mirror of
https://github.com/golang/go
synced 2024-11-21 20:14:52 -07:00
compress/flate: do not use background goroutines
Programs expect that Read and Write are synchronous. The background goroutines make the implementation a little easier, but they introduce asynchrony that trips up calling code. Remove them. R=golang-dev, krasin CC=golang-dev https://golang.org/cl/4548079
This commit is contained in:
Russ Cox
parent
422abf3b8e
commit
07acc02a29
@ -11,16 +11,18 @@ import (
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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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fastCompression = 3
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BestCompression = 9
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DefaultCompression = -1
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logMaxOffsetSize = 15 // Standard DEFLATE
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wideLogMaxOffsetSize = 22 // Wide DEFLATE
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minMatchLength = 3 // 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 sence
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NoCompression = 0
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BestSpeed = 1
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fastCompression = 3
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BestCompression = 9
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DefaultCompression = -1
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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 = 3 // 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 sence
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// The maximum number of tokens we put into a single flat block, just too
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// stop things from getting too large.
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@ -32,22 +34,6 @@ const (
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hashShift = (hashBits + minMatchLength - 1) / minMatchLength
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)
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type syncPipeReader struct {
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*io.PipeReader
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closeChan chan bool
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}
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func (sr *syncPipeReader) CloseWithError(err os.Error) os.Error {
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retErr := sr.PipeReader.CloseWithError(err)
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sr.closeChan <- true // finish writer close
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return retErr
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}
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type syncPipeWriter struct {
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*io.PipeWriter
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closeChan chan bool
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}
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type compressionLevel struct {
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good, lazy, nice, chain, fastSkipHashing int
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}
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@ -68,105 +54,73 @@ var levels = []compressionLevel{
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{32, 258, 258, 4096, math.MaxInt32},
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}
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func (sw *syncPipeWriter) Close() os.Error {
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err := sw.PipeWriter.Close()
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<-sw.closeChan // wait for reader close
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return err
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}
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func syncPipe() (*syncPipeReader, *syncPipeWriter) {
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r, w := io.Pipe()
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sr := &syncPipeReader{r, make(chan bool, 1)}
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sw := &syncPipeWriter{w, sr.closeChan}
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return sr, sw
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}
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type compressor struct {
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level int
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logWindowSize uint
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w *huffmanBitWriter
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r io.Reader
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// (1 << logWindowSize) - 1.
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windowMask int
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compressionLevel
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eof bool // has eof been reached on input?
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sync bool // writer wants to flush
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syncChan chan os.Error
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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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sync bool // requesting flush
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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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hashHead []int
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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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hashPrev []int
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chainHead int
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hashHead []int
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hashPrev []int
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// If we find a match of length >= niceMatch, then we don't bother searching
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// any further.
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niceMatch int
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// input window: unprocessed data is window[index:windowEnd]
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index int
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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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byteAvailable bool // if true, still need to process window[index-1].
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// If we find a match of length >= goodMatch, we only do a half-hearted
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// effort at doing lazy matching starting at the next character
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goodMatch int
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// queued output tokens: tokens[:ti]
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tokens []token
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ti int
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// The maximum number of chains we look at when finding a match
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maxChainLength int
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// The sliding window we use for matching
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window []byte
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// The index just past the last valid character
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windowEnd int
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// index in "window" at which current block starts
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blockStart int
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// deflate state
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length int
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offset int
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hash int
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maxInsertIndex int
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err os.Error
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}
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func (d *compressor) flush() os.Error {
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d.w.flush()
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return d.w.err
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}
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func (d *compressor) fillWindow(index int) (int, os.Error) {
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if d.sync {
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return index, nil
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}
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wSize := d.windowMask + 1
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if index >= wSize+wSize-(minMatchLength+maxMatchLength) {
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// shift the window by wSize
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copy(d.window, d.window[wSize:2*wSize])
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index -= wSize
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d.windowEnd -= wSize
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if d.blockStart >= wSize {
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d.blockStart -= wSize
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func (d *compressor) fillDeflate(b []byte) int {
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if d.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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d.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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for i, h := range d.hashHead {
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v := h - wSize
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v := h - windowSize
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if v < -1 {
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v = -1
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}
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d.hashHead[i] = v
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}
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for i, h := range d.hashPrev {
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v := -h - wSize
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v := -h - windowSize
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if v < -1 {
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v = -1
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}
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d.hashPrev[i] = v
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}
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}
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count, err := d.r.Read(d.window[d.windowEnd:])
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d.windowEnd += count
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if count == 0 && err == nil {
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d.sync = true
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}
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if err == os.EOF {
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d.eof = true
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err = nil
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}
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return index, err
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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(tokens []token, index int, eof bool) os.Error {
