir = dirSOI
+			return false
+		}
+		ri = i.riLimit - 1
+		i.dir = dirBackward
+	} else if len(i.prevNode) == 1 {
+		// This is the end of a restart range.
+		i.offset = i.prevNode[0]
+		i.prevNode = i.prevNode[:0]
+		if i.restartIndex == i.riStart {
+			i.dir = dirSOI
+			return false
+		}
+		i.restartIndex--
+		ri = i.restartIndex
+	} else {
+		// In the middle of restart range, get from cache.
+		n := len(i.prevNode) - 3
+		node := i.prevNode[n:]
+		i.prevNode = i.prevNode[:n]
+		// Get the key.
+		ko := node[0]
+		i.key = append(i.key[:0], i.prevKeys[ko:]...)
+		i.prevKeys = i.prevKeys[:ko]
+		// Get the value.
+		vo := node[1]
+		vl := vo + node[2]
+		i.value = i.block.data[vo:vl]
+		i.offset = vl
+		return true
+	}
+	// Build entries cache.
+	i.key = i.key[:0]
+	i.value = nil
+	offset := i.block.restartOffset(ri)
+	if offset == i.offset {
+		ri--
+		if ri < 0 {
+			i.dir = dirSOI
+			return false
+		}
+		offset = i.block.restartOffset(ri)
+	}
+	i.prevNode = append(i.prevNode, offset)
+	for {
+		key, value, nShared, n, err := i.block.entry(offset)
+		if err != nil {
+			i.sErr(i.tr.fixErrCorruptedBH(i.block.bh, err))
+			return false
+		}
+		if offset >= i.offsetRealStart {
+			if i.value != nil {
+				// Appends 3 variables:
+				// 1. Previous keys offset
+				// 2. Value offset in the data block
+				// 3. Value length
+				i.prevNode = append(i.prevNode, len(i.prevKeys), offset-len(i.value), len(i.value))
+				i.prevKeys = append(i.prevKeys, i.key...)
+			}
+			i.value = value
+		}
+		i.key = append(i.key[:nShared], key...)
+		offset += n
+		// Stop if target offset reached.
+		if offset >= i.offset {
+			if offset != i.offset {
+				i.sErr(i.tr.newErrCorruptedBH(i.block.bh, "entries offset not aligned"))
+				return false
+			}
+
+			break
+		}
+	}
+	i.restartIndex = ri
+	i.offset = offset
+	return true
+}
+
+func (i *blockIter) Key() []byte {
+	if i.err != nil || i.dir <= dirEOI {
+		return nil
+	}
+	return i.key
+}
+
+func (i *blockIter) Value() []byte {
+	if i.err != nil || i.dir <= dirEOI {
+		return nil
+	}
+	return i.value
+}
+
+func (i *blockIter) Release() {
+	if i.dir != dirReleased {
+		i.tr = nil
+		i.block = nil
+		i.prevNode = nil
+		i.prevKeys = nil
+		i.key = nil
+		i.value = nil
+		i.dir = dirReleased
+		if i.blockReleaser != nil {
+			i.blockReleaser.Release()
+			i.blockReleaser = nil
+		}
+		if i.releaser != nil {
+			i.releaser.Release()
+			i.releaser = nil
+		}
+	}
+}
+
+func (i *blockIter) SetReleaser(releaser util.Releaser) {
+	if i.dir == dirReleased {
+		panic(util.ErrReleased)
+	}
+	if i.releaser != nil && releaser != nil {
+		panic(util.ErrHasReleaser)
+	}
+	i.releaser = releaser
+}
+
+func (i *blockIter) Valid() bool {
+	return i.err == nil && (i.dir == dirBackward || i.dir == dirForward)
+}
+
+func (i *blockIter) Error() error {
+	return i.err
+}
+
+type filterBlock struct {
+	bpool      *util.BufferPool
+	data       []byte
+	oOffset    int
+	baseLg     uint
+	filtersNum int
+}
+
+func (b *filterBlock) contains(filter filter.Filter, offset uint64, key []byte) bool {
+	i := int(offset >> b.baseLg)
+	if i < b.filtersNum {
+		o := b.data[b.oOffset+i*4:]
+		n := int(binary.LittleEndian.Uint32(o))
+		m := int(binary.LittleEndian.Uint32(o[4:]))
+		if n < m && m <= b.oOffset {
+			return filter.Contains(b.data[n:m], key)
+		} else if n == m {
+			return false
+		}
+	}
+	return true
+}
+
+func (b *filterBlock) Release() {
+	b.bpool.Put(b.data)
+	b.bpool = nil
+	b.data = nil
+}
+
+type indexIter struct {
+	*blockIter
+	tr    *Reader
+	slice *util.Range
+	// Options
+	fillCache bool
+}
+
+func (i *indexIter) Get() iterator.Iterator {
+	value := i.Value()
+	if value == nil {
+		return nil
+	}
+	dataBH, n := decodeBlockHandle(value)
+	if n == 0 {
+		return iterator.NewEmptyIterator(i.tr.newErrCorruptedBH(i.tr.indexBH, "bad data block handle"))
+	}
+
+	var slice *util.Range
+	if i.slice != nil && (i.blockIter.isFirst() || i.blockIter.isLast()) {
+		slice = i.slice
+	}
+	return i.tr.getDataIterErr(dataBH, slice, i.tr.verifyChecksum, i.fillCache)
+}
+
+// Reader is a table reader.
+type Reader struct {
+	mu     sync.RWMutex
+	fd     storage.FileDesc
+	reader io.ReaderAt
+	cache  *cache.NamespaceGetter
+	err    error
+	bpool  *util.BufferPool
+	// Options
+	o              *opt.Options
+	cmp            comparer.Comparer
+	filter         filter.Filter
+	verifyChecksum bool
+
+	dataEnd                   int64
+	metaBH, indexBH, filterBH blockHandle
+	indexBlock                *block
+	filterBlock               *filterBlock
+}
+
+func (r *Reader) blockKind(bh blockHandle) string {
+	switch bh.offset {
+	case r.metaBH.offset:
+		return "meta-block"
+	case r.indexBH.offset:
+		return "index-block"
+	case r.filterBH.offset:
+		if r.filterBH.length > 0 {
+			return "filter-block"
+		}
+	}
+	return "data-block"
+}
+
+func (r *Reader) newErrCorrupted(pos, size int64, kind, reason string) error {
+	return &errors.ErrCorrupted{Fd: r.fd, Err: &ErrCorrupted{Pos: pos, Size: size, Kind: kind, Reason: reason}}
+}
+
+func (r *Reader) newErrCorruptedBH(bh blockHandle, reason string) error {
+	return r.newErrCorrupted(int64(bh.offset), int64(bh.length), r.blockKind(bh), reason)
+}
+
+func (r *Reader) fixErrCorruptedBH(bh blockHandle, err error) error {
+	if cerr, ok := err.(*ErrCorrupted); ok {
+		cerr.Pos = int64(bh.offset)
+		cerr.Size = int64(bh.length)
+		cerr.Kind = r.blockKind(bh)
+		return &errors.ErrCorrupted{Fd: r.fd, Err: cerr}
+	}
+	return err
+}
+
+func (r *Reader) readRawBlock(bh blockHandle, verifyChecksum bool) ([]byte, error) {
+	data := r.bpool.Get(int(bh.length + blockTrailerLen))
+	if _, err := r.reader.ReadAt(data, int64(bh.offset)); err != nil && err != io.EOF {
+		return nil, err
+	}
+
+	if verifyChecksum {
+		n := bh.length + 1
+		checksum0 := binary.LittleEndian.Uint32(data[n:])
+		checksum1 := util.NewCRC(data[:n]).Value()
+		if checksum0 != checksum1 {
+			r.bpool.Put(data)
+			return nil, r.newErrCorruptedBH(bh, fmt.Sprintf("checksum mismatch, want=%#x got=%#x", checksum0, checksum1))
+		}
+	}
+
+	switch data[bh.length] {
+	case blockTypeNoCompression:
+		data = data[:bh.length]
+	case blockTypeSnappyCompression:
+		decLen, err := snappy.DecodedLen(data[:bh.length])
+		if err != nil {
+			r.bpool.Put(data)
+			return nil, r.newErrCorruptedBH(bh, err.Error())
+		}
+		decData := r.bpool.Get(decLen)
+		decData, err = snappy.Decode(decData, data[:bh.length])
+		r.bpool.Put(data)
+		if err != nil {
+			r.bpool.Put(decData)
+			return nil, r.newErrCorruptedBH(bh, err.Error())
+		}
+		data = decData
+	default:
+		r.bpool.Put(data)
+		return nil, r.newErrCorruptedBH(bh, fmt.Sprintf("unknown compression type %#x", data[bh.length]))
+	}
+	return data, nil
+}
+
+func (r *Reader) readBlock(bh blockHandle, verifyChecksum bool) (*block, error) {
+	data, err := r.readRawBlock(bh, verifyChecksum)
+	if err != nil {
+		return nil, err
+	}
+	restartsLen := int(binary.LittleEndian.Uint32(data[len(data)-4:]))
+	b := &block{
+		bpool:          r.bpool,
+		bh:             bh,
+		data:           data,
+		restartsLen:    restartsLen,
+		restartsOffset: len(data) - (restartsLen+1)*4,
+	}
+	return b, nil
+}
+
+func (r *Reader) readBlockCached(bh blockHandle, verifyChecksum, fillCache bool) (*block, util.Releaser, error) {
+	if r.cache != nil {
+		var (
+			err error
+			ch  *cache.Handle
+		)
+		if fillCache {
+			ch = r.cache.Get(bh.offset, func() (size int, value cache.Value) {
+				var b *block
+				b, err = r.readBlock(bh, verifyChecksum)
+				if err != nil {
+					return 0, nil
+				}
+				return cap(b.data), b
+			})
+		} else {
+			ch = r.cache.Get(bh.offset, nil)
+		}
+		if ch != nil {
+			b, ok := ch.Value().(*block)
+			if !ok {
+				ch.Release()
+				return nil, nil, errors.New("leveldb/table: inconsistent block type")
+			}
+			return b, ch, err
+		} else if err != nil {
+			return nil, nil, err
+		}
+	}
+
+	b, err := r.readBlock(bh, verifyChecksum)
+	return b, b, err
+}
+
+func (r *Reader) readFilterBlock(bh blockHandle) (*filterBlock, error) {
+	data, err := r.readRawBlock(bh, true)
+	if err != nil {
+		return nil, err
+	}
+	n := len(data)
+	if n < 5 {
+		return nil, r.newErrCorruptedBH(bh, "too short")
+	}
+	m := n - 5
+	oOffset := int(binary.LittleEndian.Uint32(data[m:]))
+	if oOffset > m {
+		return nil, r.newErrCorruptedBH(bh, "invalid data-offsets offset")
+	}
+	b := &filterBlock{
+		bpool:      r.bpool,
+		data:       data,
+		oOffset:    oOffset,
+		baseLg:     uint(data[n-1]),
+		filtersNum: (m - oOffset) / 4,
+	}
+	return b, nil
+}
+
+func (r *Reader) readFilterBlockCached(bh blockHandle, fillCache bool) (*filterBlock, util.Releaser, error) {
+	if r.cache != nil {
+		var (
+			err error
+			ch  *cache.Handle
+		)
+		if fillCache {
+			ch = r.cache.Get(bh.offset, func() (size int, value cache.Value) {
+				var b *filterBlock
+				b, err = r.readFilterBlock(bh)
+				if err != nil {
+					return 0, nil
+				}
+				return cap(b.data), b
+			})
+		} else {
+			ch = r.cache.Get(bh.offset, nil)
+		}
+		if ch != nil {
+			b, ok := ch.Value().(*filterBlock)
+			if !ok {
+				ch.Release()
+				return nil, nil, errors.New("leveldb/table: inconsistent block type")
+			}
+			return b, ch, err
+		} else if err != nil {
+			return nil, nil, err
+		}
+	}
+
+	b, err := r.readFilterBlock(bh)
+	return b, b, err
+}
+
+func (r *Reader) getIndexBlock(fillCache bool) (b *block, rel util.Releaser, err error) {
+	if r.indexBlock == nil {
+		return r.readBlockCached(r.indexBH, true, fillCache)
+	}
+	return r.indexBlock, util.NoopReleaser{}, nil
+}
+
+func (r *Reader) getFilterBlock(fillCache bool) (*filterBlock, util.Releaser, error) {
+	if r.filterBlock == nil {
+		return r.readFilterBlockCached(r.filterBH, fillCache)
+	}
+	return r.filterBlock, util.NoopReleaser{}, nil
+}
+
+func (r *Reader) newBlockIter(b *block, bReleaser util.Releaser, slice *util.Range, inclLimit bool) *blockIter {
+	bi := &blockIter{
+		tr:            r,
+		block:         b,
+		blockReleaser: bReleaser,
+		// Valid key should never be nil.
+		key:             make([]byte, 0),
+		dir:             dirSOI,
+		riStart:         0,
+		riLimit:         b.restartsLen,
+		offsetStart:     0,
+		offsetRealStart: 0,
+		offsetLimit:     b.restartsOffset,
+	}
+	if slice != nil {
+		if slice.Start != nil {
+			if bi.Seek(slice.Start) {
+				bi.riStart = b.restartIndex(bi.restartIndex, b.restartsLen, bi.prevOffset)
+				bi.offsetStart = b.restartOffset(bi.riStart)
+				bi.offsetRealStart = bi.prevOffset
+			} else {
+				bi.riStart = b.restartsLen
+				bi.offsetStart = b.restartsOffset
+				bi.offsetRealStart = b.restartsOffset
+			}
+		}
