diff options
Diffstat (limited to 'vendor/github.com/andybalholm/brotli/huffman.go')
| -rw-r--r-- | vendor/github.com/andybalholm/brotli/huffman.go | 653 |
1 files changed, 653 insertions, 0 deletions
diff --git a/vendor/github.com/andybalholm/brotli/huffman.go b/vendor/github.com/andybalholm/brotli/huffman.go new file mode 100644 index 0000000000..182f3d2a55 --- /dev/null +++ b/vendor/github.com/andybalholm/brotli/huffman.go @@ -0,0 +1,653 @@ +package brotli + +/* Copyright 2013 Google Inc. All Rights Reserved. + + Distributed under MIT license. + See file LICENSE for detail or copy at https://opensource.org/licenses/MIT +*/ + +/* Utilities for building Huffman decoding tables. */ + +const huffmanMaxCodeLength = 15 + +/* Maximum possible Huffman table size for an alphabet size of (index * 32), + max code length 15 and root table bits 8. */ +var kMaxHuffmanTableSize = []uint16{ + 256, + 402, + 436, + 468, + 500, + 534, + 566, + 598, + 630, + 662, + 694, + 726, + 758, + 790, + 822, + 854, + 886, + 920, + 952, + 984, + 1016, + 1048, + 1080, + 1112, + 1144, + 1176, + 1208, + 1240, + 1272, + 1304, + 1336, + 1368, + 1400, + 1432, + 1464, + 1496, + 1528, +} + +/* BROTLI_NUM_BLOCK_LEN_SYMBOLS == 26 */ +const huffmanMaxSize26 = 396 + +/* BROTLI_MAX_BLOCK_TYPE_SYMBOLS == 258 */ +const huffmanMaxSize258 = 632 + +/* BROTLI_MAX_CONTEXT_MAP_SYMBOLS == 272 */ +const huffmanMaxSize272 = 646 + +const huffmanMaxCodeLengthCodeLength = 5 + +/* Do not create this struct directly - use the ConstructHuffmanCode + * constructor below! */ +type huffmanCode struct { + bits byte + value uint16 +} + +func constructHuffmanCode(bits byte, value uint16) huffmanCode { + var h huffmanCode + h.bits = bits + h.value = value + return h +} + +/* Builds Huffman lookup table assuming code lengths are in symbol order. */ + +/* Builds Huffman lookup table assuming code lengths are in symbol order. + Returns size of resulting table. */ + +/* Builds a simple Huffman table. The |num_symbols| parameter is to be + interpreted as follows: 0 means 1 symbol, 1 means 2 symbols, + 2 means 3 symbols, 3 means 4 symbols with lengths [2, 2, 2, 2], + 4 means 4 symbols with lengths [1, 2, 3, 3]. */ + +/* Contains a collection of Huffman trees with the same alphabet size. */ +/* max_symbol is needed due to simple codes since log2(alphabet_size) could be + greater than log2(max_symbol). */ +type huffmanTreeGroup struct { + htrees [][]huffmanCode + codes []huffmanCode + alphabet_size uint16 + max_symbol uint16 + num_htrees uint16 +} + +const reverseBitsMax = 8 + +const reverseBitsBase = 0 + +var kReverseBits = [1 << reverseBitsMax]byte{ + 0x00, + 0x80, + 0x40, + 0xC0, + 0x20, + 0xA0, + 0x60, + 0xE0, + 0x10, + 0x90, + 0x50, + 0xD0, + 0x30, + 0xB0, + 0x70, + 0xF0, + 0x08, + 0x88, + 0x48, + 0xC8, + 0x28, + 0xA8, + 0x68, + 0xE8, + 0x18, + 0x98, + 0x58, + 0xD8, + 0x38, + 0xB8, + 0x78, + 0xF8, + 0x04, + 0x84, + 0x44, + 0xC4, + 0x24, + 0xA4, + 0x64, + 0xE4, + 0x14, + 0x94, + 0x54, + 0xD4, + 0x34, + 0xB4, + 0x74, + 0xF4, + 0x0C, + 0x8C, + 0x4C, + 0xCC, + 0x2C, + 0xAC, + 0x6C, + 0xEC, + 0x1C, + 0x9C, + 0x5C, + 0xDC, + 0x3C, + 0xBC, + 0x7C, + 0xFC, + 0x02, + 0x82, + 0x42, + 0xC2, + 