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@ -194,21 +148,21 @@ func (d *compressor) findMatch(pos int, prevHead int, prevLength int, lookahead
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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.niceMatch < nice {
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nice = d.niceMatch
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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.maxChainLength
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tries := d.chain
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length = prevLength
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if length >= d.goodMatch {
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if length >= d.good {
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tries >>= 2
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}
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w0 := win[pos]
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w1 := win[pos+1]
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wEnd := win[pos+length]
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minIndex := pos - (d.windowMask + 1)
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minIndex := pos - windowSize
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for i := prevHead; tries > 0; tries-- {
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if w0 == win[i] && w1 == win[i+1] && wEnd == win[i+length] {
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@ -233,7 +187,7 @@ func (d *compressor) findMatch(pos int, prevHead int, prevLength int, lookahead
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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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if i = d.hashPrev[i&d.windowMask]; i < minIndex || i < 0 {
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if i = d.hashPrev[i&windowMask]; i < minIndex || i < 0 {
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break
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}
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}
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@ -248,234 +202,224 @@ func (d *compressor) writeStoredBlock(buf []byte) os.Error {
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return d.w.err
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}
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func (d *compressor) storedDeflate() os.Error {
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buf := make([]byte, maxStoreBlockSize)
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for {
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n, err := d.r.Read(buf)
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if n == 0 && err == nil {
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d.sync = true
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}
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if n > 0 || d.sync {
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if err := d.writeStoredBlock(buf[0:n]); err != nil {
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return err
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}
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if d.sync {
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d.syncChan <- nil
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d.sync = false
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}
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}
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if err != nil {
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if err == os.EOF {
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break
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}
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return err
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}
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}
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return nil
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func (d *compressor) initDeflate() {
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d.hashHead = make([]int, hashSize)
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d.hashPrev = make([]int, windowSize)
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d.window = make([]byte, 2*windowSize)
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fillInts(d.hashHead, -1)
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d.tokens = make([]token, maxFlateBlockTokens, maxFlateBlockTokens+1)
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d.length = minMatchLength - 1
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d.offset = 0
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d.byteAvailable = false
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d.index = 0
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d.ti = 0
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d.hash = 0
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d.chainHead = -1
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}
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func (d *compressor) doDeflate() (err os.Error) {
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// init
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d.windowMask = 1<<d.logWindowSize - 1
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d.hashHead = make([]int, hashSize)
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d.hashPrev = make([]int, 1<<d.logWindowSize)
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d.window = make([]byte, 2<<d.logWindowSize)
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fillInts(d.hashHead, -1)
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tokens := make([]token, maxFlateBlockTokens, maxFlateBlockTokens+1)
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l := levels[d.level]
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d.goodMatch = l.good
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d.niceMatch = l.nice
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d.maxChainLength = l.chain
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lazyMatch := l.lazy
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length := minMatchLength - 1
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offset := 0
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byteAvailable := false
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isFastDeflate := l.fastSkipHashing != 0
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index := 0
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// run
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if index, err = d.fillWindow(index); err != nil {
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func (d *compressor) deflate() {
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if d.windowEnd-d.index < minMatchLength+maxMatchLength && !d.sync {
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return
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}
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maxOffset := d.windowMask + 1 // (1 << logWindowSize);
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// only need to change when you refill the window
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windowEnd := d.windowEnd
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maxInsertIndex := windowEnd - (minMatchLength - 1)
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ti := 0
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hash := int(0)
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if index < maxInsertIndex {
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hash = int(d.window[index])<<hashShift + int(d.window[index+1])
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d.maxInsertIndex = d.windowEnd - (minMatchLength - 1)
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if d.index < d.maxInsertIndex {
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d.hash = int(d.window[d.index])<<hashShift + int(d.window[d.index+1])
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}
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chainHead := -1
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Loop:
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for {
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if index > windowEnd {
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if d.index > d.windowEnd {
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panic("index > windowEnd")
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}
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lookahead := windowEnd - index
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lookahead := d.windowEnd - d.index
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if lookahead < minMatchLength+maxMatchLength {
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if index, err = d.fillWindow(index); err != nil {
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return
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if !d.sync {
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break Loop
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}
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windowEnd = d.windowEnd
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if index > windowEnd {
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if d.index > d.windowEnd {
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panic("index > windowEnd")
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}
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maxInsertIndex = windowEnd - (minMatchLength - 1)
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lookahead = windowEnd - index
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if lookahead == 0 {
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// Flush current output block if any.
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if byteAvailable {
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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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tokens[ti] = literalToken(uint32(d.window[index-1]) & 0xFF)
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ti++
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byteAvailable = false
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d.tokens[d.ti] = literalToken(uint32(d.window[d.index-1]))
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d.ti++
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d.byteAvailable = false
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}
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if ti > 0 {
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if err = d.writeBlock(tokens[0:ti], index, false); err != nil {
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if d.ti > 0 {
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if d.err = d.writeBlock(d.tokens[0:d.ti], d.index, false); d.err != nil {
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return
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}
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ti = 0
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}
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if d.sync {
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d.w.writeStoredHeader(0, false)
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d.w.flush()
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d.syncChan <- d.w.err
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d.sync = false
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}
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// If this was only a sync (not at EOF) keep going.
