986f076276
Add a new generic container registry client via a new `container` package. Use this to create a command line utility as well as a new upload target for container registries. The code uses the github.com/containers/* project and packages to interact with container registires that is also used by skopeo, podman et al. One if the dependencies is `proglottis/gpgme` that is using cgo to bind libgpgme, so we have to add the corresponding devel package to the BuildRequires as well as installing it on CI. Checks will follow later via an integration test.
911 lines
25 KiB
Go
911 lines
25 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Copyright (c) 2015 Klaus Post
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package flate
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import (
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"encoding/binary"
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"fmt"
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"io"
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"math"
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)
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const (
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NoCompression = 0
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BestSpeed = 1
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BestCompression = 9
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DefaultCompression = -1
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// HuffmanOnly disables Lempel-Ziv match searching and only performs Huffman
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// entropy encoding. This mode is useful in compressing data that has
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// already been compressed with an LZ style algorithm (e.g. Snappy or LZ4)
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// that lacks an entropy encoder. Compression gains are achieved when
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// certain bytes in the input stream occur more frequently than others.
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//
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// Note that HuffmanOnly produces a compressed output that is
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// RFC 1951 compliant. That is, any valid DEFLATE decompressor will
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// continue to be able to decompress this output.
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HuffmanOnly = -2
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ConstantCompression = HuffmanOnly // compatibility alias.
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logWindowSize = 15
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windowSize = 1 << logWindowSize
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windowMask = windowSize - 1
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logMaxOffsetSize = 15 // Standard DEFLATE
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minMatchLength = 4 // The smallest match that the compressor looks for
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maxMatchLength = 258 // The longest match for the compressor
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minOffsetSize = 1 // The shortest offset that makes any sense
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// The maximum number of tokens we will encode at the time.
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// Smaller sizes usually creates less optimal blocks.
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// Bigger can make context switching slow.
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// We use this for levels 7-9, so we make it big.
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maxFlateBlockTokens = 1 << 15
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maxStoreBlockSize = 65535
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hashBits = 17 // After 17 performance degrades
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hashSize = 1 << hashBits
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hashMask = (1 << hashBits) - 1
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hashShift = (hashBits + minMatchLength - 1) / minMatchLength
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maxHashOffset = 1 << 28
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skipNever = math.MaxInt32
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debugDeflate = false
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)
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type compressionLevel struct {
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good, lazy, nice, chain, fastSkipHashing, level int
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}
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// Compression levels have been rebalanced from zlib deflate defaults
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// to give a bigger spread in speed and compression.
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// See https://blog.klauspost.com/rebalancing-deflate-compression-levels/
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var levels = []compressionLevel{
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{}, // 0
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// Level 1-6 uses specialized algorithm - values not used
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{0, 0, 0, 0, 0, 1},
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{0, 0, 0, 0, 0, 2},
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{0, 0, 0, 0, 0, 3},
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{0, 0, 0, 0, 0, 4},
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{0, 0, 0, 0, 0, 5},
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{0, 0, 0, 0, 0, 6},
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// Levels 7-9 use increasingly more lazy matching
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// and increasingly stringent conditions for "good enough".
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{8, 12, 16, 24, skipNever, 7},
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{16, 30, 40, 64, skipNever, 8},
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{32, 258, 258, 1024, skipNever, 9},
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}
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// advancedState contains state for the advanced levels, with bigger hash tables, etc.
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type advancedState struct {
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// deflate state
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length int
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offset int
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maxInsertIndex int
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// Input hash chains
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// hashHead[hashValue] contains the largest inputIndex with the specified hash value
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// If hashHead[hashValue] is within the current window, then
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// hashPrev[hashHead[hashValue] & windowMask] contains the previous index
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// with the same hash value.
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chainHead int
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hashHead [hashSize]uint32
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hashPrev [windowSize]uint32
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hashOffset int
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// input window: unprocessed data is window[index:windowEnd]
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index int
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estBitsPerByte int
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hashMatch [maxMatchLength + minMatchLength]uint32
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hash uint32
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ii uint16 // position of last match, intended to overflow to reset.