0x22, + 0xA2, + 0x62, + 0xE2, + 0x12, + 0x92, + 0x52, + 0xD2, + 0x32, + 0xB2, + 0x72, + 0xF2, + 0x0A, + 0x8A, + 0x4A, + 0xCA, + 0x2A, + 0xAA, + 0x6A, + 0xEA, + 0x1A, + 0x9A, + 0x5A, + 0xDA, + 0x3A, + 0xBA, + 0x7A, + 0xFA, + 0x06, + 0x86, + 0x46, + 0xC6, + 0x26, + 0xA6, + 0x66, + 0xE6, + 0x16, + 0x96, + 0x56, + 0xD6, + 0x36, + 0xB6, + 0x76, + 0xF6, + 0x0E, + 0x8E, + 0x4E, + 0xCE, + 0x2E, + 0xAE, + 0x6E, + 0xEE, + 0x1E, + 0x9E, + 0x5E, + 0xDE, + 0x3E, + 0xBE, + 0x7E, + 0xFE, + 0x01, + 0x81, + 0x41, + 0xC1, + 0x21, + 0xA1, + 0x61, + 0xE1, + 0x11, + 0x91, + 0x51, + 0xD1, + 0x31, + 0xB1, + 0x71, + 0xF1, + 0x09, + 0x89, + 0x49, + 0xC9, + 0x29, + 0xA9, + 0x69, + 0xE9, + 0x19, + 0x99, + 0x59, + 0xD9, + 0x39, + 0xB9, + 0x79, + 0xF9, + 0x05, + 0x85, + 0x45, + 0xC5, + 0x25, + 0xA5, + 0x65, + 0xE5, + 0x15, + 0x95, + 0x55, + 0xD5, + 0x35, + 0xB5, + 0x75, + 0xF5, + 0x0D, + 0x8D, + 0x4D, + 0xCD, + 0x2D, + 0xAD, + 0x6D, + 0xED, + 0x1D, + 0x9D, + 0x5D, + 0xDD, + 0x3D, + 0xBD, + 0x7D, + 0xFD, + 0x03, + 0x83, + 0x43, + 0xC3, + 0x23, + 0xA3, + 0x63, + 0xE3, + 0x13, + 0x93, + 0x53, + 0xD3, + 0x33, + 0xB3, + 0x73, + 0xF3, + 0x0B, + 0x8B, + 0x4B, + 0xCB, + 0x2B, + 0xAB, + 0x6B, + 0xEB, + 0x1B, + 0x9B, + 0x5B, + 0xDB, + 0x3B, + 0xBB, + 0x7B, + 0xFB, + 0x07, + 0x87, + 0x47, + 0xC7, + 0x27, + 0xA7, + 0x67, + 0xE7, + 0x17, + 0x97, + 0x57, + 0xD7, + 0x37, + 0xB7, + 0x77, + 0xF7, + 0x0F, + 0x8F, + 0x4F, + 0xCF, + 0x2F, + 0xAF, + 0x6F, + 0xEF, + 0x1F, + 0x9F, + 0x5F, + 0xDF, + 0x3F, + 0xBF, + 0x7F, + 0xFF, +} + +const reverseBitsLowest = (uint64(1) << (reverseBitsMax - 1 + reverseBitsBase)) + +/* Returns reverse(num >> BROTLI_REVERSE_BITS_BASE, BROTLI_REVERSE_BITS_MAX), + where reverse(value, len) is the bit-wise reversal of the len least + significant bits of value. */ +func reverseBits8(num uint64) uint64 { + return uint64(kReverseBits[num]) +} + +/* Stores code in table[0], table[step], table[2*step], ..., table[end] */ +/* Assumes that end is an integer multiple of step */ +func replicateValue(table []huffmanCode, step int, end int, code huffmanCode) { + for { + end -= step + table[end] = code + if end <= 0 { + break + } + } +} + +/* Returns the table width of the next 2nd level table. |count| is the histogram + of bit lengths for the remaining symbols, |len| is the code length of the + next processed symbol. */ +func nextTableBitSize(count []uint16, len int, root_bits int) int { + var left int = 1 << uint(len-root_bits) + for len < huffmanMaxCodeLength { + left -= int(count[len]) + if left <= 0 { + break + } + len++ + left <<= 1 + } + + return len - root_bits +} + +func buildCodeLengthsHuffmanTable(table []huffmanCode, code_lengths []byte, count []uint16) { + var code huffmanCode /* current table entry */ /* symbol index in original or sorted table */ /* prefix code */ /* prefix code addend */ /* step size to replicate values in current table */ /* size of current table */ /* symbols sorted by code length */ + var symbol int + var key uint64 + var key_step uint64 + var step int + var table_size int + var sorted [codeLengthCodes]int + var offset [huffmanMaxCodeLengthCodeLength + 1]int + var bits int + var bits_count int + /* offsets in sorted