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69 lines
2.3 KiB
C
69 lines
2.3 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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#ifndef BROTLI_DEC_HUFFMAN_H_
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#define BROTLI_DEC_HUFFMAN_H_
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#include "../common/types.h"
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#include "./port.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_HUFFMAN_MAX_CODE_LENGTH 15
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/* Maximum possible Huffman table size for an alphabet size of (index * 32),
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* max code length 15 and root table bits 8. */
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static const uint16_t kMaxHuffmanTableSize[] = {
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256, 402, 436, 468, 500, 534, 566, 598, 630, 662, 694, 726, 758, 790, 822,
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854, 886, 920, 952, 984, 1016, 1048, 1080};
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/* BROTLI_NUM_BLOCK_LEN_SYMBOLS == 26 */
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#define BROTLI_HUFFMAN_MAX_SIZE_26 396
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/* BROTLI_MAX_BLOCK_TYPE_SYMBOLS == 258 */
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#define BROTLI_HUFFMAN_MAX_SIZE_258 632
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/* BROTLI_MAX_CONTEXT_MAP_SYMBOLS == 272 */
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#define BROTLI_HUFFMAN_MAX_SIZE_272 646
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#define BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH 5
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typedef struct {
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uint8_t bits; /* number of bits used for this symbol */
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uint16_t value; /* symbol value or table offset */
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} HuffmanCode;
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/* Builds Huffman lookup table assuming code lengths are in symbol order. */
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BROTLI_INTERNAL void BrotliBuildCodeLengthsHuffmanTable(HuffmanCode* root_table,
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const uint8_t* const code_lengths, uint16_t* count);
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/* Builds Huffman lookup table assuming code lengths are in symbol order. */
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/* Returns size of resulting table. */
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BROTLI_INTERNAL uint32_t BrotliBuildHuffmanTable(HuffmanCode* root_table,
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int root_bits, const uint16_t* const symbol_lists, uint16_t* count_arg);
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/* Builds a simple Huffman table. The num_symbols parameter is to be */
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/* interpreted as follows: 0 means 1 symbol, 1 means 2 symbols, 2 means 3 */
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/* symbols, 3 means 4 symbols with lengths 2,2,2,2, 4 means 4 symbols with */
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/* lengths 1,2,3,3. */
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BROTLI_INTERNAL uint32_t BrotliBuildSimpleHuffmanTable(HuffmanCode* table,
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int root_bits, uint16_t* symbols, uint32_t num_symbols);
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/* Contains a collection of Huffman trees with the same alphabet size. */
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typedef struct {
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HuffmanCode** htrees;
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HuffmanCode* codes;
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uint16_t alphabet_size;
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uint16_t num_htrees;
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} HuffmanTreeGroup;
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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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#endif /* BROTLI_DEC_HUFFMAN_H_ */
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