diff options
Diffstat (limited to 'vendor/github.com/klauspost/compress/flate/gen_inflate.go')
| -rw-r--r-- | vendor/github.com/klauspost/compress/flate/gen_inflate.go | 274 |
1 files changed, 274 insertions, 0 deletions
diff --git a/vendor/github.com/klauspost/compress/flate/gen_inflate.go b/vendor/github.com/klauspost/compress/flate/gen_inflate.go new file mode 100644 index 000000000..c74a95fe7 --- /dev/null +++ b/vendor/github.com/klauspost/compress/flate/gen_inflate.go @@ -0,0 +1,274 @@ +// +build generate + +//go:generate go run $GOFILE && gofmt -w inflate_gen.go + +package main + +import ( + "os" + "strings" +) + +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"} + names := []string{"BytesBuffer", "BytesReader", "BufioReader", "StringsReader"} + imports := []string{"bytes", "bufio", "io", "strings", "math/bits"} + f.WriteString(`// Code generated by go generate gen_inflate.go. DO NOT EDIT. + +package flate + +import ( +`) + + for _, imp := range imports { + f.WriteString("\t\"" + imp + "\"\n") + } + f.WriteString(")\n\n") + + template := ` + +// Decode a single Huffman block from f. +// 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.($TYPE$) + moreBits := func() error { + c, err := fr.ReadByte() + if err != nil { + return noEOF(err) + } + f.roffset++ + f.b |= uint32(c) << f.nb + f.nb += 8 + return nil + } + + 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) + // 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, + // inline call to moreBits and reassign b,nb back to f on return. + nb, b := f.nb, f.b + for { + for nb < n { + c, err := fr.ReadByte() + if err != nil { + f.b = b + f.nb = nb + f.err = noEOF(err) + return + } + f.roffset++ + b |= uint32(c) << (nb & 31) + nb += 8 + } + chunk := f.hl.chunks[b&(huffmanNumChunks-1)] + n = uint(chunk & huffmanCountMask) + if n > huffmanChunkBits { + chunk = f.hl.links[chunk>>huffmanValueShift][(b>>huffmanChunkBits)&f.hl.linkMask] + n = uint(chunk & huffmanCountMask) + } + if n <= nb { + if n == 0 { + f.b = b + f.nb = nb + if debugDecode { + fmt.Println("huffsym: n==0") + } + f.err = CorruptInputError(f.roffset) + return + } + f.b = b >> (n & 31) + f.nb = nb - n + v = int(chunk >> huffmanValueShift) + break + } + } + } + + var n uint // number of bits extra + var length int + var err error + switch { + case v < 256: + f.dict.writeByte(byte(v)) + if f.dict.availWrite() == 0 { + f.toRead = f.dict.readFlush() + f.step = (*decompressor).$FUNCNAME$ + f.stepState = stateInit + return + } + goto readLiteral + case v == 256: + f.finishBlock() + return + // otherwise, reference to older data + case v < 265: + length = v - (257 - 3) + n = 0 + case v < 269: + length = v*2 - (265*2 - 11) + n = 1 + case v < 273: + length = v*4 - (269*4 - 19) + n = 2 + case v < 277: + length = v*8 - (273*8 - 35) + n = 3 + case v < 281: + length = v*16 - (277*16 - 67) + n = 4 + case v < 285: + length = v*32 - (281*32 - 131) + n = 5 + case v < maxNumLit: + length = 258 + n = 0 + default: + if debugDecode { + fmt.Println(v, ">= maxNumLit") + } + f.err = CorruptInputError(f.roffset) + return + } + if n > 0 { + for f.nb < n { + if err = moreBits(); err != nil { + if debugDecode { + fmt.Println("morebits n>0:", err) + } + f.err = err + return + } + } + length += int(f.b & uint32(1<<n-1)) + f.b >>= n + f.nb -= n + } + + var dist int + if f.hd == nil { + for f.nb < 5 { + if err = moreBits(); err != nil { + if debugDecode { + fmt.Println("morebits f.nb<5:", err) + } + f.err = err + return + } + } + dist = int(bits.Reverse8(uint8(f.b & 0x1F << 3))) + f.b >>= 5 + f.nb -= 5 + } else { + if dist, err = f.huffSym(f.hd); err != nil { + if debugDecode { + fmt.Println("huffsym:", err) + } + f.err = err + return + } + } + + 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 + for f.nb < nb { + if err = moreBits(); err != nil { + if debugDecode { + fmt.Println("morebits f.nb<nb:", err) + } + f.err = err + return + } + } + extra |= int(f.b & uint32(1<<nb-1)) + f.b >>= nb + f.nb -= nb + dist = 1<<(nb+1) + 1 + extra + default: + if debugDecode { + fmt.Println("dist too big:", dist, maxNumDist) + } + f.err = CorruptInputError(f.roffset) + return + } + + // No check on length; encoding can be prescient. + if dist > f.dict.histSize() { + if debugDecode { + fmt.Println("dist > f.dict.histSize():", dist, f.dict.histSize()) + } + f.err = CorruptInputError(f.roffset) + return + } + + f.copyLen, f.copyDist = length, dist + goto copyHistory + } + +copyHistory: + // Perform a backwards copy according to RFC section 3.2.3. + { + cnt := f.dict.tryWriteCopy(f.copyDist, f.copyLen) + if cnt == 0 { + cnt = f.dict.writeCopy(f.copyDist, f.copyLen) + } + f.copyLen -= cnt + + if f.dict.availWrite() == 0 || f.copyLen > 0 { + f.toRead = f.dict.readFlush() + f.step = (*decompressor).$FUNCNAME$ // We need to continue this work + f.stepState = stateDict + return + } + goto readLiteral + } +} + +` + 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.huffmanBlockGeneric") + f.WriteString("\t}\n}\n") +} |