mirror of https://github.com/go-gitea/gitea
295 lines
7.2 KiB
Go
295 lines
7.2 KiB
Go
// +build generate
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//go:generate go run $GOFILE && gofmt -w inflate_gen.go
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package main
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import (
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"os"
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"strings"
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)
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func main() {
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f, err := os.Create("inflate_gen.go")
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if err != nil {
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panic(err)
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}
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defer f.Close()
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types := []string{"*bytes.Buffer", "*bytes.Reader", "*bufio.Reader", "*strings.Reader"}
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names := []string{"BytesBuffer", "BytesReader", "BufioReader", "StringsReader"}
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imports := []string{"bytes", "bufio", "io", "strings", "math/bits"}
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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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`)
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for _, imp := range imports {
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f.WriteString("\t\"" + imp + "\"\n")
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}
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f.WriteString(")\n\n")
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template := `
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// Decode a single Huffman block from f.
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// hl and hd are the Huffman states for the lit/length values
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// and the distance values, respectively. If hd == nil, using the
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// fixed distance encoding associated with fixed Huffman blocks.
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func (f *decompressor) $FUNCNAME$() {
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const (
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stateInit = iota // Zero value must be stateInit
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stateDict
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)
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fr := f.r.($TYPE$)
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switch f.stepState {
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case stateInit:
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goto readLiteral
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case stateDict:
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goto copyHistory
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}
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readLiteral:
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// Read literal and/or (length, distance) according to RFC section 3.2.3.
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{
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var v int
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{
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// Inlined v, err := f.huffSym(f.hl)
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// Since a huffmanDecoder can be empty or be composed of a degenerate tree
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// with single element, huffSym must error on these two edge cases. In both
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// cases, the chunks slice will be 0 for the invalid sequence, leading it
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// satisfy the n == 0 check below.
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n := uint(f.hl.maxRead)
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// Optimization. Compiler isn't smart enough to keep f.b,f.nb in registers,
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// but is smart enough to keep local variables in registers, so use nb and b,
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// inline call to moreBits and reassign b,nb back to f on return.
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nb, b := f.nb, f.b
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for {
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for nb < n {
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c, err := fr.ReadByte()
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if err != nil {
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f.b = b
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f.nb = nb
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f.err = noEOF(err)
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return
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}
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f.roffset++
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b |= uint32(c) << (nb & regSizeMaskUint32)
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nb += 8
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}
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chunk := f.hl.chunks[b&(huffmanNumChunks-1)]
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n = uint(chunk & huffmanCountMask)
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if n > huffmanChunkBits {
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chunk = f.hl.links[chunk>>huffmanValueShift][(b>>huffmanChunkBits)&f.hl.linkMask]
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n = uint(chunk & huffmanCountMask)
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}
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if n <= nb {
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if n == 0 {
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f.b = b
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f.nb = nb
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if debugDecode {
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fmt.Println("huffsym: n==0")
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}
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f.err = CorruptInputError(f.roffset)
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return
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}
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f.b = b >> (n & regSizeMaskUint32)
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f.nb = nb - n
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v = int(chunk >> huffmanValueShift)
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break
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}
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}
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}
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var length int
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switch {
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case v < 256:
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f.dict.writeByte(byte(v))
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if f.dict.availWrite() == 0 {
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f.toRead = f.dict.readFlush()
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f.step = (*decompressor).$FUNCNAME$
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f.stepState = stateInit
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return
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}
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goto readLiteral
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case v == 256:
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f.finishBlock()
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return
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// otherwise, reference to older data
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case v < 265:
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length = v - (257 - 3)
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case v < maxNumLit:
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val := decCodeToLen[(v - 257)]
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length = int(val.length) + 3
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n := uint(val.extra)
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for f.nb < n {
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c, err := fr.ReadByte()
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if err != nil {
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if debugDecode {
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fmt.Println("morebits n>0:", err)
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}
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f.err = err
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return
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}
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f.roffset++
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f.b |= uint32(c) << f.nb
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f.nb += 8
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}
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length += int(f.b & uint32(1<<(n®SizeMaskUint32)-1))
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f.b >>= n & regSizeMaskUint32
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f.nb -= n
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default:
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if debugDecode {
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fmt.Println(v, ">= maxNumLit")
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}
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f.err = CorruptInputError(f.roffset)
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return
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}
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var dist uint32
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if f.hd == nil {
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for f.nb < 5 {
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c, err := fr.ReadByte()
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if err != nil {
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if debugDecode {
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fmt.Println("morebits f.nb<5:", err)
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}
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f.err = err
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return
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}
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f.roffset++
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f.b |= uint32(c) << f.nb
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f.nb += 8
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}
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dist = uint32(bits.Reverse8(uint8(f.b & 0x1F << 3)))
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f.b >>= 5
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f.nb -= 5
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} else {
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// Since a huffmanDecoder can be empty or be composed of a degenerate tree
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// with single element, huffSym must error on these two edge cases. In both
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// cases, the chunks slice will be 0 for the invalid sequence, leading it
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// satisfy the n == 0 check below.
