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compress/flate: Improve decompression speed
klauspost c00babd
Merge branch 'master' into inflate-improve-speed
klauspost ae9b62a
[klauspost/inflate-improve-speed] * Eliminate length branches
klauspost 161f021
[klauspost/inflate-improve-speed] Fix up comments
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277 changes: 277 additions & 0 deletions
src/compress/flate/gen_inflate.go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,277 @@ | ||
| // Copyright 2020 The Go Authors. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style | ||
| // license that can be found in the LICENSE file. | ||
|
|
||
| // Package flate implements the DEFLATE compressed data format, described in | ||
| // RFC 1951. The gzip and zlib packages implement access to DEFLATE-based file | ||
| // formats. | ||
|
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| //go:build generate | ||
| // +build generate | ||
|
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| //go:generate go run $GOFILE | ||
| //go:generate go fmt inflate_gen.go | ||
|
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||
| package main | ||
|
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||
| import ( | ||
| "os" | ||
| "strings" | ||
| ) | ||
|
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||
| func main() { | ||
| f, err := os.Create("inflate_gen.go") | ||
| if err != nil { | ||
| panic(err) | ||
| } | ||
| defer f.Close() | ||
| types := []string{"*bytes.Buffer", "*bytes.Reader", "*bufio.Reader", "*strings.Reader", "Reader"} | ||
| names := []string{"BytesBuffer", "BytesReader", "BufioReader", "StringsReader", "GenericReader"} | ||
| imports := []string{"bytes", "bufio", "strings", "math/bits"} | ||
| f.WriteString(`// Code generated by go generate gen_inflate.go. DO NOT EDIT. | ||
|
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| package flate | ||
|
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| import ( | ||
| `) | ||
|
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| for _, imp := range imports { | ||
| f.WriteString("\t\"" + imp + "\"\n") | ||
| } | ||
| f.WriteString(")\n\n") | ||
|
|
||
| template := ` | ||
|
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||
| // $FUNCNAME$ decodes a single Huffman block from f. | ||
| // f.r must be a $TYPE$. | ||
| // 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) $FUNCNAME$() { | ||
| const ( | ||
| stateInit = iota // Zero value must be stateInit | ||
| stateDict | ||
| ) | ||
| fr := f.r.($TYPE$) | ||
|
|
||
| // Optimization. Compiler isn't smart enough to keep f.b, f.nb in registers, | ||
| // but is smart enough to keep local variables in registers, so use nb and b, | ||
| // dict reference and reassign b, nb back to f on return. | ||
| fnb, fb, dict := f.nb, f.b, &f.dict | ||
| switch f.stepState { | ||
| case stateInit: | ||
| goto readLiteral | ||
| case stateDict: | ||
| goto copyHistory | ||
| } | ||
|
|
||
| readLiteral: | ||
| // Read literal and/or (length, distance) according to RFC section 3.2.3. | ||
| { | ||
| var v int | ||
| { | ||
| // Inlined v, err := f.huffSym(f.hl) | ||
| // Since a huffmanDecoder can be empty or be composed of a degenerate tree | ||
| // with single element, huffSym must error on these two edge cases. In both | ||
| // cases, the chunks slice will be 0 for the invalid sequence, leading it | ||
| // satisfy the n == 0 check below. | ||
| n := uint(f.hl.maxRead) | ||
| for { | ||
| for fnb < n { | ||
| c, err := fr.ReadByte() | ||
| if err != nil { | ||
| f.b, f.nb = fb, fnb | ||
| f.err = noEOF(err) | ||
| return | ||
| } | ||
| f.roffset++ | ||
| fb |= uint32(c) << (fnb & 31) | ||
| fnb += 8 | ||
| } | ||
| chunk := f.hl.chunks[fb&(huffmanNumChunks-1)] | ||
| n = uint(chunk & huffmanCountMask) | ||
| if n > huffmanChunkBits { | ||
| chunk = f.hl.links[chunk>>huffmanValueShift][(fb>>huffmanChunkBits)&f.hl.linkMask] | ||
| n = uint(chunk & huffmanCountMask) | ||
| } | ||
| if n <= fnb { | ||
| if n == 0 { | ||
| f.b, f.nb = fb, fnb | ||
| f.err = CorruptInputError(f.roffset) | ||
| return | ||
| } | ||
| fb = fb >> (n & 31) | ||
| fnb = fnb - n | ||
| v = int(chunk >> huffmanValueShift) | ||
| break | ||
| } | ||
| } | ||
| } | ||
| var length int | ||
| switch { | ||
| case v < 256: | ||
| dict.writeByte(byte(v)) | ||
| if dict.availWrite() == 0 { | ||
| f.toRead = dict.readFlush() | ||
| f.step = (*decompressor).$FUNCNAME$ | ||
| f.stepState = stateInit | ||