+		if slice.Limit != nil {
+			if bi.Seek(slice.Limit) && (!inclLimit || bi.Next()) {
+				bi.offsetLimit = bi.prevOffset
+				bi.riLimit = bi.restartIndex + 1
+			}
+		}
+		bi.reset()
+		if bi.offsetStart > bi.offsetLimit {
+			bi.sErr(errors.New("leveldb/table: invalid slice range"))
+		}
+	}
+	return bi
+}
+
+func (r *Reader) getDataIter(dataBH blockHandle, slice *util.Range, verifyChecksum, fillCache bool) iterator.Iterator {
+	b, rel, err := r.readBlockCached(dataBH, verifyChecksum, fillCache)
+	if err != nil {
+		return iterator.NewEmptyIterator(err)
+	}
+	return r.newBlockIter(b, rel, slice, false)
+}
+
+func (r *Reader) getDataIterErr(dataBH blockHandle, slice *util.Range, verifyChecksum, fillCache bool) iterator.Iterator {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+
+	if r.err != nil {
+		return iterator.NewEmptyIterator(r.err)
+	}
+
+	return r.getDataIter(dataBH, slice, verifyChecksum, fillCache)
+}
+
+// NewIterator creates an iterator from the table.
+//
+// Slice allows slicing the iterator to only contains keys in the given
+// range. A nil Range.Start is treated as a key before all keys in the
+// table. And a nil Range.Limit is treated as a key after all keys in
+// the table.
+//
+// WARNING: Any slice returned by interator (e.g. slice returned by calling
+// Iterator.Key() or Iterator.Key() methods), its content should not be modified
+// unless noted otherwise.
+//
+// The returned iterator is not safe for concurrent use and should be released
+// after use.
+//
+// Also read Iterator documentation of the leveldb/iterator package.
+func (r *Reader) NewIterator(slice *util.Range, ro *opt.ReadOptions) iterator.Iterator {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+
+	if r.err != nil {
+		return iterator.NewEmptyIterator(r.err)
+	}
+
+	fillCache := !ro.GetDontFillCache()
+	indexBlock, rel, err := r.getIndexBlock(fillCache)
+	if err != nil {
+		return iterator.NewEmptyIterator(err)
+	}
+	index := &indexIter{
+		blockIter: r.newBlockIter(indexBlock, rel, slice, true),
+		tr:        r,
+		slice:     slice,
+		fillCache: !ro.GetDontFillCache(),
+	}
+	return iterator.NewIndexedIterator(index, opt.GetStrict(r.o, ro, opt.StrictReader))
+}
+
+func (r *Reader) find(key []byte, filtered bool, ro *opt.ReadOptions, noValue bool) (rkey, value []byte, err error) {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+
+	if r.err != nil {
+		err = r.err
+		return
+	}
+
+	indexBlock, rel, err := r.getIndexBlock(true)
+	if err != nil {
+		return
+	}
+	defer rel.Release()
+
+	index := r.newBlockIter(indexBlock, nil, nil, true)
+	defer index.Release()
+
+	if !index.Seek(key) {
+		if err = index.Error(); err == nil {
+			err = ErrNotFound
+		}
+		return
+	}
+
+	dataBH, n := decodeBlockHandle(index.Value())
+	if n == 0 {
+		r.err = r.newErrCorruptedBH(r.indexBH, "bad data block handle")
+		return nil, nil, r.err
+	}
+
+	// The filter should only used for exact match.
+	if filtered && r.filter != nil {
+		filterBlock, frel, ferr := r.getFilterBlock(true)
+		if ferr == nil {
+			if !filterBlock.contains(r.filter, dataBH.offset, key) {
+				frel.Release()
+				return nil, nil, ErrNotFound
+			}
+			frel.Release()
+		} else if !errors.IsCorrupted(ferr) {
+			return nil, nil, ferr
+		}
+	}
+
+	data := r.getDataIter(dataBH, nil, r.verifyChecksum, !ro.GetDontFillCache())
+	if !data.Seek(key) {
+		data.Release()
+		if err = data.Error(); err != nil {
+			return
+		}
+
+		// The nearest greater-than key is the first key of the next block.
+		if !index.Next() {
+			if err = index.Error(); err == nil {
+				err = ErrNotFound
+			}
+			return
+		}
+
+		dataBH, n = decodeBlockHandle(index.Value())
+		if n == 0 {
+			r.err = r.newErrCorruptedBH(r.indexBH, "bad data block handle")
+			return nil, nil, r.err
+		}
+
+		data = r.getDataIter(dataBH, nil, r.verifyChecksum, !ro.GetDontFillCache())
+		if !data.Next() {
+			data.Release()
+			if err = data.Error(); err == nil {
+				err = ErrNotFound
+			}
+			return
+		}
+	}
+
+	// Key doesn't use block buffer, no need to copy the buffer.
+	rkey = data.Key()
+	if !noValue {
+		if r.bpool == nil {
+			value = data.Value()
+		} else {
+			// Value does use block buffer, and since the buffer will be
+			// recycled, it need to be copied.
+			value = append([]byte{}, data.Value()...)
+		}
+	}
+	data.Release()
+	return
+}
+
+// Find finds key/value pair whose key is greater than or equal to the
+// given key. It returns ErrNotFound if the table doesn't contain
+// such pair.
+// If filtered is true then the nearest 'block' will be checked against
+// 'filter data' (if present) and will immediately return ErrNotFound if
+// 'filter data' indicates that such pair doesn't exist.
+//
+// The caller may modify the contents of the returned slice as it is its
+// own copy.
+// It is safe to modify the contents of the argument after Find returns.
+func (r *Reader) Find(key []byte, filtered bool, ro *opt.ReadOptions) (rkey, value []byte, err error) {
+	return r.find(key, filtered, ro, false)
+}
+
+// FindKey finds key that is greater than or equal to the given key.
+// It returns ErrNotFound if the table doesn't contain such key.
+// If filtered is true then the nearest 'block' will be checked against
+// 'filter data' (if present) and will immediately return ErrNotFound if
+// 'filter data' indicates that such key doesn't exist.
+//
+// The caller may modify the contents of the returned slice as it is its
+// own copy.
+// It is safe to modify the contents of the argument after Find returns.
+func (r *Reader) FindKey(key []byte, filtered bool, ro *opt.ReadOptions) (rkey []byte, err error) {
+	rkey, _, err = r.find(key, filtered, ro, true)
+	return
+}
+
+// Get gets the value for the given key. It returns errors.ErrNotFound
+// if the table does not contain the key.
+//
+// The caller may modify the contents of the returned slice as it is its
+// own copy.
+// It is safe to modify the contents of the argument after Find returns.
+func (r *Reader) Get(key []byte, ro *opt.ReadOptions) (value []byte, err error) {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+
+	if r.err != nil {
+		err = r.err
+		return
+	}
+
+	rkey, value, err := r.find(key, false, ro, false)
+	if err == nil && r.cmp.Compare(rkey, key) != 0 {
+		value = nil
+		err = ErrNotFound
+	}
+	return
+}
+
+// OffsetOf returns approximate offset for the given key.
+//
+// It is safe to modify the contents of the argument after Get returns.
+func (r *Reader) OffsetOf(key []byte) (offset int64, err error) {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+
+	if r.err != nil {
+		err = r.err
+		return
+	}
+
+	indexBlock, rel, err := r.readBlockCached(r.indexBH, true, true)
+	if err != nil {
+		return
+	}
+	defer rel.Release()
+
+	index := r.newBlockIter(indexBlock, nil, nil, true)
+	defer index.Release()
+	if index.Seek(key) {
+		dataBH, n := decodeBlockHandle(index.Value())
+		if n == 0 {
+			r.err = r.newErrCorruptedBH(r.indexBH, "bad data block handle")
+			return
+		}
+		offset = int64(dataBH.offset)
+		return
+	}
+	err = index.Error()
+	if err == nil {
+		offset = r.dataEnd
+	}
+	return
+}
+
+// Release implements util.Releaser.
+// It also close the file if it is an io.Closer.
+func (r *Reader) Release() {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	if closer, ok := r.reader.(io.Closer); ok {
+		closer.Close()
+	}
+	if r.indexBlock != nil {
+		r.indexBlock.Release()
+		r.indexBlock = nil
+	}
+	if r.filterBlock != nil {
+		r.filterBlock.Release()
+		r.filterBlock = nil
+	}
+	r.reader = nil
+	r.cache = nil
+	r.bpool = nil
+	r.err = ErrReaderReleased
+}
+
+// NewReader creates a new initialized table reader for the file.
+// The fi, cache and bpool is optional and can be nil.
+//
+// The returned table reader instance is safe for concurrent use.
+func NewReader(f io.ReaderAt, size int64, fd storage.FileDesc, cache *cache.NamespaceGetter, bpool *util.BufferPool, o *opt.Options) (*Reader, error) {
+	if f == nil {
+		return nil, errors.New("leveldb/table: nil file")
+	}
+
+	r := &Reader{
+		fd:             fd,
+		reader:         f,
+		cache:          cache,
+		bpool:          bpool,
+		o:              o,
+		cmp:            o.GetComparer(),
+		verifyChecksum: o.GetStrict(opt.StrictBlockChecksum),
+	}
+
+	if size < footerLen {
+		r.err = r.newErrCorrupted(0, size, "table", "too small")
+		return r, nil
+	}
+
+	footerPos := size - footerLen
+	var footer [footerLen]byte
+	if _, err := r.reader.ReadAt(footer[:], footerPos); err != nil && err != io.EOF {
+		return nil, err
+	}
+	if string(footer[footerLen-len(magic):footerLen]) != magic {
+		r.err = r.newErrCorrupted(footerPos, footerLen, "table-footer", "bad magic number")
+		return r, nil
+	}
+
+	var n int
+	// Decode the metaindex block handle.
+	r.metaBH, n = decodeBlockHandle(footer[:])
+	if n == 0 {
+		r.err = r.newErrCorrupted(footerPos, footerLen, "table-footer", "bad metaindex block handle")
+		return r, nil
+	}
+
+	// Decode the index block handle.
+	r.indexBH, n = decodeBlockHandle(footer[n:])
+	if n == 0 {
+		r.err = r.newErrCorrupted(footerPos, footerLen, "table-footer", "bad index block handle")
+		return r, nil
+	}
+
+	// Read metaindex block.
+	metaBlock, err := r.readBlock(r.metaBH, true)
+	if err != nil {
+		if errors.IsCorrupted(err) {
+			r.err = err
+			return r, nil
+		}
+		return nil, err
+	}
+
+	// Set data end.
+	r.dataEnd = int64(r.metaBH.offset)
+
+	// Read metaindex.
+	metaIter := r.newBlockIter(metaBlock, nil, nil, true)
+	for metaIter.Next() {
+		key := string(metaIter.Key())
+		if !strings.HasPrefix(key, "filter.") {
+			continue
+		}
+		fn := key[7:]
+		if f0 := o.GetFilter(); f0 != nil && f0.Name() == fn {
+			r.filter = f0
+		} else {
+			for _, f0 := range o.GetAltFilters() {
+				if f0.Name() == fn {
+					r.filter = f0
+					break
+				}
+			}
+		}
+		if r.filter != nil {
+			filterBH, n := decodeBlockHandle(metaIter.Value())
+			if n == 0 {
+				continue
+			}
+			r.filterBH = filterBH
+			// Update data end.
+			r.dataEnd = int64(filterBH.offset)
+			break
+		}
+	}
+	metaIter.Release()
+	metaBlock.Release()
+
+	// Cache index and filter block locally, since we don't have global cache.
+	if cache == nil {
+		r.indexBlock, err = r.readBlock(r.indexBH, true)
+		if err != nil {
+			if errors.IsCorrupted(err) {
+				r.err = err
+				return r, nil
+			}
+			return nil, err
+		}
+		if r.filter != nil {
+			r.filterBlock, err = r.readFilterBlock(r.filterBH)
+			if err != nil {
+				if !errors.IsCorrupted(err) {
+					return nil, err
+				}
+
+				// Don't use filter then.
+				r.filter = nil
+			}
+		}
+	}
+
+	return r, nil
+}