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if !d.eof {
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continue
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d.ti = 0
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}
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break Loop
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}
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}
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if index < maxInsertIndex {
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if d.index < d.maxInsertIndex {
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// Update the hash
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hash = (hash<<hashShift + int(d.window[index+2])) & hashMask
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chainHead = d.hashHead[hash]
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d.hashPrev[index&d.windowMask] = chainHead
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d.hashHead[hash] = index
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d.hash = (d.hash<<hashShift + int(d.window[d.index+2])) & hashMask
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d.chainHead = d.hashHead[d.hash]
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d.hashPrev[d.index&windowMask] = d.chainHead
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d.hashHead[d.hash] = d.index
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}
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prevLength := length
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prevOffset := offset
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length = minMatchLength - 1
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offset = 0
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minIndex := index - maxOffset
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prevLength := d.length
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prevOffset := d.offset
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d.length = minMatchLength - 1
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d.offset = 0
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minIndex := d.index - windowSize
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if minIndex < 0 {
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minIndex = 0
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}
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if chainHead >= minIndex &&
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(isFastDeflate && lookahead > minMatchLength-1 ||
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!isFastDeflate && lookahead > prevLength && prevLength < lazyMatch) {
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if newLength, newOffset, ok := d.findMatch(index, chainHead, minMatchLength-1, lookahead); ok {
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length = newLength
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offset = newOffset
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if d.chainHead >= minIndex &&
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(d.fastSkipHashing != 0 && lookahead > minMatchLength-1 ||
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d.fastSkipHashing == 0 && lookahead > prevLength && prevLength < d.lazy) {
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if newLength, newOffset, ok := d.findMatch(d.index, d.chainHead, minMatchLength-1, lookahead); ok {
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d.length = newLength
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d.offset = newOffset
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}
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}
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if isFastDeflate && length >= minMatchLength ||
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!isFastDeflate && prevLength >= minMatchLength && length <= prevLength {
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if d.fastSkipHashing != 0 && d.length >= minMatchLength ||
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d.fastSkipHashing == 0 && prevLength >= minMatchLength && d.length <= prevLength {
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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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if isFastDeflate {
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tokens[ti] = matchToken(uint32(length-minMatchLength), uint32(offset-minOffsetSize))
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if d.fastSkipHashing != 0 {
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d.tokens[d.ti] = matchToken(uint32(d.length-minMatchLength), uint32(d.offset-minOffsetSize))
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} else {
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tokens[ti] = matchToken(uint32(prevLength-minMatchLength), uint32(prevOffset-minOffsetSize))
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d.tokens[d.ti] = matchToken(uint32(prevLength-minMatchLength), uint32(prevOffset-minOffsetSize))
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}
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ti++
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d.ti++
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// Insert in the hash table all strings up to the end of the match.
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// index and index-1 are already inserted. If there is not enough
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// lookahead, the last two strings are not inserted into the hash
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// table.
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if length <= l.fastSkipHashing {
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if d.length <= d.fastSkipHashing {
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var newIndex int
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if isFastDeflate {
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newIndex = index + length
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if d.fastSkipHashing != 0 {
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newIndex = d.index + d.length
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} else {
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newIndex = prevLength - 1
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}
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for index++; index < newIndex; index++ {
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if index < maxInsertIndex {
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hash = (hash<<hashShift + int(d.window[index+2])) & hashMask
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for d.index++; d.index < newIndex; d.index++ {
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if d.index < d.maxInsertIndex {
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d.hash = (d.hash<<hashShift + int(d.window[d.index+2])) & 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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d.hashPrev[index&d.windowMask] = d.hashHead[hash]
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d.hashPrev[d.index&windowMask] = d.hashHead[d.hash]
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// Set the head of the hash chain to us.
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d.hashHead[hash] = index
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d.hashHead[d.hash] = d.index
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}
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}
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if !isFastDeflate {
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byteAvailable = false
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length = minMatchLength - 1
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if d.fastSkipHashing == 0 {
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d.byteAvailable = false
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d.length = minMatchLength - 1
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}
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} else {
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// For matches this long, we don't bother inserting each individual
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// item into the table.
