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82 lines
2.8 KiB
C
82 lines
2.8 KiB
C
/* Copyright 2013 Google Inc. All Rights Reserved.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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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 "./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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/* For current format this constant equals to kNumInsertAndCopyCodes */
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#define BROTLI_HUFFMAN_MAX_CODE_LENGTHS_SIZE 704
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/* Maximum possible Huffman table size for an alphabet size of 704, max code
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* length 15 and root table bits 8. */
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#define BROTLI_HUFFMAN_MAX_TABLE_SIZE 1080
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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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void BrotliBuildCodeLengthsHuffmanTable(HuffmanCode* root_table,
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const uint8_t* const code_lengths,
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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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int 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_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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int BrotliBuildSimpleHuffmanTable(HuffmanCode* table,
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int root_bits,
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uint16_t *symbols,
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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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int16_t alphabet_size;
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int16_t num_htrees;
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} HuffmanTreeGroup;
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void BrotliHuffmanTreeGroupInit(HuffmanTreeGroup* group,
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int alphabet_size, int ntrees);
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void BrotliHuffmanTreeGroupRelease(HuffmanTreeGroup* group);
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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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