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}
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type compressor struct {
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compressionLevel
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h *huffmanEncoder
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w *huffmanBitWriter
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// compression algorithm
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fill func(*compressor, []byte) int // copy data to window
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step func(*compressor) // process window
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window []byte
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windowEnd int
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blockStart int // window index where current tokens start
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err error
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// queued output tokens
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tokens tokens
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fast fastEnc
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state *advancedState
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sync bool // requesting flush
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byteAvailable bool // if true, still need to process window[index-1].
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}
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func (d *compressor) fillDeflate(b []byte) int {
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s := d.state
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if s.index >= 2*windowSize-(minMatchLength+maxMatchLength) {
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// shift the window by windowSize
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copy(d.window[:], d.window[windowSize:2*windowSize])
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s.index -= windowSize
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d.windowEnd -= windowSize
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if d.blockStart >= windowSize {
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d.blockStart -= windowSize
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} else {
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d.blockStart = math.MaxInt32
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}
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s.hashOffset += windowSize
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if s.hashOffset > maxHashOffset {
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delta := s.hashOffset - 1
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s.hashOffset -= delta
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s.chainHead -= delta
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// Iterate over slices instead of arrays to avoid copying
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// the entire table onto the stack (Issue #18625).
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for i, v := range s.hashPrev[:] {
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if int(v) > delta {
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s.hashPrev[i] = uint32(int(v) - delta)
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} else {
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s.hashPrev[i] = 0
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}
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}
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for i, v := range s.hashHead[:] {
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if int(v) > delta {
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s.hashHead[i] = uint32(int(v) - delta)
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} else {
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s.hashHead[i] = 0
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}
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}
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}
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}
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n := copy(d.window[d.windowEnd:], b)
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d.windowEnd += n
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return n
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}
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func (d *compressor) writeBlock(tok *tokens, index int, eof bool) error {
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if index > 0 || eof {
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var window []byte
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if d.blockStart <= index {
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window = d.window[d.blockStart:index]
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}
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d.blockStart = index
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//d.w.writeBlock(tok, eof, window)
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d.w.writeBlockDynamic(tok, eof, window, d.sync)
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return d.w.err
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}
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return nil
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}
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// writeBlockSkip writes the current block and uses the number of tokens
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// to determine if the block should be stored on no matches, or
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// only huffman encoded.
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func (d *compressor) writeBlockSkip(tok *tokens, index int, eof bool) error {
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if index > 0 || eof {
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if d.blockStart <= index {
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window := d.window[d.blockStart:index]
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// If we removed less than a 64th of all literals
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// we huffman compress the block.
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if int(tok.n) > len(window)-int(tok.n>>6) {
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d.w.writeBlockHuff(eof, window, d.sync)
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} else {
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// Write a dynamic huffman block.
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d.w.writeBlockDynamic(tok, eof, window, d.sync)
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}
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} else {
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d.w.writeBlock(tok, eof, nil)
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}
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d.blockStart = index
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return d.w.err
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}
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return nil
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}
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// fillWindow will fill the current window with the supplied
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// dictionary and calculate all hashes.
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// This is much faster than doing a full encode.
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// Should only be used after a start/reset.
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func (d *compressor) fillWindow(b []byte) {
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// Do not fill window if we are in store-only or huffman mode.
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if d.level <= 0 {
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return
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}
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if d.fast != nil {
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// encode the last data, but discard the result
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if len(b) > maxMatchOffset {
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b = b[len(b)-maxMatchOffset:]
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}
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d.fast.Encode(&d.tokens, b)
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d.tokens.Reset()
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return
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}
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s := d.state
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// If we are given too much, cut it.
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if len(b) > windowSize {
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b = b[len(b)-windowSize:]
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}
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// Add all to window.