vendor/github.com/syndtr/goleveldb/leveldb/table/table.go

@@ -0,0 +1,177 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Package table allows read and write sorted key/value.
+package table
+
+import (
+	"encoding/binary"
+)
+
+/*
+Table:
+
+Table is consist of one or more data blocks, an optional filter block
+a metaindex block, an index block and a table footer. Metaindex block
+is a special block used to keep parameters of the table, such as filter
+block name and its block handle. Index block is a special block used to
+keep record of data blocks offset and length, index block use one as
+restart interval. The key used by index block are the last key of preceding
+block, shorter separator of adjacent blocks or shorter successor of the
+last key of the last block. Filter block is an optional block contains
+sequence of filter data generated by a filter generator.
+
+Table data structure:
+                                                         + optional
+                                                        /
+    +--------------+--------------+--------------+------+-------+-----------------+-------------+--------+
+    | data block 1 |      ...     | data block n | filter block | metaindex block | index block | footer |
+    +--------------+--------------+--------------+--------------+-----------------+-------------+--------+
+
+    Each block followed by a 5-bytes trailer contains compression type and checksum.
+
+Table block trailer:
+
+    +---------------------------+-------------------+
+    | compression type (1-byte) | checksum (4-byte) |
+    +---------------------------+-------------------+
+
+    The checksum is a CRC-32 computed using Castagnoli's polynomial. Compression
+    type also included in the checksum.
+
+Table footer:
+
+      +------------------- 40-bytes -------------------+
+     /                                                  \
+    +------------------------+--------------------+------+-----------------+
+    | metaindex block handle / index block handle / ---- | magic (8-bytes) |
+    +------------------------+--------------------+------+-----------------+
+
+    The magic are first 64-bit of SHA-1 sum of "http://code.google.com/p/leveldb/".
+
+NOTE: All fixed-length integer are little-endian.
+*/
+
+/*
+Block:
+
+Block is consist of one or more key/value entries and a block trailer.
+Block entry shares key prefix with its preceding key until a restart
+point reached. A block should contains at least one restart point.
+First restart point are always zero.
+
+Block data structure:
+
+      + restart point                 + restart point (depends on restart interval)
+     /                               /
+    +---------------+---------------+---------------+---------------+---------+
+    | block entry 1 | block entry 2 |      ...      | block entry n | trailer |
+    +---------------+---------------+---------------+---------------+---------+
+
+Key/value entry:
+
+              +---- key len ----+
+             /                   \
+    +-------+---------+-----------+---------+--------------------+--------------+----------------+
+    | shared (varint) | not shared (varint) | value len (varint) | key (varlen) | value (varlen) |
+    +-----------------+---------------------+--------------------+--------------+----------------+
+
+    Block entry shares key prefix with its preceding key:
+    Conditions:
+        restart_interval=2
+        entry one  : key=deck,value=v1
+        entry two  : key=dock,value=v2
+        entry three: key=duck,value=v3
+    The entries will be encoded as follow:
+
+      + restart point (offset=0)                                                 + restart point (offset=16)
+     /                                                                          /
+    +-----+-----+-----+----------+--------+-----+-----+-----+---------+--------+-----+-----+-----+----------+--------+
+    |  0  |  4  |  2  |  "deck"  |  "v1"  |  1  |  3  |  2  |  "ock"  |  "v2"  |  0  |  4  |  2  |  "duck"  |  "v3"  |
+    +-----+-----+-----+----------+--------+-----+-----+-----+---------+--------+-----+-----+-----+----------+--------+
+     \                                   / \                                  / \                                   /
+      +----------- entry one -----------+   +----------- entry two ----------+   +---------- entry three ----------+
+
+    The block trailer will contains two restart points:
+
+    +------------+-----------+--------+
+    |     0      |    16     |   2    |
+    +------------+-----------+---+----+
+     \                      /     \
+      +-- restart points --+       + restart points length
+
+Block trailer:
+
+      +-- 4-bytes --+
+     /               \
+    +-----------------+-----------------+-----------------+------------------------------+
+    | restart point 1 |       ....      | restart point n | restart points len (4-bytes) |
+    +-----------------+-----------------+-----------------+------------------------------+
+
+
+NOTE: All fixed-length integer are little-endian.
+*/
+
+/*
+Filter block:
+
+Filter block consist of one or more filter data and a filter block trailer.
+The trailer contains filter data offsets, a trailer offset and a 1-byte base Lg.
+
+Filter block data structure:
+
+      + offset 1      + offset 2      + offset n      + trailer offset
+     /               /               /               /
+    +---------------+---------------+---------------+---------+
+    | filter data 1 |      ...      | filter data n | trailer |
+    +---------------+---------------+---------------+---------+
+
+Filter block trailer:
+
+      +- 4-bytes -+
+     /             \
+    +---------------+---------------+---------------+-------------------------------+------------------+
+    | data 1 offset |      ....     | data n offset | data-offsets offset (4-bytes) | base Lg (1-byte) |
+    +-------------- +---------------+---------------+-------------------------------+------------------+
+
+
+NOTE: All fixed-length integer are little-endian.
+*/
+
+const (
+	blockTrailerLen = 5
+	footerLen       = 48
+
+	magic = "\x57\xfb\x80\x8b\x24\x75\x47\xdb"
+
+	// The block type gives the per-block compression format.
+	// These constants are part of the file format and should not be changed.
+	blockTypeNoCompression     = 0
+	blockTypeSnappyCompression = 1
+
+	// Generate new filter every 2KB of data
+	filterBaseLg = 11
+	filterBase   = 1 << filterBaseLg
+)
+
+type blockHandle struct {
+	offset, length uint64
+}
+
+func decodeBlockHandle(src []byte) (blockHandle, int) {
+	offset, n := binary.Uvarint(src)
+	length, m := binary.Uvarint(src[n:])
+	if n == 0 || m == 0 {
+		return blockHandle{}, 0
+	}
+	return blockHandle{offset, length}, n + m
+}
+
+func encodeBlockHandle(dst []byte, b blockHandle) int {
+	n := binary.PutUvarint(dst, b.offset)
+	m := binary.PutUvarint(dst[n:], b.length)
+	return n + m
+}

