339 lines
12 KiB
C
339 lines
12 KiB
C
/* Copyright 2013 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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/* Utilities for building Huffman decoding tables. */
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#include "huffman.h"
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#include <string.h> /* memcpy, memset */
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#include "../common/constants.h"
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#include "../common/platform.h"
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#include <brotli/types.h>
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#if defined(__cplusplus) || defined(c_plusplus)
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extern "C" {
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#endif
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#define BROTLI_REVERSE_BITS_MAX 8
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#if defined(BROTLI_RBIT)
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#define BROTLI_REVERSE_BITS_BASE \
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((sizeof(brotli_reg_t) << 3) - BROTLI_REVERSE_BITS_MAX)
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#else
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#define BROTLI_REVERSE_BITS_BASE 0
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static uint8_t kReverseBits[1 << BROTLI_REVERSE_BITS_MAX] = {
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0x00, 0x80, 0x40, 0xC0, 0x20, 0xA0, 0x60, 0xE0,
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0x10, 0x90, 0x50, 0xD0, 0x30, 0xB0, 0x70, 0xF0,
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0x08, 0x88, 0x48, 0xC8, 0x28, 0xA8, 0x68, 0xE8,
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0x18, 0x98, 0x58, 0xD8, 0x38, 0xB8, 0x78, 0xF8,
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0x04, 0x84, 0x44, 0xC4, 0x24, 0xA4, 0x64, 0xE4,
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0x14, 0x94, 0x54, 0xD4, 0x34, 0xB4, 0x74, 0xF4,
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0x0C, 0x8C, 0x4C, 0xCC, 0x2C, 0xAC, 0x6C, 0xEC,
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0x1C, 0x9C, 0x5C, 0xDC, 0x3C, 0xBC, 0x7C, 0xFC,
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0x02, 0x82, 0x42, 0xC2, 0x22, 0xA2, 0x62, 0xE2,
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0x12, 0x92, 0x52, 0xD2, 0x32, 0xB2, 0x72, 0xF2,
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0x0A, 0x8A, 0x4A, 0xCA, 0x2A, 0xAA, 0x6A, 0xEA,
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0x1A, 0x9A, 0x5A, 0xDA, 0x3A, 0xBA, 0x7A, 0xFA,
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0x06, 0x86, 0x46, 0xC6, 0x26, 0xA6, 0x66, 0xE6,
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0x16, 0x96, 0x56, 0xD6, 0x36, 0xB6, 0x76, 0xF6,
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0x0E, 0x8E, 0x4E, 0xCE, 0x2E, 0xAE, 0x6E, 0xEE,
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0x1E, 0x9E, 0x5E, 0xDE, 0x3E, 0xBE, 0x7E, 0xFE,
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0x01, 0x81, 0x41, 0xC1, 0x21, 0xA1, 0x61, 0xE1,
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0x11, 0x91, 0x51, 0xD1, 0x31, 0xB1, 0x71, 0xF1,
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0x09, 0x89, 0x49, 0xC9, 0x29, 0xA9, 0x69, 0xE9,
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0x19, 0x99, 0x59, 0xD9, 0x39, 0xB9, 0x79, 0xF9,
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0x05, 0x85, 0x45, 0xC5, 0x25, 0xA5, 0x65, 0xE5,
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0x15, 0x95, 0x55, 0xD5, 0x35, 0xB5, 0x75, 0xF5,
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0x0D, 0x8D, 0x4D, 0xCD, 0x2D, 0xAD, 0x6D, 0xED,
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0x1D, 0x9D, 0x5D, 0xDD, 0x3D, 0xBD, 0x7D, 0xFD,
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0x03, 0x83, 0x43, 0xC3, 0x23, 0xA3, 0x63, 0xE3,
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0x13, 0x93, 0x53, 0xD3, 0x33, 0xB3, 0x73, 0xF3,
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0x0B, 0x8B, 0x4B, 0xCB, 0x2B, 0xAB, 0x6B, 0xEB,
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0x1B, 0x9B, 0x5B, 0xDB, 0x3B, 0xBB, 0x7B, 0xFB,
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0x07, 0x87, 0x47, 0xC7, 0x27, 0xA7, 0x67, 0xE7,
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0x17, 0x97, 0x57, 0xD7, 0x37, 0xB7, 0x77, 0xF7,
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0x0F, 0x8F, 0x4F, 0xCF, 0x2F, 0xAF, 0x6F, 0xEF,
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0x1F, 0x9F, 0x5F, 0xDF, 0x3F, 0xBF, 0x7F, 0xFF
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};
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#endif /* BROTLI_RBIT */
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#define BROTLI_REVERSE_BITS_LOWEST \
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((brotli_reg_t)1 << (BROTLI_REVERSE_BITS_MAX - 1 + BROTLI_REVERSE_BITS_BASE))
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/* Returns reverse(num >> BROTLI_REVERSE_BITS_BASE, BROTLI_REVERSE_BITS_MAX),
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where reverse(value, len) is the bit-wise reversal of the len least
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significant bits of value. */
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static BROTLI_INLINE brotli_reg_t BrotliReverseBits(brotli_reg_t num) {
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#if defined(BROTLI_RBIT)
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return BROTLI_RBIT(num);
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#else
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return kReverseBits[num];
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#endif
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}
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/* Stores code in table[0], table[step], table[2*step], ..., table[end] */
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/* Assumes that end is an integer multiple of step */
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static BROTLI_INLINE void ReplicateValue(HuffmanCode* table,
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int step, int end,
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HuffmanCode code) {
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do {
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end -= step;
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table[end] = code;
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} while (end > 0);
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}
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/* Returns the table width of the next 2nd level table. |count| is the histogram
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of bit lengths for the remaining symbols, |len| is the code length of the
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next processed symbol. */
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static BROTLI_INLINE int NextTableBitSize(const uint16_t* const count,
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int len, int root_bits) {
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int left = 1 << (len - root_bits);
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while (len < BROTLI_HUFFMAN_MAX_CODE_LENGTH) {
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left -= count[len];
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if (left <= 0) break;
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++len;
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left <<= 1;
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}
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return len - root_bits;
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}
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void BrotliBuildCodeLengthsHuffmanTable(HuffmanCode* table,
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const uint8_t* const code_lengths,
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uint16_t* count) {
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HuffmanCode code; /* current table entry */
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int symbol; /* symbol index in original or sorted table */
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brotli_reg_t key; /* prefix code */
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brotli_reg_t key_step; /* prefix code addend */
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int step; /* step size to replicate values in current table */
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int table_size; /* size of current table */
