mirror of
https://codeberg.org/forgejo/forgejo.git
synced 2024-11-06 01:09:33 +00:00
115 lines
4.1 KiB
Go
115 lines
4.1 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 "fmt"
|
|
|
|
const (
|
|
// 2 bits: type 0 = literal 1=EOF 2=Match 3=Unused
|
|
// 8 bits: xlength = length - MIN_MATCH_LENGTH
|
|
// 22 bits xoffset = offset - MIN_OFFSET_SIZE, or literal
|
|
lengthShift = 22
|
|
offsetMask = 1<<lengthShift - 1
|
|
typeMask = 3 << 30
|
|
literalType = 0 << 30
|
|
matchType = 1 << 30
|
|
)
|
|
|
|
// The length code for length X (MIN_MATCH_LENGTH <= X <= MAX_MATCH_LENGTH)
|
|
// is lengthCodes[length - MIN_MATCH_LENGTH]
|
|
var lengthCodes = [...]uint32{
|
|
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,
|
|
}
|
|
|
|
var offsetCodes = [...]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,
|
|
}
|
|
|
|
type token uint32
|
|
|
|
type tokens struct {
|
|
tokens [maxStoreBlockSize + 1]token
|
|
n uint16 // Must be able to contain maxStoreBlockSize
|
|
}
|
|
|
|
// Convert a literal into a literal token.
|
|
func literalToken(literal uint32) token { return token(literalType + literal) }
|
|
|
|
// Convert a < xlength, xoffset > pair into a match token.
|
|
func matchToken(xlength uint32, xoffset uint32) token {
|
|
return token(matchType + xlength<<lengthShift + xoffset)
|
|
}
|
|
|
|
func matchTokend(xlength uint32, xoffset uint32) token {
|
|
if xlength > maxMatchLength || xoffset > maxMatchOffset {
|
|
panic(fmt.Sprintf("Invalid match: len: %d, offset: %d\n", xlength, xoffset))
|
|
return token(matchType)
|
|
}
|
|
return token(matchType + xlength<<lengthShift + xoffset)
|
|
}
|
|
|
|
// 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() uint32 { return uint32(t - literalType) }
|
|
|
|
// Returns the extra offset of a match token
|
|
func (t token) offset() uint32 { return uint32(t) & offsetMask }
|
|
|
|
func (t token) length() uint32 { return uint32((t - matchType) >> lengthShift) }
|
|
|
|
func lengthCode(len uint32) uint32 { return lengthCodes[len] }
|
|
|
|
// Returns the offset code corresponding to a specific offset
|
|
func offsetCode(off uint32) uint32 {
|
|
if off < uint32(len(offsetCodes)) {
|
|
return offsetCodes[off]
|
|
} else if off>>7 < uint32(len(offsetCodes)) {
|
|
return offsetCodes[off>>7] + 14
|
|
} else {
|
|
return offsetCodes[off>>14] + 28
|
|
}
|
|
}
|