vendor/github.com/syndtr/goleveldb/leveldb/table/writer.go

@@ -0,0 +1,375 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package table
+
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"io"
+
+	"github.com/golang/snappy"
+
+	"github.com/syndtr/goleveldb/leveldb/comparer"
+	"github.com/syndtr/goleveldb/leveldb/filter"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+func sharedPrefixLen(a, b []byte) int {
+	i, n := 0, len(a)
+	if n > len(b) {
+		n = len(b)
+	}
+	for i < n && a[i] == b[i] {
+		i++
+	}
+	return i
+}
+
+type blockWriter struct {
+	restartInterval int
+	buf             util.Buffer
+	nEntries        int
+	prevKey         []byte
+	restarts        []uint32
+	scratch         []byte
+}
+
+func (w *blockWriter) append(key, value []byte) {
+	nShared := 0
+	if w.nEntries%w.restartInterval == 0 {
+		w.restarts = append(w.restarts, uint32(w.buf.Len()))
+	} else {
+		nShared = sharedPrefixLen(w.prevKey, key)
+	}
+	n := binary.PutUvarint(w.scratch[0:], uint64(nShared))
+	n += binary.PutUvarint(w.scratch[n:], uint64(len(key)-nShared))
+	n += binary.PutUvarint(w.scratch[n:], uint64(len(value)))
+	w.buf.Write(w.scratch[:n])
+	w.buf.Write(key[nShared:])
+	w.buf.Write(value)
+	w.prevKey = append(w.prevKey[:0], key...)
+	w.nEntries++
+}
+
+func (w *blockWriter) finish() {
+	// Write restarts entry.
+	if w.nEntries == 0 {
+		// Must have at least one restart entry.
+		w.restarts = append(w.restarts, 0)
+	}
+	w.restarts = append(w.restarts, uint32(len(w.restarts)))
+	for _, x := range w.restarts {
+		buf4 := w.buf.Alloc(4)
+		binary.LittleEndian.PutUint32(buf4, x)
+	}
+}
+
+func (w *blockWriter) reset() {
+	w.buf.Reset()
+	w.nEntries = 0
+	w.restarts = w.restarts[:0]
+}
+
+func (w *blockWriter) bytesLen() int {
+	restartsLen := len(w.restarts)
+	if restartsLen == 0 {
+		restartsLen = 1
+	}
+	return w.buf.Len() + 4*restartsLen + 4
+}
+
+type filterWriter struct {
+	generator filter.FilterGenerator
+	buf       util.Buffer
+	nKeys     int
+	offsets   []uint32
+}
+
+func (w *filterWriter) add(key []byte) {
+	if w.generator == nil {
+		return
+	}
+	w.generator.Add(key)
+	w.nKeys++
+}
+
+func (w *filterWriter) flush(offset uint64) {
+	if w.generator == nil {
+		return
+	}
+	for x := int(offset / filterBase); x > len(w.offsets); {
+		w.generate()
+	}
+}
+
+func (w *filterWriter) finish() {
+	if w.generator == nil {
+		return
+	}
+	// Generate last keys.
+
+	if w.nKeys > 0 {
+		w.generate()
+	}
+	w.offsets = append(w.offsets, uint32(w.buf.Len()))
+	for _, x := range w.offsets {
+		buf4 := w.buf.Alloc(4)
+		binary.LittleEndian.PutUint32(buf4, x)
+	}
+	w.buf.WriteByte(filterBaseLg)
+}
+
+func (w *filterWriter) generate() {
+	// Record offset.
+	w.offsets = append(w.offsets, uint32(w.buf.Len()))
+	// Generate filters.
+	if w.nKeys > 0 {
+		w.generator.Generate(&w.buf)
+		w.nKeys = 0
+	}
+}
+
+// Writer is a table writer.
+type Writer struct {
+	writer io.Writer
+	err    error
+	// Options
+	cmp         comparer.Comparer
+	filter      filter.Filter
+	compression opt.Compression
+	blockSize   int
+
+	dataBlock   blockWriter
+	indexBlock  blockWriter
+	filterBlock filterWriter
+	pendingBH   blockHandle
+	offset      uint64
+	nEntries    int
+	// Scratch allocated enough for 5 uvarint. Block writer should not use
+	// first 20-bytes since it will be used to encode block handle, which
+	// then passed to the block writer itself.
+	scratch            [50]byte
+	comparerScratch    []byte
+	compressionScratch []byte
+}
+
+func (w *Writer) writeBlock(buf *util.Buffer, compression opt.Compression) (bh blockHandle, err error) {
+	// Compress the buffer if necessary.
+	var b []byte
+	if compression == opt.SnappyCompression {
+		// Allocate scratch enough for compression and block trailer.
+		if n := snappy.MaxEncodedLen(buf.Len()) + blockTrailerLen; len(w.compressionScratch) < n {
+			w.compressionScratch = make([]byte, n)
+		}
+		compressed := snappy.Encode(w.compressionScratch, buf.Bytes())
+		n := len(compressed)
+		b = compressed[:n+blockTrailerLen]
+		b[n] = blockTypeSnappyCompression
+	} else {
+		tmp := buf.Alloc(blockTrailerLen)
+		tmp[0] = blockTypeNoCompression
+		b = buf.Bytes()
+	}
+
+	// Calculate the checksum.
+	n := len(b) - 4
+	checksum := util.NewCRC(b[:n]).Value()
+	binary.LittleEndian.PutUint32(b[n:], checksum)
+
+	// Write the buffer to the file.
+	_, err = w.writer.Write(b)
+	if err != nil {
+		return
+	}
+	bh = blockHandle{w.offset, uint64(len(b) - blockTrailerLen)}
+	w.offset += uint64(len(b))
+	return
+}
+
+func (w *Writer) flushPendingBH(key []byte) {
+	if w.pendingBH.length == 0 {
+		return
+	}
+	var separator []byte
+	if len(key) == 0 {
+		separator = w.cmp.Successor(w.comparerScratch[:0], w.dataBlock.prevKey)
+	} else {
+		separator = w.cmp.Separator(w.comparerScratch[:0], w.dataBlock.prevKey, key)
+	}
+	if separator == nil {
+		separator = w.dataBlock.prevKey
+	} else {
+		w.comparerScratch = separator
+	}
+	n := encodeBlockHandle(w.scratch[:20], w.pendingBH)
+	// Append the block handle to the index block.
+	w.indexBlock.append(separator, w.scratch[:n])
+	// Reset prev key of the data block.
+	w.dataBlock.prevKey = w.dataBlock.prevKey[:0]
+	// Clear pending block handle.
+	w.pendingBH = blockHandle{}
+}
+
+func (w *Writer) finishBlock() error {
+	w.dataBlock.finish()
+	bh, err := w.writeBlock(&w.dataBlock.buf, w.compression)
+	if err != nil {
+		return err
+	}
+	w.pendingBH = bh
+	// Reset the data block.
+	w.dataBlock.reset()
+	// Flush the filter block.
+	w.filterBlock.flush(w.offset)
+	return nil
+}
+
+// Append appends key/value pair to the table. The keys passed must
+// be in increasing order.
+//
+// It is safe to modify the contents of the arguments after Append returns.
+func (w *Writer) Append(key, value []byte) error {
+	if w.err != nil {
+		return w.err
+	}
+	if w.nEntries > 0 && w.cmp.Compare(w.dataBlock.prevKey, key) >= 0 {
+		w.err = fmt.Errorf("leveldb/table: Writer: keys are not in increasing order: %q, %q", w.dataBlock.prevKey, key)
+		return w.err
+	}
+
+	w.flushPendingBH(key)
+	// Append key/value pair to the data block.
+	w.dataBlock.append(key, value)
+	// Add key to the filter block.
+	w.filterBlock.add(key)
+
+	// Finish the data block if block size target reached.
+	if w.dataBlock.bytesLen() >= w.blockSize {
+		if err := w.finishBlock(); err != nil {
+			w.err = err
+			return w.err
+		}
+	}
+	w.nEntries++
+	return nil
+}
+
+// BlocksLen returns number of blocks written so far.
+func (w *Writer) BlocksLen() int {
+	n := w.indexBlock.nEntries
+	if w.pendingBH.length > 0 {
+		// Includes the pending block.
+		n++
+	}
+	return n
+}
+
+// EntriesLen returns number of entries added so far.
+func (w *Writer) EntriesLen() int {
+	return w.nEntries
+}
+
+// BytesLen returns number of bytes written so far.
+func (w *Writer) BytesLen() int {
+	return int(w.offset)
+}
+
+// Close will finalize the table. Calling Append is not possible
+// after Close, but calling BlocksLen, EntriesLen and BytesLen
+// is still possible.
+func (w *Writer) Close() error {
+	if w.err != nil {
+		return w.err
+	}
+
+	// Write the last data block. Or empty data block if there
+	// aren't any data blocks at all.
+	if w.dataBlock.nEntries > 0 || w.nEntries == 0 {
+		if err := w.finishBlock(); err != nil {
+			w.err = err
+			return w.err
+		}
+	}
+	w.flushPendingBH(nil)
+
+	// Write the filter block.
+	var filterBH blockHandle
+	w.filterBlock.finish()
+	if buf := &w.filterBlock.buf; buf.Len() > 0 {
+		filterBH, w.err = w.writeBlock(buf, opt.NoCompression)
+		if w.err != nil {
+			return w.err
+		}
+	}
+
+	// Write the metaindex block.
+	if filterBH.length > 0 {
+		key := []byte("filter." + w.filter.Name())
+		n := encodeBlockHandle(w.scratch[:20], filterBH)
+		w.dataBlock.append(key, w.scratch[:n])
+	}
+	w.dataBlock.finish()
+	metaindexBH, err := w.writeBlock(&w.dataBlock.buf, w.compression)
+	if err != nil {
+		w.err = err
+		return w.err
+	}
+
+	// Write the index block.
+	w.indexBlock.finish()
+	indexBH, err := w.writeBlock(&w.indexBlock.buf, w.compression)
+	if err != nil {
+		w.err = err
+		return w.err
+	}
+
+	// Write the table footer.
+	footer := w.scratch[:footerLen]
+	for i := range footer {
+		footer[i] = 0
+	}
+	n := encodeBlockHandle(footer, metaindexBH)
+	encodeBlockHandle(footer[n:], indexBH)
+	copy(footer[footerLen-len(magic):], magic)
+	if _, err := w.writer.Write(footer); err != nil {
+		w.err = err
+		return w.err
+	}
+	w.offset += footerLen
+
+	w.err = errors.New("leveldb/table: writer is closed")
+	return nil
+}
+
+// NewWriter creates a new initialized table writer for the file.
+//
+// Table writer is not safe for concurrent use.
+func NewWriter(f io.Writer, o *opt.Options) *Writer {
+	w := &Writer{
+		writer:          f,
+		cmp:             o.GetComparer(),
+		filter:          o.GetFilter(),
+		compression:     o.GetCompression(),
+		blockSize:       o.GetBlockSize(),
+		comparerScratch: make([]byte, 0),
+	}
+	// data block
+	w.dataBlock.restartInterval = o.GetBlockRestartInterval()
+	// The first 20-bytes are used for encoding block handle.
+	w.dataBlock.scratch = w.scratch[20:]
+	// index block
+	w.indexBlock.restartInterval = 1
+	w.indexBlock.scratch = w.scratch[20:]
+	// filter block
+	if w.filter != nil {
+		w.filterBlock.generator = w.filter.NewGenerator()
+		w.filterBlock.flush(0)
+	}
+	return w
+}