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int sorted[BROTLI_CODE_LENGTH_CODES]; /* symbols sorted by code length */
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/* offsets in sorted table for each length */
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int offset[BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH + 1];
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int bits;
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int bits_count;
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BROTLI_DCHECK(BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH <=
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BROTLI_REVERSE_BITS_MAX);
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/* Generate offsets into sorted symbol table by code length. */
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symbol = -1;
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bits = 1;
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BROTLI_REPEAT(BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH, {
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symbol += count[bits];
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offset[bits] = symbol;
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bits++;
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});
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/* Symbols with code length 0 are placed after all other symbols. */
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offset[0] = BROTLI_CODE_LENGTH_CODES - 1;
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/* Sort symbols by length, by symbol order within each length. */
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symbol = BROTLI_CODE_LENGTH_CODES;
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do {
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BROTLI_REPEAT(6, {
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symbol--;
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sorted[offset[code_lengths[symbol]]--] = symbol;
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});
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} while (symbol != 0);
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table_size = 1 << BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH;
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/* Special case: all symbols but one have 0 code length. */
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if (offset[0] == 0) {
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code = ConstructHuffmanCode(0, (uint16_t)sorted[0]);
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for (key = 0; key < (brotli_reg_t)table_size; ++key) {
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table[key] = code;
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}
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return;
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}
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/* Fill in table. */
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key = 0;
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key_step = BROTLI_REVERSE_BITS_LOWEST;
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symbol = 0;
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bits = 1;
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step = 2;
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do {
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for (bits_count = count[bits]; bits_count != 0; --bits_count) {
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code = ConstructHuffmanCode((uint8_t)bits, (uint16_t)sorted[symbol++]);
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ReplicateValue(&table[BrotliReverseBits(key)], step, table_size, code);
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key += key_step;
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}
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step <<= 1;
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key_step >>= 1;
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} while (++bits <= BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH);
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}
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uint32_t BrotliBuildHuffmanTable(HuffmanCode* root_table,
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int root_bits,
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const uint16_t* const symbol_lists,
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uint16_t* count) {
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HuffmanCode code; /* current table entry */
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HuffmanCode* table; /* next available space in table */
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int len; /* current code length */
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int symbol; /* symbol index in original or sorted table */
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brotli_reg_t key; /* prefix code */
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brotli_reg_t key_step; /* prefix code addend */
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brotli_reg_t sub_key; /* 2nd level table prefix code */
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brotli_reg_t sub_key_step; /* 2nd level table prefix code addend */
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int step; /* step size to replicate values in current table */
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int table_bits; /* key length of current table */
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int table_size; /* size of current table */
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int total_size; /* sum of root table size and 2nd level table sizes */
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int max_length = -1;
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int bits;
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int bits_count;
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BROTLI_DCHECK(root_bits <= BROTLI_REVERSE_BITS_MAX);
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BROTLI_DCHECK(BROTLI_HUFFMAN_MAX_CODE_LENGTH - root_bits <=
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BROTLI_REVERSE_BITS_MAX);
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while (symbol_lists[max_length] == 0xFFFF) max_length--;
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max_length += BROTLI_HUFFMAN_MAX_CODE_LENGTH + 1;
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table = root_table;
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table_bits = root_bits;
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table_size = 1 << table_bits;
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total_size = table_size;
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/* Fill in the root table. Reduce the table size to if possible,
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and create the repetitions by memcpy. */
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if (table_bits > max_length) {
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table_bits = max_length;
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table_size = 1 << table_bits;
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}
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key = 0;
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key_step = BROTLI_REVERSE_BITS_LOWEST;
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bits = 1;
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step = 2;
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do {
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symbol = bits - (BROTLI_HUFFMAN_MAX_CODE_LENGTH + 1);
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for (bits_count = count[bits]; bits_count != 0; --bits_count) {
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symbol = symbol_lists[symbol];
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code = ConstructHuffmanCode((uint8_t)bits, (uint16_t)symbol);
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ReplicateValue(&table[BrotliReverseBits(key)], step, table_size, code);
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key += key_step;
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}
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step <<= 1;
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key_step >>= 1;
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} while (++bits <= table_bits);
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/* If root_bits != table_bits then replicate to fill the remaining slots. */
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while (total_size != table_size) {
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memcpy(&table[table_size], &table[0],