| f.b, f.nb = fb, fnb | ||
| return | ||
| } | ||
| goto readLiteral | ||
| case v == 256: | ||
| f.b, f.nb = fb, fnb | ||
| f.finishBlock() | ||
| return | ||
| // otherwise, reference to older data | ||
| case v < 265: | ||
| // No extra bits | ||
| length = v - (257 - 3) | ||
| case v < maxNumLit: | ||
| val := decCodeToLen[(v - 257)] | ||
| length = int(val.length) + 3 | ||
| n := uint(val.extra) | ||
| for fnb < n { | ||
| c, err := fr.ReadByte() | ||
| if err != nil { | ||
| f.b, f.nb = fb, fnb | ||
| f.err = err | ||
| return | ||
| } | ||
| f.roffset++ | ||
| fb |= uint32(c) << (fnb&31) | ||
| fnb += 8 | ||
| } | ||
| length += int(fb & bitMask32[n]) | ||
| fb >>= n & 31 | ||
| fnb -= n | ||
| default: | ||
| f.err = CorruptInputError(f.roffset) | ||
| f.b, f.nb = fb, fnb | ||
| return | ||
| } | ||
| var dist uint32 | ||
| if f.hd == nil { | ||
| for fnb < 5 { | ||
| c, err := fr.ReadByte() | ||
| if err != nil { | ||
| f.b, f.nb = fb, fnb | ||
| f.err = err | ||
| return | ||
| } | ||
| f.roffset++ | ||
| fb |= uint32(c) << (fnb&31) | ||
| fnb += 8 | ||
| } | ||
| dist = uint32(bits.Reverse8(uint8(fb & 0x1F << 3))) | ||
| fb >>= 5 | ||
| fnb -= 5 | ||
| } else { | ||
| // Since a huffmanDecoder can be empty or be composed of a degenerate tree | ||
| // with single element, huffSym must error on these two edge cases. In both | ||
| // cases, the chunks slice will be 0 for the invalid sequence, leading it | ||
| // satisfy the n == 0 check below. | ||
| n := uint(f.hd.maxRead) | ||
| for { | ||
| for fnb < n { | ||
| c, err := fr.ReadByte() | ||
| if err != nil { | ||
| f.b, f.nb = fb, fnb | ||
| f.err = noEOF(err) | ||
| return | ||
| } | ||
| f.roffset++ | ||
| fb |= uint32(c) << (fnb & 31) | ||
| fnb += 8 | ||
| } | ||
| chunk := f.hd.chunks[fb&(huffmanNumChunks-1)] | ||
| n = uint(chunk & huffmanCountMask) | ||
| if n > huffmanChunkBits { | ||
| chunk = f.hd.links[chunk>>huffmanValueShift][(fb>>huffmanChunkBits)&f.hd.linkMask] | ||
| n = uint(chunk & huffmanCountMask) | ||
| } | ||
| if n <= fnb { | ||
| if n == 0 { | ||
| f.b, f.nb = fb, fnb | ||
| f.err = CorruptInputError(f.roffset) | ||
| return | ||
| } | ||
| fb = fb >> (n & 31) | ||
| fnb = fnb - n | ||
| dist = uint32(chunk >> huffmanValueShift) | ||
| break | ||
| } | ||
| } | ||
| } | ||
| switch { | ||
| case dist < 4: | ||
| dist++ | ||
| case dist < maxNumDist: | ||
| nb := uint(dist-2) >> 1 | ||
| // have 1 bit in bottom of dist, need nb more. | ||
| extra := (dist & 1) << (nb & 31) | ||
| for fnb < nb { | ||
| c, err := fr.ReadByte() | ||
| if err != nil { | ||
| f.b, f.nb = fb, fnb | ||
| f.err = err | ||
| return | ||
| } | ||
| f.roffset++ | ||
| fb |= uint32(c) << (fnb&31) | ||
| fnb += 8 | ||
| } | ||
| extra |= fb & bitMask32[nb] | ||
| fb >>= nb & 31 | ||
| fnb -= nb | ||
| dist = 1<<((nb+1)&31) + 1 + extra | ||
| default: | ||
| f.b, f.nb = fb, fnb | ||
| f.err = CorruptInputError(f.roffset) | ||
| return | ||
| } | ||
| // No check on length; encoding can be prescient. | ||
| if dist > uint32(dict.histSize()) { | ||
| f.b, f.nb = fb, fnb | ||
| f.err = CorruptInputError(f.roffset) | ||
| return | ||
| } | ||
| f.copyLen, f.copyDist = length, int(dist) | ||
| goto copyHistory | ||
| } | ||
| copyHistory: | ||
| // Perform a backwards copy according to RFC section 3.2.3. | ||
| { | ||
| cnt := dict.tryWriteCopy(f.copyDist, f.copyLen) | ||
| if cnt == 0 { | ||
| cnt = dict.writeCopy(f.copyDist, f.copyLen) | ||
| } | ||
| f.copyLen -= cnt | ||
| if dict.availWrite() == 0 || f.copyLen > 0 { | ||
| f.toRead = dict.readFlush() | ||
| f.step = (*decompressor).$FUNCNAME$ // We need to continue this work | ||
| f.stepState = stateDict | ||
| f.b, f.nb = fb, fnb | ||
| return | ||
| } | ||
| goto readLiteral | ||
| } | ||
| // Not reached | ||
| } | ||
|
|
||
| ` | ||
| for i, t := range types { | ||
| s := strings.Replace(template, "$FUNCNAME$", "huffman"+names[i], -1) | ||
| s = strings.Replace(s, "$TYPE$", t, -1) | ||
| f.WriteString(s) | ||
| } | ||
| f.WriteString("func (f *decompressor) huffmanBlockDecoder() func() {\n") | ||
| f.WriteString("\tswitch f.r.(type) {\n") | ||
| for i, t := range types { | ||
| f.WriteString("\t\tcase " + t + ":\n") | ||
| f.WriteString("\t\t\treturn f.huffman" + names[i] + "\n") | ||
| } | ||
| f.WriteString("\t\tdefault:\n") | ||
| f.WriteString("\t\t\treturn f.huffmanGenericReader") | ||
| f.WriteString("\t}\n}\n") | ||
| } |
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