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n := copy(d.window[d.windowEnd:], b)
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// Calculate 256 hashes at the time (more L1 cache hits)
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loops := (n + 256 - minMatchLength) / 256
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for j := 0; j < loops; j++ {
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startindex := j * 256
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end := startindex + 256 + minMatchLength - 1
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if end > n {
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end = n
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}
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tocheck := d.window[startindex:end]
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dstSize := len(tocheck) - minMatchLength + 1
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if dstSize <= 0 {
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continue
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}
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dst := s.hashMatch[:dstSize]
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bulkHash4(tocheck, dst)
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var newH uint32
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for i, val := range dst {
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di := i + startindex
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newH = val & hashMask
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// Get previous value with the same hash.
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// Our chain should point to the previous value.
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s.hashPrev[di&windowMask] = s.hashHead[newH]
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// Set the head of the hash chain to us.
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s.hashHead[newH] = uint32(di + s.hashOffset)
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}
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s.hash = newH
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}
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// Update window information.
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d.windowEnd += n
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s.index = n
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}
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// Try to find a match starting at index whose length is greater than prevSize.
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// We only look at chainCount possibilities before giving up.
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// pos = s.index, prevHead = s.chainHead-s.hashOffset, prevLength=minMatchLength-1, lookahead
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func (d *compressor) findMatch(pos int, prevHead int, lookahead int) (length, offset int, ok bool) {
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minMatchLook := maxMatchLength
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if lookahead < minMatchLook {
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minMatchLook = lookahead
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}
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win := d.window[0 : pos+minMatchLook]
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// We quit when we get a match that's at least nice long
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nice := len(win) - pos
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if d.nice < nice {
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nice = d.nice
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}
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// If we've got a match that's good enough, only look in 1/4 the chain.
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tries := d.chain
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length = minMatchLength - 1
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wEnd := win[pos+length]
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wPos := win[pos:]
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minIndex := pos - windowSize
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if minIndex < 0 {
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minIndex = 0
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}
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offset = 0
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cGain := 0
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if d.chain < 100 {
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for i := prevHead; tries > 0; tries-- {
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if wEnd == win[i+length] {
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n := matchLen(win[i:i+minMatchLook], wPos)
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if n > length {
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length = n
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offset = pos - i
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ok = true
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if n >= nice {
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// The match is good enough that we don't try to find a better one.
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break
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}
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wEnd = win[pos+n]
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}
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}
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if i <= minIndex {
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// hashPrev[i & windowMask] has already been overwritten, so stop now.
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break
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}
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i = int(d.state.hashPrev[i&windowMask]) - d.state.hashOffset
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if i < minIndex {
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break
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}
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}
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return
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}
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// Some like it higher (CSV), some like it lower (JSON)
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const baseCost = 6
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// Base is 4 bytes at with an additional cost.
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// Matches must be better than this.
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for i := prevHead; tries > 0; tries-- {
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if wEnd == win[i+length] {
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n := matchLen(win[i:i+minMatchLook], wPos)
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if n > length {
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// Calculate gain. Estimate
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newGain := d.h.bitLengthRaw(wPos[:n]) - int(offsetExtraBits[offsetCode(uint32(pos-i))]) - baseCost - int(lengthExtraBits[lengthCodes[(n-3)&255]])
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//fmt.Println(n, "gain:", newGain, "prev:", cGain, "raw:", d.h.bitLengthRaw(wPos[:n]))
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if newGain > cGain {
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length = n
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offset = pos - i
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cGain = newGain
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ok = true
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if n >= nice {
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// The match is good enough that we don't try to find a better one.
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break
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}
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wEnd = win[pos+n]
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}
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}
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}
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if i <= minIndex {
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// hashPrev[i & windowMask] has already been overwritten, so stop now.
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break
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}
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i = int(d.state.hashPrev[i&windowMask]) - d.state.hashOffset
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if i < minIndex {
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break
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}
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}
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return
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}
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func (d *compressor) writeStoredBlock(buf []byte) error {
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if d.w.writeStoredHeader(len(buf), false); d.w.err != nil {
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return d.w.err
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}
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d.w.writeBytes(buf)
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return d.w.err
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}
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// hash4 returns a hash representation of the first 4 bytes
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// of the supplied slice.
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// The caller must ensure that len(b) >= 4.
