1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294
|
// +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", "fmt", "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.($TYPE$)
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 & regSizeMaskUint32)
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 & regSizeMaskUint32)
f.nb = nb - n
v = int(chunk >> huffmanValueShift)
break
}
}
}
var length int
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)
case v < maxNumLit:
val := decCodeToLen[(v - 257)]
length = int(val.length) + 3
n := uint(val.extra)
for f.nb < n {
c, err := fr.ReadByte()
if err != nil {
if debugDecode {
fmt.Println("morebits n>0:", err)
}
f.err = err
return
}
f.roffset++
f.b |= uint32(c) << f.nb
f.nb += 8
}
length += int(f.b & uint32(1<<(n®SizeMaskUint32)-1))
f.b >>= n & regSizeMaskUint32
f.nb -= n
default:
if debugDecode {
fmt.Println(v, ">= maxNumLit")
}
f.err = CorruptInputError(f.roffset)
return
}
var dist uint32
if f.hd == nil {
for f.nb < 5 {
c, err := fr.ReadByte()
if err != nil {
if debugDecode {
fmt.Println("morebits f.nb<5:", err)
}
f.err = err
return
}
f.roffset++
f.b |= uint32(c) << f.nb
f.nb += 8
}
dist = uint32(bits.Reverse8(uint8(f.b & 0x1F << 3)))
f.b >>= 5
f.nb -= 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)
// 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 & regSizeMaskUint32)
nb += 8
}
chunk := f.hd.chunks[b&(huffmanNumChunks-1)]
n = uint(chunk & huffmanCountMask)
if n > huffmanChunkBits {
chunk = f.hd.links[chunk>>huffmanValueShift][(b>>huffmanChunkBits)&f.hd.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 & regSizeMaskUint32)
f.nb = nb - 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 & regSizeMaskUint32)
for f.nb < nb {
c, err := fr.ReadByte()
if err != nil {
if debugDecode {
fmt.Println("morebits f.nb<nb:", err)
}
f.err = err
return
}
f.roffset++
f.b |= uint32(c) << f.nb
f.nb += 8
}
extra |= f.b & uint32(1<<(nb®SizeMaskUint32)-1)
f.b >>= nb & regSizeMaskUint32
f.nb -= nb
dist = 1<<((nb+1)®SizeMaskUint32) + 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 > uint32(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, int(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")
}
|