mirror of https://github.com/go-gitea/gitea.git
381 lines
11 KiB
Go
381 lines
11 KiB
Go
// Copyright 2009 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
|
|
|
|
import (
|
|
"bytes"
|
|
"encoding/binary"
|
|
"fmt"
|
|
"io"
|
|
"math"
|
|
)
|
|
|
|
const (
|
|
// From top
|
|
// 2 bits: type 0 = literal 1=EOF 2=Match 3=Unused
|
|
// 8 bits: xlength = length - MIN_MATCH_LENGTH
|
|
// 5 bits offsetcode
|
|
// 16 bits xoffset = offset - MIN_OFFSET_SIZE, or literal
|
|
lengthShift = 22
|
|
offsetMask = 1<<lengthShift - 1
|
|
typeMask = 3 << 30
|
|
literalType = 0 << 30
|
|
matchType = 1 << 30
|
|
matchOffsetOnlyMask = 0xffff
|
|
)
|
|
|
|
// The length code for length X (MIN_MATCH_LENGTH <= X <= MAX_MATCH_LENGTH)
|
|
// is lengthCodes[length - MIN_MATCH_LENGTH]
|
|
var lengthCodes = [256]uint8{
|
|
0, 1, 2, 3, 4, 5, 6, 7, 8, 8,
|
|
9, 9, 10, 10, 11, 11, 12, 12, 12, 12,
|
|
13, 13, 13, 13, 14, 14, 14, 14, 15, 15,
|
|
15, 15, 16, 16, 16, 16, 16, 16, 16, 16,
|
|
17, 17, 17, 17, 17, 17, 17, 17, 18, 18,
|
|
18, 18, 18, 18, 18, 18, 19, 19, 19, 19,
|
|
19, 19, 19, 19, 20, 20, 20, 20, 20, 20,
|
|
20, 20, 20, 20, 20, 20, 20, 20, 20, 20,
|
|
21, 21, 21, 21, 21, 21, 21, 21, 21, 21,
|
|
21, 21, 21, 21, 21, 21, 22, 22, 22, 22,
|
|
22, 22, 22, 22, 22, 22, 22, 22, 22, 22,
|
|
22, 22, 23, 23, 23, 23, 23, 23, 23, 23,
|
|
23, 23, 23, 23, 23, 23, 23, 23, 24, 24,
|
|
24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
|
|
24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
|
|
24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
|
|
25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
|
|
25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
|
|
25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
|
|
25, 25, 26, 26, 26, 26, 26, 26, 26, 26,
|
|
26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
|
|
26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
|
|
26, 26, 26, 26, 27, 27, 27, 27, 27, 27,
|
|
27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
|
|
27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
|
|
27, 27, 27, 27, 27, 28,
|
|
}
|
|
|
|
// lengthCodes1 is length codes, but starting at 1.
|
|
var lengthCodes1 = [256]uint8{
|
|
1, 2, 3, 4, 5, 6, 7, 8, 9, 9,
|
|
10, 10, 11, 11, 12, 12, 13, 13, 13, 13,
|
|
14, 14, 14, 14, 15, 15, 15, 15, 16, 16,
|
|
16, 16, 17, 17, 17, 17, 17, 17, 17, 17,
|
|
18, 18, 18, 18, 18, 18, 18, 18, 19, 19,
|
|
19, 19, 19, 19, 19, 19, 20, 20, 20, 20,
|
|
20, 20, 20, 20, 21, 21, 21, 21, 21, 21,
|
|
21, 21, 21, 21, 21, 21, 21, 21, 21, 21,
|
|
22, 22, 22, 22, 22, 22, 22, 22, 22, 22,
|
|
22, 22, 22, 22, 22, 22, 23, 23, 23, 23,
|
|
23, 23, 23, 23, 23, 23, 23, 23, 23, 23,
|
|
23, 23, 24, 24, 24, 24, 24, 24, 24, 24,
|
|
24, 24, 24, 24, 24, 24, 24, 24, 25, 25,
|
|
25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
|
|
25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
|
|
25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
|
|
26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
|
|
26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
|
|
26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
|
|
26, 26, 27, 27, 27, 27, 27, 27, 27, 27,
|
|
27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
|
|
27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
|
|
27, 27, 27, 27, 28, 28, 28, 28, 28, 28,
|
|
28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
|
|
28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
|
|
28, 28, 28, 28, 28, 29,
|
|
}
|
|
|
|
var offsetCodes = [256]uint32{
|
|
0, 1, 2, 3, 4, 4, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7,
|
|
8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9,
|
|
10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10,
|
|
11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11,
|
|
12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12,
|
|
12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12,
|
|
13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13,
|
|
13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13,
|
|
14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
|
|
14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
|
|
14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
|
|
14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14,
|
|
15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15,
|
|
15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15,
|
|
15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15,
|
|
15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15,
|
|
}
|
|
|
|
// offsetCodes14 are offsetCodes, but with 14 added.
