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78 lines
1.9 KiB
78 lines
1.9 KiB
package brotli
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/* Copyright 2016 Google Inc. All Rights Reserved.
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Distributed under MIT license.
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See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
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*/
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/* Specification: 7.3. Encoding of the context map */
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const contextMapMaxRle = 16
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/* Specification: 2. Compressed representation overview */
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const maxNumberOfBlockTypes = 256
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/* Specification: 3.3. Alphabet sizes: insert-and-copy length */
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const numLiteralSymbols = 256
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const numCommandSymbols = 704
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const numBlockLenSymbols = 26
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const maxContextMapSymbols = (maxNumberOfBlockTypes + contextMapMaxRle)
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const maxBlockTypeSymbols = (maxNumberOfBlockTypes + 2)
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/* Specification: 3.5. Complex prefix codes */
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const repeatPreviousCodeLength = 16
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const repeatZeroCodeLength = 17
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const codeLengthCodes = (repeatZeroCodeLength + 1)
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/* "code length of 8 is repeated" */
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const initialRepeatedCodeLength = 8
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/* "Large Window Brotli" */
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const largeMaxDistanceBits = 62
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const largeMinWbits = 10
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const largeMaxWbits = 30
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/* Specification: 4. Encoding of distances */
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const numDistanceShortCodes = 16
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const maxNpostfix = 3
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const maxNdirect = 120
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const maxDistanceBits = 24
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func distanceAlphabetSize(NPOSTFIX uint, NDIRECT uint, MAXNBITS uint) uint {
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return numDistanceShortCodes + NDIRECT + uint(MAXNBITS<<(NPOSTFIX+1))
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}
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/* numDistanceSymbols == 1128 */
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const numDistanceSymbols = 1128
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const maxDistance = 0x3FFFFFC
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const maxAllowedDistance = 0x7FFFFFFC
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/* 7.1. Context modes and context ID lookup for literals */
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/* "context IDs for literals are in the range of 0..63" */
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const literalContextBits = 6
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/* 7.2. Context ID for distances */
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const distanceContextBits = 2
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/* 9.1. Format of the Stream Header */
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/* Number of slack bytes for window size. Don't confuse
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with BROTLI_NUM_DISTANCE_SHORT_CODES. */
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const windowGap = 16
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func maxBackwardLimit(W uint) uint {
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return (uint(1) << W) - windowGap
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}
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