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index += length
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hash = (int(d.window[index])<<hashShift + int(d.window[index+1]))
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d.index += d.length
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d.hash = (int(d.window[d.index])<<hashShift + int(d.window[d.index+1]))
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}
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if ti == maxFlateBlockTokens {
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if d.ti == maxFlateBlockTokens {
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// The block includes the current character
|
||||
if err = d.writeBlock(tokens, index, false); err != nil {
|
||||
if d.err = d.writeBlock(d.tokens, d.index, false); d.err != nil {
|
||||
return
|
||||
}
|
||||
ti = 0
|
||||
d.ti = 0
|
||||
}
|
||||
} else {
|
||||
if isFastDeflate || byteAvailable {
|
||||
i := index - 1
|
||||
if isFastDeflate {
|
||||
i = index
|
||||
if d.fastSkipHashing != 0 || d.byteAvailable {
|
||||
i := d.index - 1
|
||||
if d.fastSkipHashing != 0 {
|
||||
i = d.index
|
||||
}
|
||||
tokens[ti] = literalToken(uint32(d.window[i]) & 0xFF)
|
||||
ti++
|
||||
if ti == maxFlateBlockTokens {
|
||||
if err = d.writeBlock(tokens, i+1, false); err != nil {
|
||||
d.tokens[d.ti] = literalToken(uint32(d.window[i]))
|
||||
d.ti++
|
||||
if d.ti == maxFlateBlockTokens {
|
||||
if d.err = d.writeBlock(d.tokens, i+1, false); d.err != nil {
|
||||
return
|
||||
}
|
||||
ti = 0
|
||||
d.ti = 0
|
||||
}
|
||||
}
|
||||
index++
|
||||
if !isFastDeflate {
|
||||
byteAvailable = true
|
||||
d.index++
|
||||
if d.fastSkipHashing == 0 {
|
||||
d.byteAvailable = true
|
||||
}
|
||||
}
|
||||
}
|
||||
return
|
||||
}
|
||||
|
||||
func (d *compressor) compress(r io.Reader, w io.Writer, level int, logWindowSize uint) (err os.Error) {
|
||||
d.r = r
|
||||
func (d *compressor) fillStore(b []byte) int {
|
||||
n := copy(d.window[d.windowEnd:], b)
|
||||
d.windowEnd += n
|
||||
return n
|
||||
}
|
||||
|
||||
func (d *compressor) store() {
|
||||
if d.windowEnd > 0 {
|
||||
d.err = d.writeStoredBlock(d.window[:d.windowEnd])
|
||||
}
|
||||
d.windowEnd = 0
|
||||
}
|
||||
|
||||
func (d *compressor) write(b []byte) (n int, err os.Error) {
|
||||
n = len(b)
|
||||
b = b[d.fill(d, b):]
|
||||
for len(b) > 0 {
|
||||
d.step(d)
|
||||
b = b[d.fill(d, b):]
|
||||
}
|
||||
return n, d.err
|
||||
}
|
||||
|
||||
func (d *compressor) syncFlush() os.Error {
|
||||
d.sync = true
|
||||
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 os.Error) {
|
||||
d.w = newHuffmanBitWriter(w)
|
||||
d.level = level
|
||||
d.logWindowSize = logWindowSize
|
||||
|
||||
switch {
|
||||
case level == NoCompression:
|
||||
err = d.storedDeflate()
|
||||
d.window = make([]byte, maxStoreBlockSize)
|
||||
d.fill = (*compressor).fillStore
|
||||
d.step = (*compressor).store
|
||||
case level == DefaultCompression:
|
||||
d.level = 6
|
||||
level = 6
|
||||
fallthrough
|
||||
case 1 <= level && level <= 9:
|
||||
err = d.doDeflate()
|
||||
d.compressionLevel = levels[level]
|
||||
d.initDeflate()
|
||||
d.fill = (*compressor).fillDeflate
|
||||
d.step = (*compressor).deflate
|
||||
default:
|
||||
return WrongValueError{"level", 0, 9, int32(level)}
|
||||
}
|
||||
return nil
|
||||
}
|
||||
|
||||
if d.sync {
|
||||
d.syncChan <- err
|
||||
d.sync = false
|
||||
}
|
||||
if err != nil {
|
||||
return err
|
||||
func (d *compressor) close() os.Error {
|
||||
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
|
||||
}
|
||||
return d.flush()
|
||||
d.w.flush()
|
||||
return d.w.err
|
||||
}
|
||||
|
||||
// NewWriter returns a new Writer compressing
|
||||
@ -486,14 +430,9 @@ func (d *compressor) compress(r io.Reader, w io.Writer, level int, logWindowSize
|
||||
// compression; it only adds the necessary DEFLATE framing.
|
||||
func NewWriter(w io.Writer, level int) *Writer {
|
||||
const logWindowSize = logMaxOffsetSize
|
||||
var d compressor
|
||||
d.syncChan = make(chan os.Error, 1)
|
||||
pr, pw := syncPipe()
|
||||
go func() {
|
||||
err := d.compress(pr, w, level, logWindowSize)
|
||||
pr.CloseWithError(err)
|
||||
}()
|
||||
return &Writer{pw, &d}
|
||||
var dw Writer
|
||||
dw.d.init(w, level)
|
||||
return &dw
|
||||
}
|
||||
|
||||
// NewWriterDict is like NewWriter but initializes the new
|
||||
@ -526,18 +465,13 @@ func (w *dictWriter) Write(b []byte) (n int, err os.Error) {
|
||||
// A Writer takes data written to it and writes the compressed
|
||||
// form of that data to an underlying writer (see NewWriter).
