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Diffstat (limited to 'modules/brotli/dec/huffman.c')
| -rw-r--r-- | modules/brotli/dec/huffman.c | 356 |
1 files changed, 356 insertions, 0 deletions
diff --git a/modules/brotli/dec/huffman.c b/modules/brotli/dec/huffman.c new file mode 100644 index 000000000..3775ffe7e --- /dev/null +++ b/modules/brotli/dec/huffman.c @@ -0,0 +1,356 @@ +/* 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. */ + +#include "./huffman.h" + +#include <string.h> /* memcpy, memset */ + +#include "./port.h" +#include "./types.h" + +#if defined(__cplusplus) || defined(c_plusplus) +extern "C" { +#endif + +#define BROTLI_REVERSE_BITS_MAX 8 + +#ifdef BROTLI_RBIT +#define BROTLI_REVERSE_BITS_BASE (32 - BROTLI_REVERSE_BITS_MAX) +#else +#define BROTLI_REVERSE_BITS_BASE 0 +static uint8_t kReverseBits[1 << BROTLI_REVERSE_BITS_MAX] = { + 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 +}; +#endif /* BROTLI_RBIT */ + +#define BROTLI_REVERSE_BITS_LOWEST \ + (1U << (BROTLI_REVERSE_BITS_MAX - 1 + BROTLI_REVERSE_BITS_BASE)) + +/* 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. */ +static BROTLI_INLINE uint32_t BrotliReverseBits(uint32_t num) { +#ifdef BROTLI_RBIT + return BROTLI_RBIT(num); +#else + return kReverseBits[num]; +#endif +} + +/* Stores code in table[0], table[step], table[2*step], ..., table[end] */ +/* Assumes that end is an integer multiple of step */ +static BROTLI_INLINE void ReplicateValue(HuffmanCode* table, + int step, int end, + HuffmanCode code) { + do { + end -= step; + table[end] = code; + } while (end > 0); +} + +/* 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 */ +static BROTLI_INLINE int NextTableBitSize(const uint16_t* const count, + int len, int root_bits) { + int left = 1 << (len - root_bits); + while (len < BROTLI_HUFFMAN_MAX_CODE_LENGTH) { + left -= count[len]; + if (left <= 0) break; + ++len; + left <<= 1; + } + return len - root_bits; +} + +void BrotliBuildCodeLengthsHuffmanTable(HuffmanCode* table, + const uint8_t* const code_lengths, + uint16_t* count) { + HuffmanCode code; /* current table entry */ + int symbol; /* symbol index in original or sorted table */ + uint32_t key; /* prefix code */ + uint32_t key_step; /* prefix code addend */ + int step; /* step size to replicate values in current table */ + int table_size; /* size of current table */ + int sorted[18]; /* symbols sorted by code length */ + /* offsets in sorted table for each length */ + int offset[BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH + 1]; + int bits; + int bits_count; + BROTLI_DCHECK(BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH <= + BROTLI_REVERSE_BITS_MAX); + + /* generate offsets into sorted symbol table by code length */ + symbol = -1; + bits = 1; + BROTLI_REPEAT(BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH, { + symbol += count[bits]; + offset[bits] = symbol; + bits++; + }); + /* Symbols with code length 0 are placed after all other symbols. */ + offset[0] = 17; + + /* sort symbols by length, by symbol order within each length */ + symbol = 18; + do { + BROTLI_REPEAT(6, { + symbol--; + sorted[offset[code_lengths[symbol]]--] = symbol; + }); + } while (symbol != 0); + + table_size = 1 << BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH; + + /* Special case: all symbols but one have 0 code length. */ + if (offset[0] == 0) { + code.bits = 0; + code.value = (uint16_t)sorted[0]; + for (key = 0; key < (uint32_t)table_size; ++key) { + table[key] = code; + } + return; + } + + /* fill in table */ + key = 0; + key_step = BROTLI_REVERSE_BITS_LOWEST; + symbol = 0; + bits = 1; + step = 2; + do { + code.bits = (uint8_t)bits; + for (bits_count = count[bits]; bits_count != 0; --bits_count) { + code.value = (uint16_t)sorted[symbol++]; + ReplicateValue(&table[BrotliReverseBits(key)], step, table_size, code); + key += key_step; + } + step <<= 1; + key_step >>= 1; + } while (++bits <= BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH); +} + +uint32_t BrotliBuildHuffmanTable(HuffmanCode* root_table, + int root_bits, + const uint16_t* const symbol_lists, + uint16_t* count) { + HuffmanCode code; /* current table entry */ + HuffmanCode* table; /* next available space in table */ + int len; /* current code length */ + int symbol; /* symbol index in original or sorted table */ + uint32_t key; /* prefix code */ + uint32_t key_step; /* prefix code addend */ + uint32_t sub_key; /* 2nd level table prefix code */ + uint32_t sub_key_step; /* 2nd level table prefix code addend */ + int step; /* step size to replicate