|
|
var offsetCodes14 = [256]uint32{
|
|
14, 15, 16, 17, 18, 18, 19, 19, 20, 20, 20, 20, 21, 21, 21, 21,
|
|
22, 22, 22, 22, 22, 22, 22, 22, 23, 23, 23, 23, 23, 23, 23, 23,
|
|
24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24, 24,
|
|
25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25, 25,
|
|
26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
|
|
26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26,
|
|
27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
|
|
27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27, 27,
|
|
28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
|
|
28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
|
|
28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
|
|
28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28, 28,
|
|
29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
|
|
29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
|
|
29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
|
|
29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29,
|
|
}
|
|
|
|
type token uint32
|
|
|
|
type tokens struct {
|
|
nLits int
|
|
extraHist [32]uint16 // codes 256->maxnumlit
|
|
offHist [32]uint16 // offset codes
|
|
litHist [256]uint16 // codes 0->255
|
|
n uint16 // Must be able to contain maxStoreBlockSize
|
|
tokens [maxStoreBlockSize + 1]token
|
|
}
|
|
|
|
func (t *tokens) Reset() {
|
|
if t.n == 0 {
|
|
return
|
|
}
|
|
t.n = 0
|
|
t.nLits = 0
|
|
for i := range t.litHist[:] {
|
|
t.litHist[i] = 0
|
|
}
|
|
for i := range t.extraHist[:] {
|
|
t.extraHist[i] = 0
|
|
}
|
|
for i := range t.offHist[:] {
|
|
t.offHist[i] = 0
|
|
}
|
|
}
|
|
|
|
func (t *tokens) Fill() {
|
|
if t.n == 0 {
|
|
return
|
|
}
|
|
for i, v := range t.litHist[:] {
|
|
if v == 0 {
|
|
t.litHist[i] = 1
|
|
t.nLits++
|
|
}
|
|
}
|
|
for i, v := range t.extraHist[:literalCount-256] {
|
|
if v == 0 {
|
|
t.nLits++
|
|
t.extraHist[i] = 1
|
|
}
|
|
}
|
|
for i, v := range t.offHist[:offsetCodeCount] {
|
|
if v == 0 {
|
|
t.offHist[i] = 1
|
|
}
|
|
}
|
|
}
|
|
|
|
func indexTokens(in []token) tokens {
|
|
var t tokens
|
|
t.indexTokens(in)
|
|
return t
|
|
}
|
|
|
|
func (t *tokens) indexTokens(in []token) {
|
|
t.Reset()
|
|
for _, tok := range in {
|
|
if tok < matchType {
|
|
t.AddLiteral(tok.literal())
|
|
continue
|
|
}
|
|
t.AddMatch(uint32(tok.length()), tok.offset()&matchOffsetOnlyMask)
|
|
}
|
|
}
|
|
|
|
// emitLiteral writes a literal chunk and returns the number of bytes written.
|
|
func emitLiteral(dst *tokens, lit []byte) {
|
|
ol := int(dst.n)
|
|
for i, v := range lit {
|
|
dst.tokens[(i+ol)&maxStoreBlockSize] = token(v)
|
|
dst.litHist[v]++
|
|
}
|
|
dst.n += uint16(len(lit))
|
|
dst.nLits += len(lit)
|
|
}
|
|
|
|
func (t *tokens) AddLiteral(lit byte) {
|
|
t.tokens[t.n] = token(lit)
|
|
t.litHist[lit]++
|
|
t.n++
|
|
t.nLits++
|
|
}
|
|
|
|
// from https://stackoverflow.com/a/28730362
|
|
func mFastLog2(val float32) float32 {
|
|
ux := int32(math.Float32bits(val))
|
|
log2 := (float32)(((ux >> 23) & 255) - 128)
|
|
ux &= -0x7f800001
|
|
ux += 127 << 23
|
|
uval := math.Float32frombits(uint32(ux))
|
|
log2 += ((-0.34484843)*uval+2.02466578)*uval - 0.67487759
|
|
return log2
|
|
}
|
|
|
|
// EstimatedBits will return an minimum size estimated by an *optimal*
|
|
// compression of the block.
|
|
// The size of the block
|
|
func (t *tokens) EstimatedBits() int {
|
|
shannon := float32(0)
|
|
bits := int(0)
|
|
nMatches := 0
|
|
if t.nLits > 0 {
|
|
invTotal := 1.0 / float32(t.nLits)
|
|
for _, v := range t.litHist[:] {
|
|
if v > 0 {
|
|
n := float32(v)
|
|
shannon += atLeastOne(-mFastLog2(n*invTotal)) * n
|
|
}
|
|
}
|
|
// Just add 15 for EOB
|
|
shannon += 15
|
|
for i, v := range t.extraHist[1 : literalCount-256] {
|
|
if v > 0 {
|
|
n := float32(v)
|
|
shannon += atLeastOne(-mFastLog2(n*invTotal)) * n
|
|
bits += int(lengthExtraBits[i&31]) * int(v)
|
|
nMatches += int(v)
|
|
}
|
|
}
|
|
}
|
|
if nMatches > 0 {
|
|
invTotal := 1.0 / float32(nMatches)
|
|
for i, v := range t.offHist[:offsetCodeCount] {
|
|
if v > 0 {
|
|
n := float32(v)
|
|
shannon += atLeastOne(-mFastLog2(n*invTotal)) * n
|
|
bits += int(offsetExtraBits[i&31]) * int(v)
|
|
}
|
|
}
|
|
}
|
|
return int(shannon) + bits
|
|
}
|
|
|
|
// AddMatch adds a match to the tokens.