|
||||
type Writer struct {
|
||||
w *syncPipeWriter
|
||||
d *compressor
|
||||
d compressor
|
||||
}
|
||||
|
||||
// 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 os.Error) {
|
||||
if len(data) == 0 {
|
||||
// no point, and nil interferes with sync
|
||||
return
|
||||
}
|
||||
return w.w.Write(data)
|
||||
return w.d.write(data)
|
||||
}
|
||||
|
||||
// Flush flushes any pending compressed data to the underlying writer.
|
||||
@ -550,18 +484,10 @@ func (w *Writer) Write(data []byte) (n int, err os.Error) {
|
||||
func (w *Writer) Flush() os.Error {
|
||||
// For more about flushing:
|
||||
// http://www.bolet.org/~pornin/deflate-flush.html
|
||||
if w.d.sync {
|
||||
panic("compress/flate: double Flush")
|
||||
}
|
||||
_, err := w.w.Write(nil)
|
||||
err1 := <-w.d.syncChan
|
||||
if err == nil {
|
||||
err = err1
|
||||
}
|
||||
return err
|
||||
return w.d.syncFlush()
|
||||
}
|
||||
|
||||
// Close flushes and closes the writer.
|
||||
func (w *Writer) Close() os.Error {
|
||||
return w.w.Close()
|
||||
return w.d.close()
|
||||
}
|
||||
|
||||
@ -57,7 +57,7 @@ var deflateInflateTests = []*deflateInflateTest{
|
||||
&deflateInflateTest{[]byte{0x11, 0x12}},
|
||||
&deflateInflateTest{[]byte{0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11}},
|
||||
&deflateInflateTest{[]byte{0x11, 0x10, 0x13, 0x41, 0x21, 0x21, 0x41, 0x13, 0x87, 0x78, 0x13}},
|
||||
&deflateInflateTest{getLargeDataChunk()},
|
||||
&deflateInflateTest{largeDataChunk()},
|
||||
}
|
||||
|
||||
var reverseBitsTests = []*reverseBitsTest{
|
||||
@ -71,23 +71,22 @@ var reverseBitsTests = []*reverseBitsTest{
|
||||
&reverseBitsTest{29, 5, 23},
|
||||
}
|
||||
|
||||
func getLargeDataChunk() []byte {
|
||||
func largeDataChunk() []byte {
|
||||
result := make([]byte, 100000)
|
||||
for i := range result {
|
||||
result[i] = byte(int64(i) * int64(i) & 0xFF)
|
||||
result[i] = byte(i * i & 0xFF)
|
||||
}
|
||||
return result
|
||||
}
|
||||
|
||||
func TestDeflate(t *testing.T) {
|
||||
for _, h := range deflateTests {
|
||||
buffer := bytes.NewBuffer(nil)
|
||||
w := NewWriter(buffer, h.level)
|
||||
var buf bytes.Buffer
|
||||
w := NewWriter(&buf, h.level)
|
||||
w.Write(h.in)
|
||||
w.Close()
|
||||
if bytes.Compare(buffer.Bytes(), h.out) != 0 {
|
||||
t.Errorf("buffer is wrong; level = %v, buffer.Bytes() = %v, expected output = %v",
|
||||
h.level, buffer.Bytes(), h.out)
|
||||
if !bytes.Equal(buf.Bytes(), h.out) {
|
||||
t.Errorf("Deflate(%d, %x) = %x, want %x", h.level, h.in, buf.Bytes(), h.out)
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
@ -195,9 +195,8 @@ type Reader interface {
|
||||
|
||||
// Decompress state.
|
||||
type decompressor struct {
|
||||
// Input/output sources.
|
||||
// Input source.
|
||||
r Reader
|
||||
w io.Writer
|
||||
roffset int64
|
||||
woffset int64
|
||||
|
||||
@ -220,38 +219,79 @@ type decompressor struct {
|
||||
|
||||
// Temporary buffer (avoids repeated allocation).
|
||||
buf [4]byte
|
||||
|
||||
// Next step in the decompression,
|
||||
// and decompression state.
|
||||
step func(*decompressor)
|
||||
final bool
|
||||
err os.Error
|
||||
toRead []byte
|
||||
hl, hd *huffmanDecoder
|
||||
copyLen int
|
||||
copyDist int
|
||||
}
|
||||
|
||||
func (f *decompressor) inflate() (err os.Error) {
|
||||
final := false
|
||||
for err == nil && !final {
|
||||
for f.nb < 1+2 {
|
||||
if err = f.moreBits(); err != nil {
|
||||
return
|
||||
}
|
||||
func (f *decompressor) nextBlock() {
|
||||
if f.final {
|
||||
if f.hw != f.hp {
|
||||
f.flush((*decompressor).nextBlock)
|
||||
return
|
||||
}
|
||||
final = f.b&1 == 1
|
||||
f.b >>= 1
|
||||
typ := f.b & 3
|
||||
f.b >>= 2
|
||||
f.nb -= 1 + 2
|
||||
switch typ {
|
||||
case 0:
|
||||
err = f.dataBlock()
|
||||
case 1:
|
||||
// compressed, fixed Huffman tables
|
||||
err = f.decodeBlock(&fixedHuffmanDecoder, nil)
|
||||
case 2:
|
||||
// compressed, dynamic Huffman tables
|
||||
if err = f.readHuffman(); err == nil {
|
||||
err = f.decodeBlock(&f.h1, &f.h2)
|
||||
}
|
||||
default:
|
||||
// 3 is reserved.
