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| // 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
|
| 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
|
| // 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)
| }
|
| // 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]
| }
| if off>>7 < uint32(len(offsetCodes)) {
| return offsetCodes[off>>7] + 14
| }
| return offsetCodes[off>>14] + 28
| }
|
|