vendor/github.com/syndtr/goleveldb/leveldb/util.go

@@ -0,0 +1,98 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"fmt"
+	"sort"
+
+	"github.com/syndtr/goleveldb/leveldb/storage"
+)
+
+func shorten(str string) string {
+	if len(str) <= 8 {
+		return str
+	}
+	return str[:3] + ".." + str[len(str)-3:]
+}
+
+var bunits = [...]string{"", "Ki", "Mi", "Gi", "Ti"}
+
+func shortenb(bytes int) string {
+	i := 0
+	for ; bytes > 1024 && i < 4; i++ {
+		bytes /= 1024
+	}
+	return fmt.Sprintf("%d%sB", bytes, bunits[i])
+}
+
+func sshortenb(bytes int) string {
+	if bytes == 0 {
+		return "~"
+	}
+	sign := "+"
+	if bytes < 0 {
+		sign = "-"
+		bytes *= -1
+	}
+	i := 0
+	for ; bytes > 1024 && i < 4; i++ {
+		bytes /= 1024
+	}
+	return fmt.Sprintf("%s%d%sB", sign, bytes, bunits[i])
+}
+
+func sint(x int) string {
+	if x == 0 {
+		return "~"
+	}
+	sign := "+"
+	if x < 0 {
+		sign = "-"
+		x *= -1
+	}
+	return fmt.Sprintf("%s%d", sign, x)
+}
+
+func minInt(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+func maxInt(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+
+type fdSorter []storage.FileDesc
+
+func (p fdSorter) Len() int {
+	return len(p)
+}
+
+func (p fdSorter) Less(i, j int) bool {
+	return p[i].Num < p[j].Num
+}
+
+func (p fdSorter) Swap(i, j int) {
+	p[i], p[j] = p[j], p[i]
+}
+
+func sortFds(fds []storage.FileDesc) {
+	sort.Sort(fdSorter(fds))
+}
+
+func ensureBuffer(b []byte, n int) []byte {
+	if cap(b) < n {
+		return make([]byte, n)
+	}
+	return b[:n]
+}

vendor/github.com/syndtr/goleveldb/leveldb/util/buffer.go

@@ -0,0 +1,293 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package util
+
+// This a copy of Go std bytes.Buffer with some modification
+// and some features stripped.
+
+import (
+	"bytes"
+	"io"
+)
+
+// A Buffer is a variable-sized buffer of bytes with Read and Write methods.
+// The zero value for Buffer is an empty buffer ready to use.
+type Buffer struct {
+	buf       []byte   // contents are the bytes buf[off : len(buf)]
+	off       int      // read at &buf[off], write at &buf[len(buf)]
+	bootstrap [64]byte // memory to hold first slice; helps small buffers (Printf) avoid allocation.
+}
+
+// Bytes returns a slice of the contents of the unread portion of the buffer;
+// len(b.Bytes()) == b.Len().  If the caller changes the contents of the
+// returned slice, the contents of the buffer will change provided there
+// are no intervening method calls on the Buffer.
+func (b *Buffer) Bytes() []byte { return b.buf[b.off:] }
+
+// String returns the contents of the unread portion of the buffer
+// as a string.  If the Buffer is a nil pointer, it returns "<nil>".
+func (b *Buffer) String() string {
+	if b == nil {
+		// Special case, useful in debugging.
+		return "<nil>"
+	}
+	return string(b.buf[b.off:])
+}
+
+// Len returns the number of bytes of the unread portion of the buffer;
+// b.Len() == len(b.Bytes()).
+func (b *Buffer) Len() int { return len(b.buf) - b.off }
+
+// Truncate discards all but the first n unread bytes from the buffer.
+// It panics if n is negative or greater than the length of the buffer.
+func (b *Buffer) Truncate(n int) {
+	switch {
+	case n < 0 || n > b.Len():
+		panic("leveldb/util.Buffer: truncation out of range")
+	case n == 0:
+		// Reuse buffer space.
+		b.off = 0
+	}
+	b.buf = b.buf[0 : b.off+n]
+}
+
+// Reset resets the buffer so it has no content.
+// b.Reset() is the same as b.Truncate(0).
+func (b *Buffer) Reset() { b.Truncate(0) }
+
+// grow grows the buffer to guarantee space for n more bytes.
+// It returns the index where bytes should be written.
+// If the buffer can't grow it will panic with bytes.ErrTooLarge.
+func (b *Buffer) grow(n int) int {
+	m := b.Len()
+	// If buffer is empty, reset to recover space.
+	if m == 0 && b.off != 0 {
+		b.Truncate(0)
+	}
+	if len(b.buf)+n > cap(b.buf) {
+		var buf []byte
+		if b.buf == nil && n <= len(b.bootstrap) {
+			buf = b.bootstrap[0:]
+		} else if m+n <= cap(b.buf)/2 {
+			// We can slide things down instead of allocating a new
+			// slice. We only need m+n <= cap(b.buf) to slide, but
+			// we instead let capacity get twice as large so we
+			// don't spend all our time copying.
+			copy(b.buf[:], b.buf[b.off:])
+			buf = b.buf[:m]
+		} else {
+			// not enough space anywhere
+			buf = makeSlice(2*cap(b.buf) + n)
+			copy(buf, b.buf[b.off:])
+		}
+		b.buf = buf
+		b.off = 0
+	}
+	b.buf = b.buf[0 : b.off+m+n]
+	return b.off + m
+}
+
+// Alloc allocs n bytes of slice from the buffer, growing the buffer as
+// needed. If n is negative, Alloc will panic.
+// If the buffer can't grow it will panic with bytes.ErrTooLarge.
+func (b *Buffer) Alloc(n int) []byte {
+	if n < 0 {
+		panic("leveldb/util.Buffer.Alloc: negative count")
+	}
+	m := b.grow(n)
+	return b.buf[m:]
+}
+
+// Grow grows the buffer's capacity, if necessary, to guarantee space for
+// another n bytes. After Grow(n), at least n bytes can be written to the
+// buffer without another allocation.
+// If n is negative, Grow will panic.
+// If the buffer can't grow it will panic with bytes.ErrTooLarge.
+func (b *Buffer) Grow(n int) {
+	if n < 0 {
+		panic("leveldb/util.Buffer.Grow: negative count")
+	}
+	m := b.grow(n)
+	b.buf = b.buf[0:m]
+}
+
+// Write appends the contents of p to the buffer, growing the buffer as
+// needed. The return value n is the length of p; err is always nil. If the
+// buffer becomes too large, Write will panic with bytes.ErrTooLarge.
+func (b *Buffer) Write(p []byte) (n int, err error) {
+	m := b.grow(len(p))
+	return copy(b.buf[m:], p), nil
+}
+
+// MinRead is the minimum slice size passed to a Read call by
+// Buffer.ReadFrom.  As long as the Buffer has at least MinRead bytes beyond
+// what is required to hold the contents of r, ReadFrom will not grow the
+// underlying buffer.
+const MinRead = 512
+
+// ReadFrom reads data from r until EOF and appends it to the buffer, growing
+// the buffer as needed. The return value n is the number of bytes read. Any
+// error except io.EOF encountered during the read is also returned. If the
+// buffer becomes too large, ReadFrom will panic with bytes.ErrTooLarge.
+func (b *Buffer) ReadFrom(r io.Reader) (n int64, err error) {
+	// If buffer is empty, reset to recover space.
+	if b.off >= len(b.buf) {
+		b.Truncate(0)
+	}
+	for {
+		if free := cap(b.buf) - len(b.buf); free < MinRead {
+			// not enough space at end
+			newBuf := b.buf
+			if b.off+free < MinRead {
+				// not enough space using beginning of buffer;
+				// double buffer capacity
+				newBuf = makeSlice(2*cap(b.buf) + MinRead)
+			}
+			copy(newBuf, b.buf[b.off:])
+			b.buf = newBuf[:len(b.buf)-b.off]
+			b.off = 0
+		}
+		m, e := r.Read(b.buf[len(b.buf):cap(b.buf)])
+		b.buf = b.buf[0 : len(b.buf)+m]
+		n += int64(m)
+		if e == io.EOF {
+			break
+		}
+		if e != nil {
+			return n, e
+		}
+	}
+	return n, nil // err is EOF, so return nil explicitly
+}
+
+// makeSlice allocates a slice of size n. If the allocation fails, it panics
+// with bytes.ErrTooLarge.
+func makeSlice(n int) []byte {
+	// If the make fails, give a known error.
+	defer func() {
+		if recover() != nil {
+			panic(bytes.ErrTooLarge)
+		}
+	}()
+	return make([]byte, n)
+}
+
+// WriteTo writes data to w until the buffer is drained or an error occurs.
+// The return value n is the number of bytes written; it always fits into an
+// int, but it is int64 to match the io.WriterTo interface. Any error
+// encountered during the write is also returned.
+func (b *Buffer) WriteTo(w io.Writer) (n int64, err error) {
+	if b.off < len(b.buf) {
+		nBytes := b.Len()
+		m, e := w.Write(b.buf[b.off:])
+		if m > nBytes {
+			panic("leveldb/util.Buffer.WriteTo: invalid Write count")
+		}
+		b.off += m
+		n = int64(m)
+		if e != nil {
+			return n, e
+		}
+		// all bytes should have been written, by definition of
+		// Write method in io.Writer
+		if m != nBytes {
+			return n, io.ErrShortWrite
+		}
+	}
+	// Buffer is now empty; reset.
+	b.Truncate(0)
+	return
+}
+
+// WriteByte appends the byte c to the buffer, growing the buffer as needed.
+// The returned error is always nil, but is included to match bufio.Writer's
+// WriteByte. If the buffer becomes too large, WriteByte will panic with
+// bytes.ErrTooLarge.
+func (b *Buffer) WriteByte(c byte) error {
+	m := b.grow(1)
+	b.buf[m] = c
+	return nil
+}
+
+// Read reads the next len(p) bytes from the buffer or until the buffer
+// is drained.  The return value n is the number of bytes read.  If the
+// buffer has no data to return, err is io.EOF (unless len(p) is zero);
+// otherwise it is nil.
+func (b *Buffer) Read(p []byte) (n int, err error) {
+	if b.off >= len(b.buf) {
+		// Buffer is empty, reset to recover space.
+		b.Truncate(0)
+		if len(p) == 0 {
+			return
+		}
+		return 0, io.EOF
+	}
+	n = copy(p, b.buf[b.off:])
+	b.off += n
+	return
+}
+
+// Next returns a slice containing the next n bytes from the buffer,
+// advancing the buffer as if the bytes had been returned by Read.
+// If there are fewer than n bytes in the buffer, Next returns the entire buffer.
+// The slice is only valid until the next call to a read or write method.
+func (b *Buffer) Next(n int) []byte {
+	m := b.Len()
+	if n > m {
+		n = m
+	}
+	data := b.buf[b.off : b.off+n]
+	b.off += n
+	return data
+}
+
+// ReadByte reads and returns the next byte from the buffer.
+// If no byte is available, it returns error io.EOF.
+func (b *Buffer) ReadByte() (c byte, err error) {
+	if b.off >= len(b.buf) {
+		// Buffer is empty, reset to recover space.
+		b.Truncate(0)
+		return 0, io.EOF
+	}
+	c = b.buf[b.off]
+	b.off++
+	return c, nil
+}
+
+// ReadBytes reads until the first occurrence of delim in the input,
+// returning a slice containing the data up to and including the delimiter.
+// If ReadBytes encounters an error before finding a delimiter,
+// it returns the data read before the error and the error itself (often io.EOF).
+// ReadBytes returns err != nil if and only if the returned data does not end in
+// delim.
+func (b *Buffer) ReadBytes(delim byte) (line []byte, err error) {
+	slice, err := b.readSlice(delim)
+	// return a copy of slice. The buffer's backing array may
+	// be overwritten by later calls.
+	line = append(line, slice...)
+	return
+}
+
+// readSlice is like ReadBytes but returns a reference to internal buffer data.
+func (b *Buffer) readSlice(delim byte) (line []byte, err error) {
+	i := bytes.IndexByte(b.buf[b.off:], delim)
+	end := b.off + i + 1
+	if i < 0 {
+		end = len(b.buf)
+		err = io.EOF
+	}
+	line = b.buf[b.off:end]
+	b.off = end
+	return line, err
+}
+
+// NewBuffer creates and initializes a new Buffer using buf as its initial
+// contents.  It is intended to prepare a Buffer to read existing data.  It
+// can also be used to size the internal buffer for writing. To do that,
+// buf should have the desired capacity but a length of zero.
+//
+// In most cases, new(Buffer) (or just declaring a Buffer variable) is
+// sufficient to initialize a Buffer.
+func NewBuffer(buf []byte) *Buffer { return &Buffer{buf: buf} }