|
||||
err = CorruptInputError(f.roffset)
|
||||
f.err = os.EOF
|
||||
return
|
||||
}
|
||||
for f.nb < 1+2 {
|
||||
if f.err = f.moreBits(); f.err != nil {
|
||||
return
|
||||
}
|
||||
}
|
||||
return
|
||||
f.final = f.b&1 == 1
|
||||
f.b >>= 1
|
||||
typ := f.b & 3
|
||||
f.b >>= 2
|
||||
f.nb -= 1 + 2
|
||||
switch typ {
|
||||
case 0:
|
||||
f.dataBlock()
|
||||
case 1:
|
||||
// compressed, fixed Huffman tables
|
||||
f.hl = &fixedHuffmanDecoder
|
||||
f.hd = nil
|
||||
f.huffmanBlock()
|
||||
case 2:
|
||||
// compressed, dynamic Huffman tables
|
||||
if f.err = f.readHuffman(); f.err != nil {
|
||||
break
|
||||
}
|
||||
f.hl = &f.h1
|
||||
f.hd = &f.h2
|
||||
f.huffmanBlock()
|
||||
default:
|
||||
// 3 is reserved.
|
||||
f.err = CorruptInputError(f.roffset)
|
||||
}
|
||||
}
|
||||
|
||||
func (f *decompressor) Read(b []byte) (int, os.Error) {
|
||||
for {
|
||||
if len(f.toRead) > 0 {
|
||||
n := copy(b, f.toRead)
|
||||
f.toRead = f.toRead[n:]
|
||||
return n, nil
|
||||
}
|
||||
if f.err != nil {
|
||||
return 0, f.err
|
||||
}
|
||||
f.step(f)
|
||||
}
|
||||
panic("unreachable")
|
||||
}
|
||||
|
||||
func (f *decompressor) Close() os.Error {
|
||||
if f.err == os.EOF {
|
||||
return nil
|
||||
}
|
||||
return f.err
|
||||
}
|
||||
|
||||
// RFC 1951 section 3.2.7.
|
||||
@ -356,11 +396,12 @@ func (f *decompressor) readHuffman() os.Error {
|
||||
// hl and hd are the Huffman states for the lit/length values
|
||||
// and the distance values, respectively. If hd == nil, using the
|
||||
// fixed distance encoding associated with fixed Huffman blocks.
|
||||
func (f *decompressor) decodeBlock(hl, hd *huffmanDecoder) os.Error {
|
||||
func (f *decompressor) huffmanBlock() {
|
||||
for {
|
||||
v, err := f.huffSym(hl)
|
||||
v, err := f.huffSym(f.hl)
|
||||
if err != nil {
|
||||
return err
|
||||
f.err = err
|
||||
return
|
||||
}
|
||||
var n uint // number of bits extra
|
||||
var length int
|
||||
@ -369,13 +410,15 @@ func (f *decompressor) decodeBlock(hl, hd *huffmanDecoder) os.Error {
|
||||
f.hist[f.hp] = byte(v)
|
||||
f.hp++
|
||||
if f.hp == len(f.hist) {
|
||||
if err = f.flush(); err != nil {
|
||||
return err
|
||||
}
|
||||
// After the flush, continue this loop.
|
||||
f.flush((*decompressor).huffmanBlock)
|
||||
return
|
||||
}
|
||||
continue
|
||||
case v == 256:
|
||||
return nil
|
||||
// Done with huffman block; read next block.