|
|
// This function is very sensitive to inlining and right on the border.
|
|
func (t *tokens) AddMatch(xlength uint32, xoffset uint32) {
|
|
if debugDeflate {
|
|
if xlength >= maxMatchLength+baseMatchLength {
|
|
panic(fmt.Errorf("invalid length: %v", xlength))
|
|
}
|
|
if xoffset >= maxMatchOffset+baseMatchOffset {
|
|
panic(fmt.Errorf("invalid offset: %v", xoffset))
|
|
}
|
|
}
|
|
oCode := offsetCode(xoffset)
|
|
xoffset |= oCode << 16
|
|
t.nLits++
|
|
|
|
t.extraHist[lengthCodes1[uint8(xlength)]]++
|
|
t.offHist[oCode]++
|
|
t.tokens[t.n] = token(matchType | xlength<<lengthShift | xoffset)
|
|
t.n++
|
|
}
|
|
|
|
// AddMatchLong adds a match to the tokens, potentially longer than max match length.
|
|
// Length should NOT have the base subtracted, only offset should.
|
|
func (t *tokens) AddMatchLong(xlength int32, xoffset uint32) {
|
|
if debugDeflate {
|
|
if xoffset >= maxMatchOffset+baseMatchOffset {
|
|
panic(fmt.Errorf("invalid offset: %v", xoffset))
|
|
}
|
|
}
|
|
oc := offsetCode(xoffset)
|
|
xoffset |= oc << 16
|
|
for xlength > 0 {
|
|
xl := xlength
|
|
if xl > 258 {
|
|
// We need to have at least baseMatchLength left over for next loop.
|
|
xl = 258 - baseMatchLength
|
|
}
|
|
xlength -= xl
|
|
xl -= baseMatchLength
|
|
t.nLits++
|
|
t.extraHist[lengthCodes1[uint8(xl)]]++
|
|
t.offHist[oc]++
|
|
t.tokens[t.n] = token(matchType | uint32(xl)<<lengthShift | xoffset)
|
|
t.n++
|
|
}
|
|
}
|
|
|
|
func (t *tokens) AddEOB() {
|
|
t.tokens[t.n] = token(endBlockMarker)
|
|
t.extraHist[0]++
|
|
t.n++
|
|
}
|
|
|
|
func (t *tokens) Slice() []token {
|
|
return t.tokens[:t.n]
|
|
}
|
|
|
|
// VarInt returns the tokens as varint encoded bytes.
|
|
func (t *tokens) VarInt() []byte {
|
|
var b = make([]byte, binary.MaxVarintLen32*int(t.n))
|
|
var off int
|
|
for _, v := range t.tokens[:t.n] {
|
|
off += binary.PutUvarint(b[off:], uint64(v))
|
|
}
|
|
return b[:off]
|
|
}
|
|
|
|
// FromVarInt restores t to the varint encoded tokens provided.
|
|
// Any data in t is removed.
|
|
func (t *tokens) FromVarInt(b []byte) error {
|
|
var buf = bytes.NewReader(b)
|
|
var toks []token
|
|
for {
|
|
r, err := binary.ReadUvarint(buf)
|
|
if err == io.EOF {
|
|
break
|
|
}
|
|
if err != nil {
|
|
return err
|
|
}
|
|
toks = append(toks, token(r))
|
|
}
|
|
t.indexTokens(toks)
|
|
return nil
|
|
}
|
|
|
|
// Returns the type of a token
|
|
func (t token) typ() uint32 { return uint32(t) & typeMask }
|
|
|
|
// Returns the literal of a literal token
|
|
func (t token) literal() uint8 { return uint8(t) }
|
|
|
|
// Returns the extra offset of a match token
|
|
func (t token) offset() uint32 { return uint32(t) & offsetMask }
|
|
|
|
func (t token) length() uint8 { return uint8(t >> lengthShift) }
|
|
|
|
// The code is never more than 8 bits, but is returned as uint32 for convenience.
|
|
func lengthCode(len uint8) uint32 { return uint32(lengthCodes[len]) }
|
|
|
|
// Returns the offset code corresponding to a specific offset
|
|
func offsetCode(off uint32) uint32 {
|
|
if false {
|
|
if off < uint32(len(offsetCodes)) {
|
|
return offsetCodes[off&255]
|
|
} else if off>>7 < uint32(len(offsetCodes)) {
|
|
return offsetCodes[(off>>7)&255] + 14
|
|
} else {
|
|
return offsetCodes[(off>>14)&255] + 28
|
|
}
|
|
}
|
|
if off < uint32(len(offsetCodes)) {
|
|
return offsetCodes[uint8(off)]
|
|
}
|
|
return offsetCodes14[uint8(off>>7)]
|
|
}
|