зеркало из https://github.com/mozilla/gecko-dev.git
122 строки
4.0 KiB
C
122 строки
4.0 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/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_HUFFMAN_MAX_CODE_LENGTH 15
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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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#if ((defined(BROTLI_TARGET_ARMV7) || defined(BROTLI_TARGET_ARMV8_32)) && \
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BROTLI_GNUC_HAS_ATTRIBUTE(aligned, 2, 7, 0))
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#define BROTLI_HUFFMAN_CODE_FAST_LOAD
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#endif
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#if !defined(BROTLI_HUFFMAN_CODE_FAST_LOAD)
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/* Do not create this struct directly - use the ConstructHuffmanCode
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* constructor below! */
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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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static BROTLI_INLINE HuffmanCode ConstructHuffmanCode(const uint8_t bits,
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const uint16_t value) {
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HuffmanCode h;
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h.bits = bits;
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h.value = value;
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return h;
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}
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/* Please use the following macros to optimize HuffmanCode accesses in hot
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* paths.
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*
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* For example, assuming |table| contains a HuffmanCode pointer:
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*
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* BROTLI_HC_MARK_TABLE_FOR_FAST_LOAD(table);
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* BROTLI_HC_ADJUST_TABLE_INDEX(table, index_into_table);
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* *bits = BROTLI_HC_GET_BITS(table);
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* *value = BROTLI_HC_GET_VALUE(table);
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* BROTLI_HC_ADJUST_TABLE_INDEX(table, offset);
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* *bits2 = BROTLI_HC_GET_BITS(table);
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* *value2 = BROTLI_HC_GET_VALUE(table);
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*
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*/
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#define BROTLI_HC_MARK_TABLE_FOR_FAST_LOAD(H)
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#define BROTLI_HC_ADJUST_TABLE_INDEX(H, V) H += (V)
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/* These must be given a HuffmanCode pointer! */
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#define BROTLI_HC_FAST_LOAD_BITS(H) (H->bits)
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#define BROTLI_HC_FAST_LOAD_VALUE(H) (H->value)
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#else /* BROTLI_HUFFMAN_CODE_FAST_LOAD */
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typedef BROTLI_ALIGNED(4) uint32_t HuffmanCode;
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static BROTLI_INLINE HuffmanCode ConstructHuffmanCode(const uint8_t bits,
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const uint16_t value) {
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return (HuffmanCode) ((value & 0xFFFF) << 16) | (bits & 0xFF);
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}
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#define BROTLI_HC_MARK_TABLE_FOR_FAST_LOAD(H) uint32_t __fastload_##H = (*H)
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#define BROTLI_HC_ADJUST_TABLE_INDEX(H, V) H += (V); __fastload_##H = (*H)
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/* These must be given a HuffmanCode pointer! */
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#define BROTLI_HC_FAST_LOAD_BITS(H) ((__fastload_##H) & 0xFF)
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#define BROTLI_HC_FAST_LOAD_VALUE(H) ((__fastload_##H) >> 16)
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#endif /* BROTLI_HUFFMAN_CODE_FAST_LOAD */
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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);
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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,
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2 means 3 symbols, 3 means 4 symbols with lengths [2, 2, 2, 2],
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4 means 4 symbols with 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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/* alphabet_size_limit is needed due to simple codes, since
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log2(alphabet_size_max) could be greater than log2(alphabet_size_limit). */
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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_max;
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uint16_t alphabet_size_limit;
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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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