vendor/github.com/syndtr/goleveldb/leveldb/util/buffer_pool.go

@@ -0,0 +1,239 @@
+// Copyright (c) 2014, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package util
+
+import (
+	"fmt"
+	"sync"
+	"sync/atomic"
+	"time"
+)
+
+type buffer struct {
+	b    []byte
+	miss int
+}
+
+// BufferPool is a 'buffer pool'.
+type BufferPool struct {
+	pool      [6]chan []byte
+	size      [5]uint32
+	sizeMiss  [5]uint32
+	sizeHalf  [5]uint32
+	baseline  [4]int
+	baseline0 int
+
+	mu     sync.RWMutex
+	closed bool
+	closeC chan struct{}
+
+	get     uint32
+	put     uint32
+	half    uint32
+	less    uint32
+	equal   uint32
+	greater uint32
+	miss    uint32
+}
+
+func (p *BufferPool) poolNum(n int) int {
+	if n <= p.baseline0 && n > p.baseline0/2 {
+		return 0
+	}
+	for i, x := range p.baseline {
+		if n <= x {
+			return i + 1
+		}
+	}
+	return len(p.baseline) + 1
+}
+
+// Get returns buffer with length of n.
+func (p *BufferPool) Get(n int) []byte {
+	if p == nil {
+		return make([]byte, n)
+	}
+
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+
+	if p.closed {
+		return make([]byte, n)
+	}
+
+	atomic.AddUint32(&p.get, 1)
+
+	poolNum := p.poolNum(n)
+	pool := p.pool[poolNum]
+	if poolNum == 0 {
+		// Fast path.
+		select {
+		case b := <-pool:
+			switch {
+			case cap(b) > n:
+				if cap(b)-n >= n {
+					atomic.AddUint32(&p.half, 1)
+					select {
+					case pool <- b:
+					default:
+					}
+					return make([]byte, n)
+				} else {
+					atomic.AddUint32(&p.less, 1)
+					return b[:n]
+				}
+			case cap(b) == n:
+				atomic.AddUint32(&p.equal, 1)
+				return b[:n]
+			default:
+				atomic.AddUint32(&p.greater, 1)
+			}
+		default:
+			atomic.AddUint32(&p.miss, 1)
+		}
+
+		return make([]byte, n, p.baseline0)
+	} else {
+		sizePtr := &p.size[poolNum-1]
+
+		select {
+		case b := <-pool:
+			switch {
+			case cap(b) > n:
+				if cap(b)-n >= n {
+					atomic.AddUint32(&p.half, 1)
+					sizeHalfPtr := &p.sizeHalf[poolNum-1]
+					if atomic.AddUint32(sizeHalfPtr, 1) == 20 {
+						atomic.StoreUint32(sizePtr, uint32(cap(b)/2))
+						atomic.StoreUint32(sizeHalfPtr, 0)
+					} else {
+						select {
+						case pool <- b:
+						default:
+						}
+					}
+					return make([]byte, n)
+				} else {
+					atomic.AddUint32(&p.less, 1)
+					return b[:n]
+				}
+			case cap(b) == n:
+				atomic.AddUint32(&p.equal, 1)
+				return b[:n]
+			default:
+				atomic.AddUint32(&p.greater, 1)
+				if uint32(cap(b)) >= atomic.LoadUint32(sizePtr) {
+					select {
+					case pool <- b:
+					default:
+					}
+				}
+			}
+		default:
+			atomic.AddUint32(&p.miss, 1)
+		}
+
+		if size := atomic.LoadUint32(sizePtr); uint32(n) > size {
+			if size == 0 {
+				atomic.CompareAndSwapUint32(sizePtr, 0, uint32(n))
+			} else {
+				sizeMissPtr := &p.sizeMiss[poolNum-1]
+				if atomic.AddUint32(sizeMissPtr, 1) == 20 {
+					atomic.StoreUint32(sizePtr, uint32(n))
+					atomic.StoreUint32(sizeMissPtr, 0)
+				}
+			}
+			return make([]byte, n)
+		} else {
+			return make([]byte, n, size)
+		}
+	}
+}
+
+// Put adds given buffer to the pool.
+func (p *BufferPool) Put(b []byte) {
+	if p == nil {
+		return
+	}
+
+	p.mu.RLock()
+	defer p.mu.RUnlock()
+
+	if p.closed {
+		return
+	}
+
+	atomic.AddUint32(&p.put, 1)
+
+	pool := p.pool[p.poolNum(cap(b))]
+	select {
+	case pool <- b:
+	default:
+	}
+
+}
+
+func (p *BufferPool) Close() {
+	if p == nil {
+		return
+	}
+
+	p.mu.Lock()
+	if !p.closed {
+		p.closed = true
+		p.closeC <- struct{}{}
+	}
+	p.mu.Unlock()
+}
+
+func (p *BufferPool) String() string {
+	if p == nil {
+		return "<nil>"
+	}
+
+	return fmt.Sprintf("BufferPool{B·%d Z·%v Zm·%v Zh·%v G·%d P·%d H·%d <·%d =·%d >·%d M·%d}",
+		p.baseline0, p.size, p.sizeMiss, p.sizeHalf, p.get, p.put, p.half, p.less, p.equal, p.greater, p.miss)
+}
+
+func (p *BufferPool) drain() {
+	ticker := time.NewTicker(2 * time.Second)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-ticker.C:
+			for _, ch := range p.pool {
+				select {
+				case <-ch:
+				default:
+				}
+			}
+		case <-p.closeC:
+			close(p.closeC)
+			for _, ch := range p.pool {
+				close(ch)
+			}
+			return
+		}
+	}
+}
+
+// NewBufferPool creates a new initialized 'buffer pool'.
+func NewBufferPool(baseline int) *BufferPool {
+	if baseline <= 0 {
+		panic("baseline can't be <= 0")
+	}
+	p := &BufferPool{
+		baseline0: baseline,
+		baseline:  [...]int{baseline / 4, baseline / 2, baseline * 2, baseline * 4},
+		closeC:    make(chan struct{}, 1),
+	}
+	for i, cap := range []int{2, 2, 4, 4, 2, 1} {
+		p.pool[i] = make(chan []byte, cap)
+	}
+	go p.drain()
+	return p
+}