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func hash4(b []byte) uint32 {
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return hash4u(binary.LittleEndian.Uint32(b), hashBits)
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}
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// bulkHash4 will compute hashes using the same
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// algorithm as hash4
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func bulkHash4(b []byte, dst []uint32) {
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if len(b) < 4 {
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return
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}
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hb := binary.LittleEndian.Uint32(b)
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dst[0] = hash4u(hb, hashBits)
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end := len(b) - 4 + 1
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for i := 1; i < end; i++ {
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hb = (hb >> 8) | uint32(b[i+3])<<24
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dst[i] = hash4u(hb, hashBits)
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}
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}
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func (d *compressor) initDeflate() {
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d.window = make([]byte, 2*windowSize)
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d.byteAvailable = false
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d.err = nil
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if d.state == nil {
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return
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}
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s := d.state
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s.index = 0
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s.hashOffset = 1
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s.length = minMatchLength - 1
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s.offset = 0
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s.hash = 0
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s.chainHead = -1
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}
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// deflateLazy is the same as deflate, but with d.fastSkipHashing == skipNever,
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// meaning it always has lazy matching on.
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func (d *compressor) deflateLazy() {
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s := d.state
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// Sanity enables additional runtime tests.
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// It's intended to be used during development
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// to supplement the currently ad-hoc unit tests.
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const sanity = debugDeflate
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if d.windowEnd-s.index < minMatchLength+maxMatchLength && !d.sync {
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return
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}
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if d.windowEnd != s.index && d.chain > 100 {
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// Get literal huffman coder.
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if d.h == nil {
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d.h = newHuffmanEncoder(maxFlateBlockTokens)
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}
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var tmp [256]uint16
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for _, v := range d.window[s.index:d.windowEnd] {
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tmp[v]++
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}
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d.h.generate(tmp[:], 15)
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}
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s.maxInsertIndex = d.windowEnd - (minMatchLength - 1)
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if s.index < s.maxInsertIndex {
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s.hash = hash4(d.window[s.index:])
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}
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for {
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if sanity && s.index > d.windowEnd {
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panic("index > windowEnd")
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}
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lookahead := d.windowEnd - s.index
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if lookahead < minMatchLength+maxMatchLength {
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if !d.sync {
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return
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}
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if sanity && s.index > d.windowEnd {
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panic("index > windowEnd")
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}
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if lookahead == 0 {
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// Flush current output block if any.
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if d.byteAvailable {
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// There is still one pending token that needs to be flushed
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d.tokens.AddLiteral(d.window[s.index-1])
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d.byteAvailable = false
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}
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if d.tokens.n > 0 {
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if d.err = d.writeBlock(&d.tokens, s.index, false); d.err != nil {
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return
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}
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d.tokens.Reset()
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}
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return
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}
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}
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if s.index < s.maxInsertIndex {
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// Update the hash
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s.hash = hash4(d.window[s.index:])
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ch := s.hashHead[s.hash&hashMask]
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s.chainHead = int(ch)
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s.hashPrev[s.index&windowMask] = ch
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s.hashHead[s.hash&hashMask] = uint32(s.index + s.hashOffset)
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}
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prevLength := s.length
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prevOffset := s.offset
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s.length = minMatchLength - 1
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s.offset = 0
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minIndex := s.index - windowSize
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if minIndex < 0 {
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minIndex = 0
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}
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if s.chainHead-s.hashOffset >= minIndex && lookahead > prevLength && prevLength < d.lazy {
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if newLength, newOffset, ok := d.findMatch(s.index, s.chainHead-s.hashOffset, lookahead); ok {
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s.length = newLength
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s.offset = newOffset
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}
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}
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if prevLength >= minMatchLength && s.length <= prevLength {
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// Check for better match at end...
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//
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// checkOff must be >=2 since we otherwise risk checking s.index
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// Offset of 2 seems to yield best results.
