// 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 } }