vendor/github.com/syndtr/goleveldb/leveldb/util/crc32.go

@@ -0,0 +1,30 @@
+// Copyright 2011 The LevelDB-Go Authors. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package util
+
+import (
+	"hash/crc32"
+)
+
+var table = crc32.MakeTable(crc32.Castagnoli)
+
+// CRC is a CRC-32 checksum computed using Castagnoli's polynomial.
+type CRC uint32
+
+// NewCRC creates a new crc based on the given bytes.
+func NewCRC(b []byte) CRC {
+	return CRC(0).Update(b)
+}
+
+// Update updates the crc with the given bytes.
+func (c CRC) Update(b []byte) CRC {
+	return CRC(crc32.Update(uint32(c), table, b))
+}
+
+// Value returns a masked crc.
+func (c CRC) Value() uint32 {
+	return uint32(c>>15|c<<17) + 0xa282ead8
+}

vendor/github.com/syndtr/goleveldb/leveldb/util/hash.go

@@ -0,0 +1,48 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package util
+
+import (
+	"encoding/binary"
+)
+
+// Hash return hash of the given data.
+func Hash(data []byte, seed uint32) uint32 {
+	// Similar to murmur hash
+	const (
+		m = uint32(0xc6a4a793)
+		r = uint32(24)
+	)
+	var (
+		h = seed ^ (uint32(len(data)) * m)
+		i int
+	)
+
+	for n := len(data) - len(data)%4; i < n; i += 4 {
+		h += binary.LittleEndian.Uint32(data[i:])
+		h *= m
+		h ^= (h >> 16)
+	}
+
+	switch len(data) - i {
+	default:
+		panic("not reached")
+	case 3:
+		h += uint32(data[i+2]) << 16
+		fallthrough
+	case 2:
+		h += uint32(data[i+1]) << 8
+		fallthrough
+	case 1:
+		h += uint32(data[i])
+		h *= m
+		h ^= (h >> r)
+	case 0:
+	}
+
+	return h
+}

vendor/github.com/syndtr/goleveldb/leveldb/util/range.go

@@ -0,0 +1,32 @@
+// Copyright (c) 2014, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package util
+
+// Range is a key range.
+type Range struct {
+	// Start of the key range, include in the range.
+	Start []byte
+
+	// Limit of the key range, not include in the range.
+	Limit []byte
+}
+
+// BytesPrefix returns key range that satisfy the given prefix.
+// This only applicable for the standard 'bytes comparer'.
+func BytesPrefix(prefix []byte) *Range {
+	var limit []byte
+	for i := len(prefix) - 1; i >= 0; i-- {
+		c := prefix[i]
+		if c < 0xff {
+			limit = make([]byte, i+1)
+			copy(limit, prefix)
+			limit[i] = c + 1
+			break
+		}
+	}
+	return &Range{prefix, limit}
+}

vendor/github.com/syndtr/goleveldb/leveldb/util/util.go

@@ -0,0 +1,73 @@
+// Copyright (c) 2013, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Package util provides utilities used throughout leveldb.
+package util
+
+import (
+	"errors"
+)
+
+var (
+	ErrReleased    = errors.New("leveldb: resource already relesed")
+	ErrHasReleaser = errors.New("leveldb: releaser already defined")
+)
+
+// Releaser is the interface that wraps the basic Release method.
+type Releaser interface {
+	// Release releases associated resources. Release should always success
+	// and can be called multiple times without causing error.
+	Release()
+}
+
+// ReleaseSetter is the interface that wraps the basic SetReleaser method.
+type ReleaseSetter interface {
+	// SetReleaser associates the given releaser to the resources. The
+	// releaser will be called once coresponding resources released.
+	// Calling SetReleaser with nil will clear the releaser.
+	//
+	// This will panic if a releaser already present or coresponding
+	// resource is already released. Releaser should be cleared first
+	// before assigned a new one.
+	SetReleaser(releaser Releaser)
+}
+
+// BasicReleaser provides basic implementation of Releaser and ReleaseSetter.
+type BasicReleaser struct {
+	releaser Releaser
+	released bool
+}
+
+// Released returns whether Release method already called.
+func (r *BasicReleaser) Released() bool {
+	return r.released
+}
+
+// Release implements Releaser.Release.
+func (r *BasicReleaser) Release() {
+	if !r.released {
+		if r.releaser != nil {
+			r.releaser.Release()
+			r.releaser = nil
+		}
+		r.released = true
+	}
+}
+
+// SetReleaser implements ReleaseSetter.SetReleaser.
+func (r *BasicReleaser) SetReleaser(releaser Releaser) {
+	if r.released {
+		panic(ErrReleased)
+	}
+	if r.releaser != nil && releaser != nil {
+		panic(ErrHasReleaser)
+	}
+	r.releaser = releaser
+}
+
+type NoopReleaser struct{}
+
+func (NoopReleaser) Release() {}