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const checkOff = 2
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prevIndex := s.index - 1
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if prevIndex+prevLength+checkOff < s.maxInsertIndex {
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end := lookahead
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if lookahead > maxMatchLength {
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end = maxMatchLength
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}
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end += prevIndex
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idx := prevIndex + prevLength - (4 - checkOff)
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h := hash4(d.window[idx:])
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ch2 := int(s.hashHead[h&hashMask]) - s.hashOffset - prevLength + (4 - checkOff)
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if ch2 > minIndex {
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length := matchLen(d.window[prevIndex:end], d.window[ch2:])
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// It seems like a pure length metric is best.
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if length > prevLength {
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prevLength = length
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prevOffset = prevIndex - ch2
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}
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}
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}
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// There was a match at the previous step, and the current match is
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// not better. Output the previous match.
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d.tokens.AddMatch(uint32(prevLength-3), uint32(prevOffset-minOffsetSize))
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|
|
// Insert in the hash table all strings up to the end of the match.
|
|
// index and index-1 are already inserted. If there is not enough
|
|
// lookahead, the last two strings are not inserted into the hash
|
|
// table.
|
|
newIndex := s.index + prevLength - 1
|
|
// Calculate missing hashes
|
|
end := newIndex
|
|
if end > s.maxInsertIndex {
|
|
end = s.maxInsertIndex
|
|
}
|
|
end += minMatchLength - 1
|
|
startindex := s.index + 1
|
|
if startindex > s.maxInsertIndex {
|
|
startindex = s.maxInsertIndex
|
|
}
|
|
tocheck := d.window[startindex:end]
|
|
dstSize := len(tocheck) - minMatchLength + 1
|
|
if dstSize > 0 {
|
|
dst := s.hashMatch[:dstSize]
|
|
bulkHash4(tocheck, dst)
|
|
var newH uint32
|
|
for i, val := range dst {
|
|
di := i + startindex
|
|
newH = val & hashMask
|
|
// Get previous value with the same hash.
|
|
// Our chain should point to the previous value.
|
|
s.hashPrev[di&windowMask] = s.hashHead[newH]
|
|
// Set the head of the hash chain to us.
|
|
s.hashHead[newH] = uint32(di + s.hashOffset)
|
|
}
|
|
s.hash = newH
|
|
}
|
|
|
|
s.index = newIndex
|
|
d.byteAvailable = false
|
|
s.length = minMatchLength - 1
|
|
if d.tokens.n == maxFlateBlockTokens {
|
|
// The block includes the current character
|
|
if d.err = d.writeBlock(&d.tokens, s.index, false); d.err != nil {
|
|
return
|
|
}
|
|
d.tokens.Reset()
|
|
}
|
|
s.ii = 0
|
|
} else {
|
|
// Reset, if we got a match this run.
|
|
if s.length >= minMatchLength {
|
|
s.ii = 0
|
|
}
|
|
// We have a byte waiting. Emit it.
|
|
if d.byteAvailable {
|
|
s.ii++
|
|
d.tokens.AddLiteral(d.window[s.index-1])
|
|
if d.tokens.n == maxFlateBlockTokens {
|
|
if d.err = d.writeBlock(&d.tokens, s.index, false); d.err != nil {
|
|
return
|
|
}
|
|
d.tokens.Reset()
|
|
}
|
|
s.index++
|
|
|
|
// If we have a long run of no matches, skip additional bytes
|
|
// Resets when s.ii overflows after 64KB.
|
|
if n := int(s.ii) - d.chain; n > 0 {
|
|
n = 1 + int(n>>6)
|
|
for j := 0; j < n; j++ {
|
|
if s.index >= d.windowEnd-1 {
|
|
break
|
|
}
|
|
d.tokens.AddLiteral(d.window[s.index-1])
|
|
if d.tokens.n == maxFlateBlockTokens {
|
|
if d.err = d.writeBlock(&d.tokens, s.index, false); d.err != nil {
|
|
return
|
|
}
|
|
d.tokens.Reset()
|
|
}
|
|
// Index...