values in current table */ + int table_bits; /* key length of current table */ + int table_size; /* size of current table */ + int total_size; /* sum of root table size and 2nd level table sizes */ + int max_length = -1; + int bits; + int bits_count; + + BROTLI_DCHECK(root_bits <= BROTLI_REVERSE_BITS_MAX); + BROTLI_DCHECK(BROTLI_HUFFMAN_MAX_CODE_LENGTH - root_bits <= + BROTLI_REVERSE_BITS_MAX); + + while (symbol_lists[max_length] == 0xFFFF) max_length--; + max_length += BROTLI_HUFFMAN_MAX_CODE_LENGTH + 1; + + table = root_table; + table_bits = root_bits; + table_size = 1 << table_bits; + total_size = table_size; + + /* fill in root table */ + /* let's reduce the table size to a smaller size if possible, and */ + /* create the repetitions by memcpy if possible in the coming loop */ + if (table_bits > max_length) { + table_bits = max_length; + table_size = 1 << table_bits; + } + key = 0; + key_step = BROTLI_REVERSE_BITS_LOWEST; + bits = 1; + step = 2; + do { + code.bits = (uint8_t)bits; + symbol = bits - (BROTLI_HUFFMAN_MAX_CODE_LENGTH + 1); + for (bits_count = count[bits]; bits_count != 0; --bits_count) { + symbol = symbol_lists[symbol]; + code.value = (uint16_t)symbol; + ReplicateValue(&table[BrotliReverseBits(key)], step, table_size, code); + key += key_step; + } + step <<= 1; + key_step >>= 1; + } while (++bits <= table_bits); + + /* if root_bits != table_bits we only created one fraction of the */ + /* table, and we need to replicate it now. */ + while (total_size != table_size) { + memcpy(&table[table_size], &table[0], + (size_t)table_size * sizeof(table[0])); + table_size <<= 1; + } + + /* fill in 2nd level tables and add pointers to root table */ + key_step = BROTLI_REVERSE_BITS_LOWEST >> (root_bits - 1); + sub_key = (BROTLI_REVERSE_BITS_LOWEST << 1); + sub_key_step = BROTLI_REVERSE_BITS_LOWEST; + for (len = root_bits + 1, step = 2; len <= max_length; ++len) { + symbol = len - (BROTLI_HUFFMAN_MAX_CODE_LENGTH + 1); + for (; count[len] != 0; --count[len]) { + if (sub_key == (BROTLI_REVERSE_BITS_LOWEST << 1U)) { + table += table_size; + table_bits = NextTableBitSize(count, len, root_bits); + table_size = 1 << table_bits; + total_size += table_size; + sub_key = BrotliReverseBits(key); + key += key_step; + root_table[sub_key].bits = (uint8_t)(table_bits + root_bits); + root_table[sub_key].value = + (uint16_t)(((size_t)(table - root_table)) - sub_key); + sub_key = 0; + } + code.bits = (uint8_t)(len - root_bits); + symbol = symbol_lists[symbol]; + code.value = (uint16_t)symbol; + ReplicateValue( + &table[BrotliReverseBits(sub_key)], step, table_size, code); + sub_key += sub_key_step; + } + step <<= 1; + sub_key_step >>= 1; + } + return (uint32_t)total_size; +} + +uint32_t BrotliBuildSimpleHuffmanTable(HuffmanCode* table, + int root_bits, + uint16_t* val, + uint32_t num_symbols) { + uint32_t table_size = 1; + const uint32_t goal_size = 1U << root_bits; + switch (num_symbols) { + case 0: + table[0].bits = 0; + table[0].value = val[0]; + break; + case 1: + table[0].bits = 1; + table[1].bits = 1; + if (val[1] > val[0]) { + table[0].value = val[0]; + table[1].value = val[1]; + } else { + table[0].value = val[1]; + table[1].value = val[0]; + } + table_size = 2; + break; + case 2: + table[0].bits = 1; + table[0].value = val[0]; + table[2].bits = 1; + table[2].value = val[0]; + if (val[2] > val[1]) { + table[1].value = val[1]; + table[3].value = val[2]; + } else { + table[1].value = val[2]; + table[3].value = val[1]; + } + table[1].bits = 2; + table[3].bits = 2; + table_size = 4; + break; + case 3: { + int i, k; + for (i = 0; i < 3; ++i) { + for (k = i + 1; k < 4; ++k) { + if (val[k] < val[i]) { + uint16_t t = val[k]; + val[k] = val[i]; + val[i] = t; + } + } + } + for (i = 0; i < 4; ++i) { + table[i].bits = 2; + } + table[0].value = val[0]; + table[2].value = val[1]; + table[1].value = val[2]; + table[3].value = val[3]; + table_size = 4; + break; + } + case 4: { + int i; + if (val[3] < val[2]) { + uint16_t t = val[3]; + val[3] = val[2]; + val[2] = t; + } + for (i = 0; i < 7; ++i) { + table[i].value = val[0]; + table[i].bits = (uint8_t)(1 + (i & 1)); + } + table[1].value = val[1]; + table[3].value = val[2]; + table[5].value = val[1]; + table[7].value = val[3]; + table[3].bits = 3; + table[7].bits = 3; + table_size = 8; + break; + } + } + while (table_size != goal_size) { + memcpy(&table[table_size], &table[0], + (size_t)table_size * sizeof(table[0])); + table_size <<= 1; + } + return goal_size; +} + +#if defined(__cplusplus) || defined(c_plusplus) +} /* extern "C" */ +#endif |