vendor/github.com/syndtr/goleveldb/leveldb/version.go

@@ -0,0 +1,528 @@
+// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
+// All rights reserved.
+//
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package leveldb
+
+import (
+	"fmt"
+	"sync/atomic"
+	"unsafe"
+
+	"github.com/syndtr/goleveldb/leveldb/iterator"
+	"github.com/syndtr/goleveldb/leveldb/opt"
+	"github.com/syndtr/goleveldb/leveldb/util"
+)
+
+type tSet struct {
+	level int
+	table *tFile
+}
+
+type version struct {
+	s *session
+
+	levels []tFiles
+
+	// Level that should be compacted next and its compaction score.
+	// Score < 1 means compaction is not strictly needed. These fields
+	// are initialized by computeCompaction()
+	cLevel int
+	cScore float64
+
+	cSeek unsafe.Pointer
+
+	closing  bool
+	ref      int
+	released bool
+}
+
+func newVersion(s *session) *version {
+	return &version{s: s}
+}
+
+func (v *version) incref() {
+	if v.released {
+		panic("already released")
+	}
+
+	v.ref++
+	if v.ref == 1 {
+		// Incr file ref.
+		for _, tt := range v.levels {
+			for _, t := range tt {
+				v.s.addFileRef(t.fd, 1)
+			}
+		}
+	}
+}
+
+func (v *version) releaseNB() {
+	v.ref--
+	if v.ref > 0 {
+		return
+	} else if v.ref < 0 {
+		panic("negative version ref")
+	}
+
+	for _, tt := range v.levels {
+		for _, t := range tt {
+			if v.s.addFileRef(t.fd, -1) == 0 {
+				v.s.tops.remove(t)
+			}
+		}
+	}
+
+	v.released = true
+}
+
+func (v *version) release() {
+	v.s.vmu.Lock()
+	v.releaseNB()
+	v.s.vmu.Unlock()
+}
+
+func (v *version) walkOverlapping(aux tFiles, ikey internalKey, f func(level int, t *tFile) bool, lf func(level int) bool) {
+	ukey := ikey.ukey()
+
+	// Aux level.
+	if aux != nil {
+		for _, t := range aux {
+			if t.overlaps(v.s.icmp, ukey, ukey) {
+				if !f(-1, t) {
+					return
+				}
+			}
+		}
+
+		if lf != nil && !lf(-1) {
+			return
+		}
+	}
+
+	// Walk tables level-by-level.
+	for level, tables := range v.levels {
+		if len(tables) == 0 {
+			continue
+		}
+
+		if level == 0 {
+			// Level-0 files may overlap each other. Find all files that
+			// overlap ukey.
+			for _, t := range tables {
+				if t.overlaps(v.s.icmp, ukey, ukey) {
+					if !f(level, t) {
+						return
+					}
+				}
+			}
+		} else {
+			if i := tables.searchMax(v.s.icmp, ikey); i < len(tables) {
+				t := tables[i]
+				if v.s.icmp.uCompare(ukey, t.imin.ukey()) >= 0 {
+					if !f(level, t) {
+						return
+					}
+				}
+			}
+		}
+
+		if lf != nil && !lf(level) {
+			return
+		}
+	}
+}
+
+func (v *version) get(aux tFiles, ikey internalKey, ro *opt.ReadOptions, noValue bool) (value []byte, tcomp bool, err error) {
+	if v.closing {
+		return nil, false, ErrClosed
+	}
+
+	ukey := ikey.ukey()
+
+	var (
+		tset  *tSet
+		tseek bool
+
+		// Level-0.
+		zfound bool
+		zseq   uint64
+		zkt    keyType
+		zval   []byte
+	)
+
+	err = ErrNotFound
+
+	// Since entries never hop across level, finding key/value
+	// in smaller level make later levels irrelevant.
+	v.walkOverlapping(aux, ikey, func(level int, t *tFile) bool {
+		if level >= 0 && !tseek {
+			if tset == nil {
+				tset = &tSet{level, t}
+			} else {
+				tseek = true
+			}
+		}
+
+		var (
+			fikey, fval []byte
+			ferr        error
+		)
+		if noValue {
+			fikey, ferr = v.s.tops.findKey(t, ikey, ro)
+		} else {
+			fikey, fval, ferr = v.s.tops.find(t, ikey, ro)
+		}
+
+		switch ferr {
+		case nil:
+		case ErrNotFound:
+			return true
+		default:
+			err = ferr
+			return false
+		}
+
+		if fukey, fseq, fkt, fkerr := parseInternalKey(fikey); fkerr == nil {
+			if v.s.icmp.uCompare(ukey, fukey) == 0 {
+				// Level <= 0 may overlaps each-other.
+				if level <= 0 {
+					if fseq >= zseq {
+						zfound = true
+						zseq = fseq
+						zkt = fkt
+						zval = fval
+					}
+				} else {
+					switch fkt {
+					case keyTypeVal:
+						value = fval
+						err = nil
+					case keyTypeDel:
+					default:
+						panic("leveldb: invalid internalKey type")
+					}
+					return false
+				}
+			}
+		} else {
+			err = fkerr
+			return false
+		}
+
+		return true
+	}, func(level int) bool {
+		if zfound {
+			switch zkt {
+			case keyTypeVal:
+				value = zval
+				err = nil
+			case keyTypeDel:
+			default:
+				panic("leveldb: invalid internalKey type")
+			}
+			return false
+		}
+
+		return true
+	})
+
+	if tseek && tset.table.consumeSeek() <= 0 {
+		tcomp = atomic.CompareAndSwapPointer(&v.cSeek, nil, unsafe.Pointer(tset))
+	}
+
+	return
+}
+
+func (v *version) sampleSeek(ikey internalKey) (tcomp bool) {
+	var tset *tSet
+
+	v.walkOverlapping(nil, ikey, func(level int, t *tFile) bool {
+		if tset == nil {
+			tset = &tSet{level, t}
+			return true
+		}
+		if tset.table.consumeSeek() <= 0 {
+			tcomp = atomic.CompareAndSwapPointer(&v.cSeek, nil, unsafe.Pointer(tset))
+		}
+		return false
+	}, nil)
+
+	return
+}
+
+func (v *version) getIterators(slice *util.Range, ro *opt.ReadOptions) (its []iterator.Iterator) {
+	strict := opt.GetStrict(v.s.o.Options, ro, opt.StrictReader)
+	for level, tables := range v.levels {
+		if level == 0 {
+			// Merge all level zero files together since they may overlap.
+			for _, t := range tables {
+				its = append(its, v.s.tops.newIterator(t, slice, ro))
+			}
+		} else if len(tables) != 0 {
+			its = append(its, iterator.NewIndexedIterator(tables.newIndexIterator(v.s.tops, v.s.icmp, slice, ro), strict))
+		}
+	}
+	return
+}
+
+func (v *version) newStaging() *versionStaging {
+	return &versionStaging{base: v}
+}
+
+// Spawn a new version based on this version.
+func (v *version) spawn(r *sessionRecord) *version {
+	staging := v.newStaging()
+	staging.commit(r)
+	return staging.finish()
+}
+
+func (v *version) fillRecord(r *sessionRecord) {
+	for level, tables := range v.levels {
+		for _, t := range tables {
+			r.addTableFile(level, t)
+		}
+	}
+}
+
+func (v *version) tLen(level int) int {
+	if level < len(v.levels) {
+		return len(v.levels[level])
+	}
+	return 0
+}
+
+func (v *version) offsetOf(ikey internalKey) (n int64, err error) {
+	for level, tables := range v.levels {
+		for _, t := range tables {
+			if v.s.icmp.Compare(t.imax, ikey) <= 0 {
+				// Entire file is before "ikey", so just add the file size
+				n += t.size
+			} else if v.s.icmp.Compare(t.imin, ikey) > 0 {
+				// Entire file is after "ikey", so ignore
+				if level > 0 {
+					// Files other than level 0 are sorted by meta->min, so
+					// no further files in this level will contain data for
+					// "ikey".
+					break
+				}
+			} else {
+				// "ikey" falls in the range for this table. Add the
+				// approximate offset of "ikey" within the table.
+				if m, err := v.s.tops.offsetOf(t, ikey); err == nil {
+					n += m
+				} else {
+					return 0, err
+				}
+			}
+		}
+	}
+
+	return
+}
+
+func (v *version) pickMemdbLevel(umin, umax []byte, maxLevel int) (level int) {
+	if maxLevel > 0 {
+		if len(v.levels) == 0 {
+			return maxLevel
+		}
+		if !v.levels[0].overlaps(v.s.icmp, umin, umax, true) {
+			var overlaps tFiles
+			for ; level < maxLevel; level++ {
+				if pLevel := level + 1; pLevel >= len(v.levels) {
+					return maxLevel
+				} else if v.levels[pLevel].overlaps(v.s.icmp, umin, umax, false) {
+					break
+				}
+				if gpLevel := level + 2; gpLevel < len(v.levels) {
+					overlaps = v.levels[gpLevel].getOverlaps(overlaps, v.s.icmp, umin, umax, false)
+					if overlaps.size() > int64(v.s.o.GetCompactionGPOverlaps(level)) {
+						break
+					}
+				}
+			}
+		}
+	}
+	return
+}
+
+func (v *version) computeCompaction() {
+	// Precomputed best level for next compaction
+	bestLevel := int(-1)
+	bestScore := float64(-1)
+
+	statFiles := make([]int, len(v.levels))
+	statSizes := make([]string, len(v.levels))
+	statScore := make([]string, len(v.levels))
+	statTotSize := int64(0)
+
+	for level, tables := range v.levels {
+		var score float64
+		size := tables.size()
+		if level == 0 {
+			// We treat level-0 specially by bounding the number of files
+			// instead of number of bytes for two reasons:
+			//
+			// (1) With larger write-buffer sizes, it is nice not to do too
+			// many level-0 compaction.
+			//
+			// (2) The files in level-0 are merged on every read and
+			// therefore we wish to avoid too many files when the individual
+			// file size is small (perhaps because of a small write-buffer
+			// setting, or very high compression ratios, or lots of
+			// overwrites/deletions).
+			score = float64(len(tables)) / float64(v.s.o.GetCompactionL0Trigger())
+		} else {
+			score = float64(size) / float64(v.s.o.GetCompactionTotalSize(level))
+		}
+
+		if score > bestScore {
+			bestLevel = level
+			bestScore = score
+		}
+
+		statFiles[level] = len(tables)
+		statSizes[level] = shortenb(int(size))
+		statScore[level] = fmt.Sprintf("%.2f", score)
+		statTotSize += size
+	}
+
+	v.cLevel = bestLevel
+	v.cScore = bestScore
+
+	v.s.logf("version@stat F·%v S·%s%v Sc·%v", statFiles, shortenb(int(statTotSize)), statSizes, statScore)
+}
+
+func (v *version) needCompaction() bool {
+	return v.cScore >= 1 || atomic.LoadPointer(&v.cSeek) != nil
+}
+
+type tablesScratch struct {
+	added   map[int64]atRecord
+	deleted map[int64]struct{}
+}
+
+type versionStaging struct {
+	base   *version
+	levels []tablesScratch
+}
+
+func (p *versionStaging) getScratch(level int) *tablesScratch {
+	if level >= len(p.levels) {
+		newLevels := make([]tablesScratch, level+1)
+		copy(newLevels, p.levels)
+		p.levels = newLevels
+	}
+	return &(p.levels[level])
+}
+
+func (p *versionStaging) commit(r *sessionRecord) {
+	// Deleted tables.
+	for _, r := range r.deletedTables {
+		scratch := p.getScratch(r.level)
+		if r.level < len(p.base.levels) && len(p.base.levels[r.level]) > 0 {
+			if scratch.deleted == nil {
+				scratch.deleted = make(map[int64]struct{})
+			}
+			scratch.deleted[r.num] = struct{}{}
+		}
+		if scratch.added != nil {
+			delete(scratch.added, r.num)
+		}
+	}
+
+	// New tables.
+	for _, r := range r.addedTables {
+		scratch := p.getScratch(r.level)
+		if scratch.added == nil {
+			scratch.added = make(map[int64]atRecord)
+		}
+		scratch.added[r.num] = r
+		if scratch.deleted != nil {
+			delete(scratch.deleted, r.num)
+		}
+	}
+}
+
+func (p *versionStaging) finish() *version {
+	// Build new version.
+	nv := newVersion(p.base.s)
+	numLevel := len(p.levels)
+	if len(p.base.levels) > numLevel {
+		numLevel = len(p.base.levels)
+	}
+	nv.levels = make([]tFiles, numLevel)
+	for level := 0; level < numLevel; level++ {
+		var baseTabels tFiles
+		if level < len(p.base.levels) {
+			baseTabels = p.base.levels[level]
+		}
+
+		if level < len(p.levels) {
+			scratch := p.levels[level]
+
+			var nt tFiles
+			// Prealloc list if possible.
+			if n := len(baseTabels) + len(scratch.added) - len(scratch.deleted); n > 0 {
+				nt = make(tFiles, 0, n)
+			}
+
+			// Base tables.
+			for _, t := range baseTabels {
+				if _, ok := scratch.deleted[t.fd.Num]; ok {
+					continue
+				}
+				if _, ok := scratch.added[t.fd.Num]; ok {
+					continue
+				}
+				nt = append(nt, t)
+			}
+
+			// New tables.
+			for _, r := range scratch.added {
+				nt = append(nt, tableFileFromRecord(r))
+			}
+
+			if len(nt) != 0 {
+				// Sort tables.
+				if level == 0 {
+					nt.sortByNum()
+				} else {
+					nt.sortByKey(p.base.s.icmp)
+				}
+
+				nv.levels[level] = nt
+			}
+		} else {
+			nv.levels[level] = baseTabels
+		}
+	}
+
+	// Trim levels.
+	n := len(nv.levels)
+	for ; n > 0 && nv.levels[n-1] == nil; n-- {
+	}
+	nv.levels = nv.levels[:n]
+
+	// Compute compaction score for new version.
+	nv.computeCompaction()
+
+	return nv
+}
+
+type versionReleaser struct {
+	v    *version
+	once bool
+}
+
+func (vr *versionReleaser) Release() {
+	v := vr.v
+	v.s.vmu.Lock()
+	if !vr.once {
+		v.releaseNB()
+		vr.once = true
+	}
+	v.s.vmu.Unlock()
+}

vendor/modules.txt

@@ -7,6 +7,9 @@ github.com/gofiber/fiber/v2
 github.com/gofiber/fiber/v2/internal/schema
 github.com/gofiber/fiber/v2/log
 github.com/gofiber/fiber/v2/utils
+# github.com/golang/snappy v0.0.4
+## explicit
+github.com/golang/snappy
 # github.com/google/uuid v1.4.0
 ## explicit
 github.com/google/uuid
@@ -27,6 +30,20 @@ github.com/mattn/go-runewidth
 # github.com/rivo/uniseg v0.4.4
 ## explicit; go 1.18
 github.com/rivo/uniseg
+# github.com/syndtr/goleveldb v1.0.0
+## explicit
+github.com/syndtr/goleveldb/leveldb
+github.com/syndtr/goleveldb/leveldb/cache
+github.com/syndtr/goleveldb/leveldb/comparer
+github.com/syndtr/goleveldb/leveldb/errors
+github.com/syndtr/goleveldb/leveldb/filter
+github.com/syndtr/goleveldb/leveldb/iterator
+github.com/syndtr/goleveldb/leveldb/journal
+github.com/syndtr/goleveldb/leveldb/memdb
+github.com/syndtr/goleveldb/leveldb/opt
+github.com/syndtr/goleveldb/leveldb/storage
+github.com/syndtr/goleveldb/leveldb/table
+github.com/syndtr/goleveldb/leveldb/util
 # github.com/valyala/bytebufferpool v1.0.0
 ## explicit
 github.com/valyala/bytebufferpool