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compress/flate: use append instead of slice+counter.

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R=rsc, nigeltao
CC=golang-dev
https://golang.org/cl/5561056
This commit is contained in:
Ivan Krasin 2012-01-23 09:26:14 -05:00 committed by Russ Cox
parent d7e34051fc
commit b35cef6704
1 changed files with 13 additions and 18 deletions
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31
src/pkg/compress/flate/deflate.go
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@ -82,9 +82,8 @@ type compressor struct {
blockStart int // window index where current tokens start
byteAvailable bool // if true, still need to process window[index-1].
// queued output tokens: tokens[:ti]
// queued output tokens
tokens []token
ti int
// deflate state
length int
@ -196,12 +195,11 @@ func (d *compressor) initDeflate() {
d.hashPrev = make([]int, windowSize)
d.window = make([]byte, 2*windowSize)
d.hashOffset = 1
d.tokens = make([]token, maxFlateBlockTokens, maxFlateBlockTokens+1)
d.tokens = make([]token, 0, maxFlateBlockTokens+1)
d.length = minMatchLength - 1
d.offset = 0
d.byteAvailable = false
d.index = 0
d.ti = 0
d.hash = 0
d.chainHead = -1
}
@ -233,15 +231,14 @@ Loop:
// Flush current output block if any.
if d.byteAvailable {
// There is still one pending token that needs to be flushed
d.tokens[d.ti] = literalToken(uint32(d.window[d.index-1]))
d.ti++
d.tokens = append(d.tokens, literalToken(uint32(d.window[d.index-1])))
d.byteAvailable = false
}
if d.ti > 0 {
if d.err = d.writeBlock(d.tokens[0:d.ti], d.index, false); d.err != nil {
if len(d.tokens) > 0 {
if d.err = d.writeBlock(d.tokens, d.index, false); d.err != nil {
return
}
d.ti = 0
d.tokens = d.tokens[:0]
}
break Loop
}
@ -275,11 +272,10 @@ Loop:
// There was a match at the previous step, and the current match is
// not better. Output the previous match.
if d.fastSkipHashing != skipNever {
d.tokens[d.ti] = matchToken(uint32(d.length-minMatchLength), uint32(d.offset-minOffsetSize))
d.tokens = append(d.tokens, matchToken(uint32(d.length-minMatchLength), uint32(d.offset-minOffsetSize)))
} else {
d.tokens[d.ti] = matchToken(uint32(prevLength-minMatchLength), uint32(prevOffset-minOffsetSize))
d.tokens = append(d.tokens, matchToken(uint32(prevLength-minMatchLength), uint32(prevOffset-minOffsetSize)))
}
d.ti++
// 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
@ -313,12 +309,12 @@ Loop:
d.hash = (int(d.window[d.index])<<hashShift + int(d.window[d.index+1]))
}
}
if d.ti == maxFlateBlockTokens {
if len(d.tokens) == maxFlateBlockTokens {
// The block includes the current character
if d.err = d.writeBlock(d.tokens, d.index, false); d.err != nil {
return
}
d.ti = 0
d.tokens = d.tokens[:0]
}
} else {
if d.fastSkipHashing != skipNever || d.byteAvailable {
@ -326,13 +322,12 @@ Loop:
if d.fastSkipHashing != skipNever {
i = d.index
}
d.tokens[d.ti] = literalToken(uint32(d.window[i]))
d.ti++
if d.ti == maxFlateBlockTokens {
d.tokens = append(d.tokens, literalToken(uint32(d.window[i])))
if len(d.tokens) == maxFlateBlockTokens {
if d.err = d.writeBlock(d.tokens, i+1, false); d.err != nil {
return
}
d.ti = 0
d.tokens = d.tokens[:0]
}
}
d.index++