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n := uint(f.hd.maxRead)
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// Optimization. Compiler isn't smart enough to keep f.b,f.nb in registers,
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// but is smart enough to keep local variables in registers, so use nb and b,
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// inline call to moreBits and reassign b,nb back to f on return.
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nb, b := f.nb, f.b
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for {
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for nb < n {
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c, err := fr.ReadByte()
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if err != nil {
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f.b = b
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f.nb = nb
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f.err = noEOF(err)
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return
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}
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f.roffset++
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b |= uint32(c) << (nb & regSizeMaskUint32)
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nb += 8
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}
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chunk := f.hd.chunks[b&(huffmanNumChunks-1)]
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n = uint(chunk & huffmanCountMask)
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if n > huffmanChunkBits {
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chunk = f.hd.links[chunk>>huffmanValueShift][(b>>huffmanChunkBits)&f.hd.linkMask]
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n = uint(chunk & huffmanCountMask)
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}
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if n <= nb {
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if n == 0 {
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f.b = b
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f.nb = nb
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if debugDecode {
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fmt.Println("huffsym: n==0")
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}
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f.err = CorruptInputError(f.roffset)
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return
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}
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f.b = b >> (n & regSizeMaskUint32)
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f.nb = nb - n
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dist = uint32(chunk >> huffmanValueShift)
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break
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}
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}
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}
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switch {
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case dist < 4:
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dist++
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case dist < maxNumDist:
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nb := uint(dist-2) >> 1
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// have 1 bit in bottom of dist, need nb more.
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extra := (dist & 1) << (nb & regSizeMaskUint32)
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for f.nb < nb {
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c, err := fr.ReadByte()
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if err != nil {
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if debugDecode {
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fmt.Println("morebits f.nb<nb:", err)
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}
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f.err = err
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return
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}
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f.roffset++
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f.b |= uint32(c) << f.nb
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f.nb += 8
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}
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extra |= f.b & uint32(1<<(nb®SizeMaskUint32)-1)
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f.b >>= nb & regSizeMaskUint32
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f.nb -= nb
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dist = 1<<((nb+1)®SizeMaskUint32) + 1 + extra
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default:
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if debugDecode {
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fmt.Println("dist too big:", dist, maxNumDist)
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}
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f.err = CorruptInputError(f.roffset)
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return
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}
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// No check on length; encoding can be prescient.
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if dist > uint32(f.dict.histSize()) {
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if debugDecode {
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fmt.Println("dist > f.dict.histSize():", dist, f.dict.histSize())
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}
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f.err = CorruptInputError(f.roffset)
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return
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}
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f.copyLen, f.copyDist = length, int(dist)
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goto copyHistory
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}
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copyHistory:
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// Perform a backwards copy according to RFC section 3.2.3.
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{
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cnt := f.dict.tryWriteCopy(f.copyDist, f.copyLen)
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if cnt == 0 {
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cnt = f.dict.writeCopy(f.copyDist, f.copyLen)
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}
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f.copyLen -= cnt
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if f.dict.availWrite() == 0 || f.copyLen > 0 {
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f.toRead = f.dict.readFlush()
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f.step = (*decompressor).$FUNCNAME$ // We need to continue this work
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f.stepState = stateDict
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return
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}
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goto readLiteral
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}
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}
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`
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for i, t := range types {
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s := strings.Replace(template, "$FUNCNAME$", "huffman"+names[i], -1)
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s = strings.Replace(s, "$TYPE$", t, -1)
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f.WriteString(s)
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}
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f.WriteString("func (f *decompressor) huffmanBlockDecoder() func() {\n")
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f.WriteString("\tswitch f.r.(type) {\n")
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for i, t := range types {
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f.WriteString("\t\tcase " + t + ":\n")
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f.WriteString("\t\t\treturn f.huffman" + names[i] + "\n")
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}
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f.WriteString("\t\tdefault:\n")
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f.WriteString("\t\t\treturn f.huffmanBlockGeneric")
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f.WriteString("\t}\n}\n")
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}
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