|
|
if s.index < s.maxInsertIndex {
|
|
h := hash4(d.window[s.index:])
|
|
ch := s.hashHead[h]
|
|
s.chainHead = int(ch)
|
|
s.hashPrev[s.index&windowMask] = ch
|
|
s.hashHead[h] = uint32(s.index + s.hashOffset)
|
|
}
|
|
s.index++
|
|
}
|
|
// Flush last byte
|
|
d.tokens.AddLiteral(d.window[s.index-1])
|
|
d.byteAvailable = false
|
|
// s.length = minMatchLength - 1 // not needed, since s.ii is reset above, so it should never be > minMatchLength
|
|
if d.tokens.n == maxFlateBlockTokens {
|
|
if d.err = d.writeBlock(&d.tokens, s.index, false); d.err != nil {
|
|
return
|
|
}
|
|
d.tokens.Reset()
|
|
}
|
|
}
|
|
} else {
|
|
s.index++
|
|
d.byteAvailable = true
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
func (d *compressor) store() {
|
|
if d.windowEnd > 0 && (d.windowEnd == maxStoreBlockSize || d.sync) {
|
|
d.err = d.writeStoredBlock(d.window[:d.windowEnd])
|
|
d.windowEnd = 0
|
|
}
|
|
}
|
|
|
|
// fillWindow will fill the buffer with data for huffman-only compression.
|
|
// The number of bytes copied is returned.
|
|
func (d *compressor) fillBlock(b []byte) int {
|
|
n := copy(d.window[d.windowEnd:], b)
|
|
d.windowEnd += n
|
|
return n
|
|
}
|
|
|
|
// storeHuff will compress and store the currently added data,
|
|
// if enough has been accumulated or we at the end of the stream.
|
|
// Any error that occurred will be in d.err
|
|
func (d *compressor) storeHuff() {
|
|
if d.windowEnd < len(d.window) && !d.sync || d.windowEnd == 0 {
|
|
return
|
|
}
|
|
d.w.writeBlockHuff(false, d.window[:d.windowEnd], d.sync)
|
|
d.err = d.w.err
|
|
d.windowEnd = 0
|
|
}
|
|
|
|
// storeFast will compress and store the currently added data,
|
|
// if enough has been accumulated or we at the end of the stream.
|
|
// Any error that occurred will be in d.err
|
|
func (d *compressor) storeFast() {
|
|
// We only compress if we have maxStoreBlockSize.
|
|
if d.windowEnd < len(d.window) {
|
|
if !d.sync {
|
|
return
|
|
}
|
|
// Handle extremely small sizes.
|
|
if d.windowEnd < 128 {
|
|
if d.windowEnd == 0 {
|
|
return
|
|
}
|
|
if d.windowEnd <= 32 {
|
|
d.err = d.writeStoredBlock(d.window[:d.windowEnd])
|
|
} else {
|
|
d.w.writeBlockHuff(false, d.window[:d.windowEnd], true)
|
|
d.err = d.w.err
|
|
}
|
|
d.tokens.Reset()
|
|
d.windowEnd = 0
|
|
d.fast.Reset()
|
|
return
|
|
}
|
|
}
|
|
|
|
d.fast.Encode(&d.tokens, d.window[:d.windowEnd])
|
|
// If we made zero matches, store the block as is.
|
|
if d.tokens.n == 0 {
|
|
d.err = d.writeStoredBlock(d.window[:d.windowEnd])
|
|
// If we removed less than 1/16th, huffman compress the block.
|
|
} else if int(d.tokens.n) > d.windowEnd-(d.windowEnd>>4) {
|
|
d.w.writeBlockHuff(false, d.window[:d.windowEnd], d.sync)
|
|
d.err = d.w.err
|
|
} else {
|
|
d.w.writeBlockDynamic(&d.tokens, false, d.window[:d.windowEnd], d.sync)
|
|
d.err = d.w.err
|
|
}
|
|
d.tokens.Reset()
|
|
d.windowEnd = 0
|
|
}
|
|
|
|
// write will add input byte to the stream.
|
|
// Unless an error occurs all bytes will be consumed.