table for each length */ + assert(huffmanMaxCodeLengthCodeLength <= reverseBitsMax) + + /* Generate offsets into sorted symbol table by code length. */ + symbol = -1 + + bits = 1 + var i int + for i = 0; i < huffmanMaxCodeLengthCodeLength; i++ { + symbol += int(count[bits]) + offset[bits] = symbol + bits++ + } + + /* Symbols with code length 0 are placed after all other symbols. */ + offset[0] = codeLengthCodes - 1 + + /* Sort symbols by length, by symbol order within each length. */ + symbol = codeLengthCodes + + for { + var i int + for i = 0; i < 6; i++ { + symbol-- + sorted[offset[code_lengths[symbol]]] = symbol + offset[code_lengths[symbol]]-- + } + if symbol == 0 { + break + } + } + + table_size = 1 << huffmanMaxCodeLengthCodeLength + + /* Special case: all symbols but one have 0 code length. */ + if offset[0] == 0 { + code = constructHuffmanCode(0, uint16(sorted[0])) + for key = 0; key < uint64(table_size); key++ { + table[key] = code + } + + return + } + + /* Fill in table. */ + key = 0 + + key_step = reverseBitsLowest + symbol = 0 + bits = 1 + step = 2 + for { + for bits_count = int(count[bits]); bits_count != 0; bits_count-- { + code = constructHuffmanCode(byte(bits), uint16(sorted[symbol])) + symbol++ + replicateValue(table[reverseBits8(key):], step, table_size, code) + key += key_step + } + + step <<= 1 + key_step >>= 1 + bits++ + if bits > huffmanMaxCodeLengthCodeLength { + break + } + } +} + +func buildHuffmanTable(root_table []huffmanCode, root_bits int, symbol_lists symbolList, count []uint16) uint32 { + var code huffmanCode /* current table entry */ /* next available space in table */ /* current code length */ /* symbol index in original or sorted table */ /* prefix code */ /* prefix code addend */ /* 2nd level table prefix code */ /* 2nd level table prefix code addend */ /* step size to replicate values in current table */ /* key length of current table */ /* size of current table */ /* sum of root table size and 2nd level table sizes */ + var table []huffmanCode + var len int + var symbol int + var key uint64 + var key_step uint64 + var sub_key uint64 + var sub_key_step uint64 + var step int + var table_bits int + var table_size int + var total_size int + var max_length int = -1 + var bits int + var bits_count int + + assert(root_bits <= reverseBitsMax) + assert(huffmanMaxCodeLength-root_bits <= reverseBitsMax) + + for symbolListGet(symbol_lists, max_length) == 0xFFFF { + max_length-- + } + max_length += huffmanMaxCodeLength + 1 + + table = root_table + table_bits = root_bits + table_size = 1 << uint(table_bits) + total_size = table_size + + /* Fill in the root table. Reduce the table size to if possible, + and create the repetitions by memcpy. */ + if table_bits > max_length { + table_bits = max_length + table_size = 1 << uint(table_bits) + } + + key = 0 + key_step = reverseBitsLowest + bits = 1 + step = 2 + for { + symbol = bits - (huffmanMaxCodeLength + 1) + for bits_count = int(count[bits]); bits_count != 0; bits_count-- { + symbol = int(symbolListGet(symbol_lists, symbol)) + code = constructHuffmanCode(byte(bits), uint16(symbol)) + replicateValue(table[reverseBits8(key):], step, table_size, code) + key += key_step + } + + step <<= 1 + key_step >>= 1 + bits++ + if bits > table_bits { + break + } + } + + /* If root_bits != table_bits then replicate to fill the remaining slots. */ + for total_size != table_size { + copy(table[table_size:], table[:uint(table_size)]) + table_size <<= 1 + } + + /* Fill in 2nd level tables and add pointers to root table. */ + key_step = reverseBitsLowest >> uint(root_bits-1) + + sub_key = reverseBitsLowest << 1 + sub_key_step = reverseBitsLowest + len = root_bits + 1 + step = 2 + for ; len <= max_length; len++ { + symbol = len - (huffmanMaxCodeLength + 1) + for ; count[len] != 0; count[len]-- { + if sub_key == reverseBitsLowest<<1 { + table = table[table_size:] + table_bits = nextTableBitSize(count, int(len), root_bits) + table_size = 1 << uint(table_bits) + total_size += table_size + sub_key = reverseBits8(key) + key += key_step + root_table[sub_key] = constructHuffmanCode(byte(table_bits+root_bits), uint16(uint64(uint(-cap(table)+cap(root_table)))-sub_key)) + sub_key = 0 + } + + symbol = int(symbolListGet(symbol_lists, symbol)) + code = constructHuffmanCode(byte(len-root_bits), uint16(symbol)) + replicateValue(table[reverseBits8(sub_key):], step, table_size, code) + sub_key += sub_key_step + } + + step <<= 1 + sub_key_step >>= 1 + } + + return uint32(total_size) +} + +func buildSimpleHuffmanTable(table []huffmanCode, root_bits int, val []uint16, num_symbols uint32) uint32 { + var table_size uint32 = 1 + var goal_size uint32 = 1 << uint(root_bits) + switch num_symbols { + case 0: + table[0] = constructHuffmanCode(0, val[0]) + + case 1: + if val[1] > val[0] { + table[0] = constructHuffmanCode(1, val[0]) + table[1] = constructHuffmanCode(1, val[1]) + } else { + table[0] = constructHuffmanCode(1, val[1]) + table[1] = constructHuffmanCode(1, val[0]) + } + + table_size = 2 + + case 2: + table[0] = constructHuffmanCode(1, val[0]) + table[2] = constructHuffmanCode(1, val[0]) + if val[2] > val[1] { + table[1] = constructHuffmanCode(2, val[1]) + table[3] = constructHuffmanCode(2, val[2]) + } else { + table[1] = constructHuffmanCode(2, val[2]) + table[3] = constructHuffmanCode(2, val[1]) + } + + table_size = 4 + + case 3: + var i int + var k int + for i = 0; i < 3; i++ { + for k = i + 1; k < 4; k++ { + if val[k] < val[i] { + var t uint16 = val[k] + val[k] = val[i] + val[i] = t + } + } + } + + table[0] = constructHuffmanCode(2, val[0]) + table[2] = constructHuffmanCode(2, val[1]) + table[1] = constructHuffmanCode(2, val[2]) + table[3] = constructHuffmanCode(2, val[3]) + table_size = 4 + + case 4: + if val[3] < val[2] { + var t uint16 = val[3] + val[3] = val[2] + val[2] = t + } + + table[0] = constructHuffmanCode(1, val[0]) + table[1] = constructHuffmanCode(2, val[1]) + table[2] = constructHuffmanCode(1, val[0]) + table[3] = constructHuffmanCode(3, val[2]) + table[4] = constructHuffmanCode(1, val[0]) + table[5] = constructHuffmanCode(2, val[1]) + table[6] = constructHuffmanCode(1, val[0]) + table[7] = constructHuffmanCode(3, val[3]) + table_size = 8 + } + + for table_size != goal_size { + copy(table[table_size:], table[:uint(table_size)]) + table_size <<= 1 + } + + return goal_size +} |