|
||||
f.step = (*decompressor).nextBlock
|
||||
return
|
||||
// otherwise, reference to older data
|
||||
case v < 265:
|
||||
length = v - (257 - 3)
|
||||
@ -402,7 +445,8 @@ func (f *decompressor) decodeBlock(hl, hd *huffmanDecoder) os.Error {
|
||||
if n > 0 {
|
||||
for f.nb < n {
|
||||
if err = f.moreBits(); err != nil {
|
||||
return err
|
||||
f.err = err
|
||||
return
|
||||
}
|
||||
}
|
||||
length += int(f.b & uint32(1<<n-1))
|
||||
@ -411,18 +455,20 @@ func (f *decompressor) decodeBlock(hl, hd *huffmanDecoder) os.Error {
|
||||
}
|
||||
|
||||
var dist int
|
||||
if hd == nil {
|
||||
if f.hd == nil {
|
||||
for f.nb < 5 {
|
||||
if err = f.moreBits(); err != nil {
|
||||
return err
|
||||
f.err = err
|
||||
return
|
||||
}
|
||||
}
|
||||
dist = int(reverseByte[(f.b&0x1F)<<3])
|
||||
f.b >>= 5
|
||||
f.nb -= 5
|
||||
} else {
|
||||
if dist, err = f.huffSym(hd); err != nil {
|
||||
return err
|
||||
if dist, err = f.huffSym(f.hd); err != nil {
|
||||
f.err = err
|
||||
return
|
||||
}
|
||||
}
|
||||
|
||||
@ -430,14 +476,16 @@ func (f *decompressor) decodeBlock(hl, hd *huffmanDecoder) os.Error {
|
||||
case dist < 4:
|
||||
dist++
|
||||
case dist >= 30:
|
||||
return CorruptInputError(f.roffset)
|
||||
f.err = CorruptInputError(f.roffset)
|
||||
return
|
||||
default:
|
||||
nb := uint(dist-2) >> 1
|
||||
// have 1 bit in bottom of dist, need nb more.
|
||||
extra := (dist & 1) << nb
|
||||
for f.nb < nb {
|
||||
if err = f.moreBits(); err != nil {
|
||||
return err
|
||||
f.err = err
|
||||
return
|
||||
}
|
||||
}
|
||||
extra |= int(f.b & uint32(1<<nb-1))
|
||||
@ -448,12 +496,14 @@ func (f *decompressor) decodeBlock(hl, hd *huffmanDecoder) os.Error {
|
||||
|
||||
// Copy history[-dist:-dist+length] into output.
|
||||
if dist > len(f.hist) {
|
||||
return InternalError("bad history distance")
|
||||
f.err = InternalError("bad history distance")
|
||||
return
|
||||
}
|
||||
|
||||
// No check on length; encoding can be prescient.
|
||||
if !f.hfull && dist > f.hp {
|
||||
return CorruptInputError(f.roffset)
|
||||
f.err = CorruptInputError(f.roffset)
|
||||
return
|
||||
}
|
||||
|
||||
p := f.hp - dist
|
||||
@ -465,9 +515,11 @@ func (f *decompressor) decodeBlock(hl, hd *huffmanDecoder) os.Error {
|
||||
f.hp++
|
||||
p++
|
||||
if f.hp == len(f.hist) {
|
||||
if err = f.flush(); err != nil {
|
||||
return err
|
||||
}
|
||||
// After flush continue copying out of history.
|
||||
f.copyLen = length - (i + 1)
|
||||
f.copyDist = dist
|
||||
f.flush((*decompressor).copyHuff)
|
||||
return
|
||||
}
|
||||
if p == len(f.hist) {
|
||||
p = 0
|
||||
@ -477,8 +529,33 @@ func (f *decompressor) decodeBlock(hl, hd *huffmanDecoder) os.Error {
|
||||
panic("unreached")
|
||||
}
|
||||
|
||||
func (f *decompressor) copyHuff() {
|
||||
length := f.copyLen
|
||||
dist := f.copyDist
|
||||
p := f.hp - dist
|
||||
if p < 0 {
|
||||
p += len(f.hist)
|
||||
}
|
||||
for i := 0; i < length; i++ {
|
||||
f.hist[f.hp] = f.hist[p]
|
||||
f.hp++
|
||||
p++
|
||||
if f.hp == len(f.hist) {
|
||||
f.copyLen = length - (i + 1)
|
||||
f.flush((*decompressor).copyHuff)
|
||||
return
|
||||
}
|
||||
if p == len(f.hist) {
|
||||
p = 0
|
||||
}
|
||||
}
|
||||
|
||||
// Continue processing Huffman block.
|
||||
f.huffmanBlock()
|
||||
}
|
||||
|
||||
// Copy a single uncompressed data block from input to output.
|
||||
func (f *decompressor) dataBlock() os.Error {
|
||||
func (f *decompressor) dataBlock() {
|
||||
// Uncompressed.
|
||||
// Discard current half-byte.
|
||||
f.nb = 0
|
||||
@ -488,21 +565,30 @@ func (f *decompressor) dataBlock() os.Error {
|
||||
nr, err := io.ReadFull(f.r, f.buf[0:4])
|
||||
f.roffset += int64(nr)
|
||||
if err != nil {
|
||||
return &ReadError{f.roffset, err}
|
||||
f.err = &ReadError{f.roffset, err}
|
||||
return
|
||||
}
|
||||
n := int(f.buf[0]) | int(f.buf[1])<<8
|
||||
nn := int(f.buf[2]) | int(f.buf[3])<<8
|
||||
if uint16(nn) != uint16(^n) {
|
||||
return CorruptInputError(f.roffset)
|
||||
f.err = CorruptInputError(f.roffset)
|
||||
return
|
||||
}
|
||||
|
||||
if n == 0 {
|
||||
// 0-length block means sync
|
||||
return f.flush()
|
||||
f.flush((*decompressor).nextBlock)
|
||||
return
|
||||
}
|
||||
|
||||
// Read len bytes into history,
|
||||
// writing as history fills.