|
|
func (d *compressor) write(b []byte) (n int, err error) {
|
|
if d.err != nil {
|
|
return 0, d.err
|
|
}
|
|
n = len(b)
|
|
for len(b) > 0 {
|
|
if d.windowEnd == len(d.window) || d.sync {
|
|
d.step(d)
|
|
}
|
|
b = b[d.fill(d, b):]
|
|
if d.err != nil {
|
|
return 0, d.err
|
|
}
|
|
}
|
|
return n, d.err
|
|
}
|
|
|
|
func (d *compressor) syncFlush() error {
|
|
d.sync = true
|
|
if d.err != nil {
|
|
return d.err
|
|
}
|
|
d.step(d)
|
|
if d.err == nil {
|
|
d.w.writeStoredHeader(0, false)
|
|
d.w.flush()
|
|
d.err = d.w.err
|
|
}
|
|
d.sync = false
|
|
return d.err
|
|
}
|
|
|
|
func (d *compressor) init(w io.Writer, level int) (err error) {
|
|
d.w = newHuffmanBitWriter(w)
|
|
|
|
switch {
|
|
case level == NoCompression:
|
|
d.window = make([]byte, maxStoreBlockSize)
|
|
d.fill = (*compressor).fillBlock
|
|
d.step = (*compressor).store
|
|
case level == ConstantCompression:
|
|
d.w.logNewTablePenalty = 10
|
|
d.window = make([]byte, 32<<10)
|
|
d.fill = (*compressor).fillBlock
|
|
d.step = (*compressor).storeHuff
|
|
case level == DefaultCompression:
|
|
level = 5
|
|
fallthrough
|
|
case level >= 1 && level <= 6:
|
|
d.w.logNewTablePenalty = 7
|
|
d.fast = newFastEnc(level)
|
|
d.window = make([]byte, maxStoreBlockSize)
|
|
d.fill = (*compressor).fillBlock
|
|
d.step = (*compressor).storeFast
|
|
case 7 <= level && level <= 9:
|
|
d.w.logNewTablePenalty = 8
|
|
d.state = &advancedState{}
|
|
d.compressionLevel = levels[level]
|
|
d.initDeflate()
|
|
d.fill = (*compressor).fillDeflate
|
|
d.step = (*compressor).deflateLazy
|
|
default:
|
|
return fmt.Errorf("flate: invalid compression level %d: want value in range [-2, 9]", level)
|
|
}
|
|
d.level = level
|
|
return nil
|
|
}
|
|
|
|
// reset the state of the compressor.
|
|
func (d *compressor) reset(w io.Writer) {
|
|
d.w.reset(w)
|
|
d.sync = false
|
|
d.err = nil
|
|
// We only need to reset a few things for Snappy.
|
|
if d.fast != nil {
|
|
d.fast.Reset()
|
|
d.windowEnd = 0
|
|
d.tokens.Reset()
|
|
return
|
|
}
|
|
switch d.compressionLevel.chain {
|
|
case 0:
|
|
// level was NoCompression or ConstantCompresssion.
|
|
d.windowEnd = 0
|
|
default:
|
|
s := d.state
|
|
s.chainHead = -1
|
|
for i := range s.hashHead {
|
|
s.hashHead[i] = 0
|
|
}
|
|
for i := range s.hashPrev {
|
|
s.hashPrev[i] = 0
|
|
}
|
|
s.hashOffset = 1
|
|
s.index, d.windowEnd = 0, 0
|
|
d.blockStart, d.byteAvailable = 0, false
|
|
d.tokens.Reset()
|
|
s.length = minMatchLength - 1
|
|
s.offset = 0
|
|
s.hash = 0
|
|
s.ii = 0
|
|
s.maxInsertIndex = 0
|
|
}
|
|
}
|
|
|
|
func (d *compressor) close() error {
|
|
if d.err != nil {
|
|
return d.err
|
|
}
|
|
d.sync = true
|
|
d.step(d)
|
|
if d.err != nil {
|
|
return d.err
|
|
}
|
|
if d.w.writeStoredHeader(0, true); d.w.err != nil {
|
|
return d.w.err
|
|
}
|
|
d.w.flush()
|
|
d.w.reset(nil)
|
|
return d.w.err
|
|
}
|
|
|
|
// NewWriter returns a new Writer compressing data at the given level.
