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115 lines
4.1 KiB
115 lines
4.1 KiB
// Copyright 2009 The Go Authors. All rights reserved. |
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// Use of this source code is governed by a BSD-style |
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// license that can be found in the LICENSE file. |
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package flate |
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import "fmt" |
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const ( |
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// 2 bits: type 0 = literal 1=EOF 2=Match 3=Unused |
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// 8 bits: xlength = length - MIN_MATCH_LENGTH |
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// 22 bits xoffset = offset - MIN_OFFSET_SIZE, or literal |
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lengthShift = 22 |
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offsetMask = 1<<lengthShift - 1 |
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typeMask = 3 << 30 |
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literalType = 0 << 30 |
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matchType = 1 << 30 |
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) |
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// The length code for length X (MIN_MATCH_LENGTH <= X <= MAX_MATCH_LENGTH) |
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// is lengthCodes[length - MIN_MATCH_LENGTH] |
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var lengthCodes = [...]uint32{ |
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0, 1, 2, 3, 4, 5, 6, 7, 8, 8, |
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9, 9, 10, 10, 11, 11, 12, 12, 12, 12, |
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13, 13, 13, 13, 14, 14, 14, 14, 15, 15, |
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15, 15, 16, 16, 16, 16, 16, 16, 16, 16, |
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17, 17, 17, 17, 17, 17, 17, 17, 18, 18, |
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18, 18, 18, 18, 18, 18, 19, 19, 19, 19, |
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19, 19, 19, 19, 20, 20, 20, 20, 20, 20, |
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20, 20, 20, 20, 20, 20, 20, 20, 20, 20, |
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21, 21, 21, 21, 21, 21, 21, 21, 21, 21, |
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21, 21, 21, 21, 21, 21, 22, 22, 22, 22, |
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22, 22, 22, 22, 22, 22, 22, 22, 22, 22, |
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22, 22, 23, 23, 23, 23, 23, 23, 23, 23, |
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23, 23, 23, 23, 23, 23, 23, 23, 24, 24, |
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24, 24, 24, 24, 24, 24, 24, 24, 24, 24, |
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24, 24, 24, 24, 24, 24, 24, 24, 24, 24, |
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24, 24, 24, 24, 24, 24, 24, 24, 24, 24, |
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25, 25, 25, 25, 25, 25, 25, 25, 25, 25, |
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25, 25, 25, 25, 25, 25, 25, 25, 25, 25, |
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25, 25, 25, 25, 25, 25, 25, 25, 25, 25, |
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25, 25, 26, 26, 26, 26, 26, 26, 26, 26, |
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26, 26, 26, 26, 26, 26, 26, 26, 26, 26, |
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26, 26, 26, 26, 26, 26, 26, 26, 26, 26, |
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26, 26, 26, 26, 27, 27, 27, 27, 27, 27, |
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27, 27, 27, 27, 27, 27, 27, 27, 27, 27, |
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27, 27, 27, 27, 27, 27, 27, 27, 27, 27, |
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27, 27, 27, 27, 27, 28, |
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} |
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var offsetCodes = [...]uint32{ |
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0, 1, 2, 3, 4, 4, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, |
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8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, |
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10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, |
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11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, |
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12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, |
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12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, |
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13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, |
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13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, |
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14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, |
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14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, |
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14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, |
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14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, |
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15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, |
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15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, |
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15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, |
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15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, 15, |
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} |
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type token uint32 |
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type tokens struct { |
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tokens [maxStoreBlockSize + 1]token |
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n uint16 // Must be able to contain maxStoreBlockSize |
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} |
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// Convert a literal into a literal token. |
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func literalToken(literal uint32) token { return token(literalType + literal) } |
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// Convert a < xlength, xoffset > pair into a match token. |
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func matchToken(xlength uint32, xoffset uint32) token { |
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return token(matchType + xlength<<lengthShift + xoffset) |
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} |
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func matchTokend(xlength uint32, xoffset uint32) token { |
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if xlength > maxMatchLength || xoffset > maxMatchOffset { |
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panic(fmt.Sprintf("Invalid match: len: %d, offset: %d\n", xlength, xoffset)) |
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return token(matchType) |
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} |
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return token(matchType + xlength<<lengthShift + xoffset) |
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} |
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// Returns the type of a token |
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func (t token) typ() uint32 { return uint32(t) & typeMask } |
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// Returns the literal of a literal token |
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func (t token) literal() uint32 { return uint32(t - literalType) } |
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// Returns the extra offset of a match token |
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func (t token) offset() uint32 { return uint32(t) & offsetMask } |
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func (t token) length() uint32 { return uint32((t - matchType) >> lengthShift) } |
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func lengthCode(len uint32) uint32 { return lengthCodes[len] } |
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// Returns the offset code corresponding to a specific offset |
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func offsetCode(off uint32) uint32 { |
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if off < uint32(len(offsetCodes)) { |
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return offsetCodes[off] |
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} else if off>>7 < uint32(len(offsetCodes)) { |
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return offsetCodes[off>>7] + 14 |
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} else { |
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return offsetCodes[off>>14] + 28 |
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} |
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}
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