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(size_t)table_size * sizeof(table[0]));
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table_size <<= 1;
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}
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/* Fill in 2nd level tables and add pointers to root table. */
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key_step = BROTLI_REVERSE_BITS_LOWEST >> (root_bits - 1);
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sub_key = (BROTLI_REVERSE_BITS_LOWEST << 1);
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sub_key_step = BROTLI_REVERSE_BITS_LOWEST;
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for (len = root_bits + 1, step = 2; len <= max_length; ++len) {
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symbol = len - (BROTLI_HUFFMAN_MAX_CODE_LENGTH + 1);
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for (; count[len] != 0; --count[len]) {
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if (sub_key == (BROTLI_REVERSE_BITS_LOWEST << 1U)) {
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table += table_size;
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table_bits = NextTableBitSize(count, len, root_bits);
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table_size = 1 << table_bits;
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total_size += table_size;
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sub_key = BrotliReverseBits(key);
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key += key_step;
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root_table[sub_key] = ConstructHuffmanCode(
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(uint8_t)(table_bits + root_bits),
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(uint16_t)(((size_t)(table - root_table)) - sub_key));
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sub_key = 0;
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}
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symbol = symbol_lists[symbol];
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code = ConstructHuffmanCode((uint8_t)(len - root_bits), (uint16_t)symbol);
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ReplicateValue(
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&table[BrotliReverseBits(sub_key)], step, table_size, code);
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sub_key += sub_key_step;
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}
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step <<= 1;
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sub_key_step >>= 1;
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}
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return (uint32_t)total_size;
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}
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uint32_t BrotliBuildSimpleHuffmanTable(HuffmanCode* table,
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int root_bits,
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uint16_t* val,
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uint32_t num_symbols) {
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uint32_t table_size = 1;
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const uint32_t goal_size = 1U << root_bits;
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switch (num_symbols) {
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case 0:
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table[0] = ConstructHuffmanCode(0, val[0]);
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break;
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case 1:
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if (val[1] > val[0]) {
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table[0] = ConstructHuffmanCode(1, val[0]);
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table[1] = ConstructHuffmanCode(1, val[1]);
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} else {
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table[0] = ConstructHuffmanCode(1, val[1]);
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table[1] = ConstructHuffmanCode(1, val[0]);
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}
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table_size = 2;
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break;
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case 2:
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table[0] = ConstructHuffmanCode(1, val[0]);
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table[2] = ConstructHuffmanCode(1, val[0]);
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if (val[2] > val[1]) {
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table[1] = ConstructHuffmanCode(2, val[1]);
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table[3] = ConstructHuffmanCode(2, val[2]);
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} else {
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table[1] = ConstructHuffmanCode(2, val[2]);
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table[3] = ConstructHuffmanCode(2, val[1]);
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}
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table_size = 4;
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break;
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case 3: {
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int i, k;
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for (i = 0; i < 3; ++i) {
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for (k = i + 1; k < 4; ++k) {
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if (val[k] < val[i]) {
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uint16_t t = val[k];
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val[k] = val[i];
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val[i] = t;
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}
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}
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}
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table[0] = ConstructHuffmanCode(2, val[0]);
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table[2] = ConstructHuffmanCode(2, val[1]);
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table[1] = ConstructHuffmanCode(2, val[2]);
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table[3] = ConstructHuffmanCode(2, val[3]);
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table_size = 4;
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break;
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}
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case 4: {
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if (val[3] < val[2]) {
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uint16_t t = val[3];
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val[3] = val[2];
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val[2] = t;
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}
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table[0] = ConstructHuffmanCode(1, val[0]);
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table[1] = ConstructHuffmanCode(2, val[1]);
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table[2] = ConstructHuffmanCode(1, val[0]);
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table[3] = ConstructHuffmanCode(3, val[2]);
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table[4] = ConstructHuffmanCode(1, val[0]);
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table[5] = ConstructHuffmanCode(2, val[1]);
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table[6] = ConstructHuffmanCode(1, val[0]);
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table[7] = ConstructHuffmanCode(3, val[3]);
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table_size = 8;
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break;
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}
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}
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while (table_size != goal_size) {
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memcpy(&table[table_size], &table[0],
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(size_t)table_size * sizeof(table[0]));
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table_size <<= 1;
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}
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return goal_size;
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}
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#if defined(__cplusplus) || defined(c_plusplus)
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} /* extern "C" */
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#endif
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