|
||||
f.copyLen = n
|
||||
f.copyData()
|
||||
}
|
||||
|
||||
func (f *decompressor) copyData() {
|
||||
// Read f.dataLen bytes into history,
|
||||
// pausing for reads as history fills.
|
||||
n := f.copyLen
|
||||
for n > 0 {
|
||||
m := len(f.hist) - f.hp
|
||||
if m > n {
|
||||
@ -511,17 +597,18 @@ func (f *decompressor) dataBlock() os.Error {
|
||||
m, err := io.ReadFull(f.r, f.hist[f.hp:f.hp+m])
|
||||
f.roffset += int64(m)
|
||||
if err != nil {
|
||||
return &ReadError{f.roffset, err}
|
||||
f.err = &ReadError{f.roffset, err}
|
||||
return
|
||||
}
|
||||
n -= m
|
||||
f.hp += m
|
||||
if f.hp == len(f.hist) {
|
||||
if err = f.flush(); err != nil {
|
||||
return err
|
||||
}
|
||||
f.copyLen = n
|
||||
f.flush((*decompressor).copyData)
|
||||
return
|
||||
}
|
||||
}
|
||||
return nil
|
||||
f.step = (*decompressor).nextBlock
|
||||
}
|
||||
|
||||
func (f *decompressor) setDict(dict []byte) {
|
||||
@ -577,17 +664,8 @@ func (f *decompressor) huffSym(h *huffmanDecoder) (int, os.Error) {
|
||||
}
|
||||
|
||||
// Flush any buffered output to the underlying writer.
|
||||
func (f *decompressor) flush() os.Error {
|
||||
if f.hw == f.hp {
|
||||
return nil
|
||||
}
|
||||
n, err := f.w.Write(f.hist[f.hw:f.hp])
|
||||
if n != f.hp-f.hw && err == nil {
|
||||
err = io.ErrShortWrite
|
||||
}
|
||||
if err != nil {
|
||||
return &WriteError{f.woffset, err}
|
||||
}
|
||||
func (f *decompressor) flush(step func(*decompressor)) {
|
||||
f.toRead = f.hist[f.hw:f.hp]
|
||||
f.woffset += int64(f.hp - f.hw)
|
||||
f.hw = f.hp
|
||||
if f.hp == len(f.hist) {
|
||||
@ -595,7 +673,7 @@ func (f *decompressor) flush() os.Error {
|
||||
f.hw = 0
|
||||
f.hfull = true
|
||||
}
|
||||
return nil
|
||||
f.step = step
|
||||
}
|
||||
|
||||
func makeReader(r io.Reader) Reader {
|
||||
@ -605,30 +683,15 @@ func makeReader(r io.Reader) Reader {
|
||||
return bufio.NewReader(r)
|
||||
}
|
||||
|
||||
// decompress reads DEFLATE-compressed data from r and writes
|
||||
// the uncompressed data to w.
|
||||
func (f *decompressor) decompress(r io.Reader, w io.Writer) os.Error {
|
||||
f.r = makeReader(r)
|
||||
f.w = w
|
||||
f.woffset = 0
|
||||
if err := f.inflate(); err != nil {
|
||||
return err
|
||||
}
|
||||
if err := f.flush(); err != nil {
|
||||
return err
|
||||
}
|
||||
return nil
|
||||
}
|
||||
|
||||
// NewReader returns a new ReadCloser that can be used
|
||||
// to read the uncompressed version of r. It is the caller's
|
||||
// responsibility to call Close on the ReadCloser when
|
||||
// finished reading.
|
||||
func NewReader(r io.Reader) io.ReadCloser {
|
||||
var f decompressor
|
||||
pr, pw := io.Pipe()
|
||||
go func() { pw.CloseWithError(f.decompress(r, pw)) }()
|
||||
return pr
|
||||
f.r = makeReader(r)
|
||||
f.step = (*decompressor).nextBlock
|
||||
return &f
|
||||
}
|
||||
|
||||
// NewReaderDict is like NewReader but initializes the reader
|
||||
@ -639,7 +702,7 @@ func NewReader(r io.Reader) io.ReadCloser {
|
||||
func NewReaderDict(r io.Reader, dict []byte) io.ReadCloser {
|
||||
var f decompressor
|
||||
f.setDict(dict)
|
||||
pr, pw := io.Pipe()
|
||||
go func() { pw.CloseWithError(f.decompress(r, pw)) }()
|
||||
return pr
|
||||
f.r = makeReader(r)
|
||||
f.step = (*decompressor).nextBlock
|
||||
return &f
|
||||
}
|
||||
|
||||
Loading…
Reference in New Issue
Block a user