|
|
// Following zlib, levels range from 1 (BestSpeed) to 9 (BestCompression);
|
|
// higher levels typically run slower but compress more.
|
|
// Level 0 (NoCompression) does not attempt any compression; it only adds the
|
|
// necessary DEFLATE framing.
|
|
// Level -1 (DefaultCompression) uses the default compression level.
|
|
// Level -2 (ConstantCompression) will use Huffman compression only, giving
|
|
// a very fast compression for all types of input, but sacrificing considerable
|
|
// compression efficiency.
|
|
//
|
|
// If level is in the range [-2, 9] then the error returned will be nil.
|
|
// Otherwise the error returned will be non-nil.
|
|
func NewWriter(w io.Writer, level int) (*Writer, error) {
|
|
var dw Writer
|
|
if err := dw.d.init(w, level); err != nil {
|
|
return nil, err
|
|
}
|
|
return &dw, nil
|
|
}
|
|
|
|
// NewWriterDict is like NewWriter but initializes the new
|
|
// Writer with a preset dictionary. The returned Writer behaves
|
|
// as if the dictionary had been written to it without producing
|
|
// any compressed output. The compressed data written to w
|
|
// can only be decompressed by a Reader initialized with the
|
|
// same dictionary.
|
|
func NewWriterDict(w io.Writer, level int, dict []byte) (*Writer, error) {
|
|
zw, err := NewWriter(w, level)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
zw.d.fillWindow(dict)
|
|
zw.dict = append(zw.dict, dict...) // duplicate dictionary for Reset method.
|
|
return zw, err
|
|
}
|
|
|
|
// A Writer takes data written to it and writes the compressed
|
|
// form of that data to an underlying writer (see NewWriter).
|
|
type Writer struct {
|
|
d compressor
|
|
dict []byte
|
|
}
|
|
|
|
// Write writes data to w, which will eventually write the
|
|
// compressed form of data to its underlying writer.
|
|
func (w *Writer) Write(data []byte) (n int, err error) {
|
|
return w.d.write(data)
|
|
}
|
|
|
|
// Flush flushes any pending data to the underlying writer.
|
|
// It is useful mainly in compressed network protocols, to ensure that
|
|
// a remote reader has enough data to reconstruct a packet.
|
|
// Flush does not return until the data has been written.
|
|
// Calling Flush when there is no pending data still causes the Writer
|
|
// to emit a sync marker of at least 4 bytes.
|
|
// If the underlying writer returns an error, Flush returns that error.
|
|
//
|
|
// In the terminology of the zlib library, Flush is equivalent to Z_SYNC_FLUSH.
|
|
func (w *Writer) Flush() error {
|
|
// For more about flushing:
|
|
// http://www.bolet.org/~pornin/deflate-flush.html
|
|
return w.d.syncFlush()
|
|
}
|
|
|
|
// Close flushes and closes the writer.
|
|
func (w *Writer) Close() error {
|
|
return w.d.close()
|
|
}
|
|
|
|
// Reset discards the writer's state and makes it equivalent to
|
|
// the result of NewWriter or NewWriterDict called with dst
|
|
// and w's level and dictionary.
|
|
func (w *Writer) Reset(dst io.Writer) {
|
|
if len(w.dict) > 0 {
|
|
// w was created with NewWriterDict
|
|
w.d.reset(dst)
|
|
if dst != nil {
|
|
w.d.fillWindow(w.dict)
|
|
}
|
|
} else {
|
|
// w was created with NewWriter
|
|
w.d.reset(dst)
|
|
}
|
|
}
|
|
|
|
// ResetDict discards the writer's state and makes it equivalent to
|
|
// the result of NewWriter or NewWriterDict called with dst
|
|
// and w's level, but sets a specific dictionary.
|
|
func (w *Writer) ResetDict(dst io.Writer, dict []byte) {
|
|
w.dict = dict
|
|
w.d.reset(dst)
|
|
w.d.fillWindow(w.dict)
|
|
}
|