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1bf1b0a598
In quality 1, use static Huffman codes for distance and command histograms with <= 128 symbols and dynamic Huffman codes with static code length codes for the other histograms.
176 lines
6.8 KiB
C++
176 lines
6.8 KiB
C++
/* Copyright 2014 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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// Functions to convert brotli-related data structures into the
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// brotli bit stream. The functions here operate under
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// assumption that there is enough space in the storage, i.e., there are
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// no out-of-range checks anywhere.
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//
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// These functions do bit addressing into a byte array. The byte array
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// is called "storage" and the index to the bit is called storage_ix
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// in function arguments.
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#ifndef BROTLI_ENC_BROTLI_BIT_STREAM_H_
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#define BROTLI_ENC_BROTLI_BIT_STREAM_H_
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#include <vector>
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#include "./metablock.h"
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#include "./types.h"
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namespace brotli {
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// All Store functions here will use a storage_ix, which is always the bit
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// position for the current storage.
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// Stores a number between 0 and 255.
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void StoreVarLenUint8(size_t n, size_t* storage_ix, uint8_t* storage);
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// Stores the compressed meta-block header.
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// REQUIRES: length > 0
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// REQUIRES: length <= (1 << 24)
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void StoreCompressedMetaBlockHeader(bool final_block,
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size_t length,
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size_t* storage_ix,
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uint8_t* storage);
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// Stores the uncompressed meta-block header.
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// REQUIRES: length > 0
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// REQUIRES: length <= (1 << 24)
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void StoreUncompressedMetaBlockHeader(size_t length,
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size_t* storage_ix,
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uint8_t* storage);
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// Stores a context map where the histogram type is always the block type.
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void StoreTrivialContextMap(size_t num_types,
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size_t context_bits,
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size_t* storage_ix,
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uint8_t* storage);
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void StoreHuffmanTreeOfHuffmanTreeToBitMask(
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const int num_codes,
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const uint8_t *code_length_bitdepth,
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size_t *storage_ix,
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uint8_t *storage);
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void StoreHuffmanTree(const uint8_t* depths, size_t num,
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size_t *storage_ix, uint8_t *storage);
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// Builds a Huffman tree from histogram[0:length] into depth[0:length] and
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// bits[0:length] and stores the encoded tree to the bit stream.
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void BuildAndStoreHuffmanTree(const uint32_t *histogram,
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const size_t length,
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uint8_t* depth,
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uint16_t* bits,
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size_t* storage_ix,
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uint8_t* storage);
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void BuildAndStoreHuffmanTreeFast(const uint32_t *histogram,
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const size_t histogram_total,
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const size_t max_bits,
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uint8_t* depth,
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uint16_t* bits,
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size_t* storage_ix,
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uint8_t* storage);
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// Encodes the given context map to the bit stream. The number of different
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// histogram ids is given by num_clusters.
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void EncodeContextMap(const std::vector<uint32_t>& context_map,
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size_t num_clusters,
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size_t* storage_ix, uint8_t* storage);
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// Data structure that stores everything that is needed to encode each block
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// switch command.
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struct BlockSplitCode {
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std::vector<uint32_t> type_code;
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std::vector<uint32_t> length_prefix;
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std::vector<uint32_t> length_nextra;
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std::vector<uint32_t> length_extra;
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std::vector<uint8_t> type_depths;
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std::vector<uint16_t> type_bits;
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std::vector<uint8_t> length_depths;
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std::vector<uint16_t> length_bits;
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};
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// Builds a BlockSplitCode data structure from the block split given by the
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// vector of block types and block lengths and stores it to the bit stream.
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void BuildAndStoreBlockSplitCode(const std::vector<uint8_t>& types,
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const std::vector<uint32_t>& lengths,
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const size_t num_types,
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BlockSplitCode* code,
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size_t* storage_ix,
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uint8_t* storage);
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// Stores the block switch command with index block_ix to the bit stream.
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void StoreBlockSwitch(const BlockSplitCode& code,
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const size_t block_ix,
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size_t* storage_ix,
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uint8_t* storage);
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// REQUIRES: length > 0
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// REQUIRES: length <= (1 << 24)
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void StoreMetaBlock(const uint8_t* input,
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size_t start_pos,
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size_t length,
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size_t mask,
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uint8_t prev_byte,
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uint8_t prev_byte2,
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bool final_block,
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uint32_t num_direct_distance_codes,
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uint32_t distance_postfix_bits,
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ContextType literal_context_mode,
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const brotli::Command *commands,
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size_t n_commands,
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const MetaBlockSplit& mb,
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size_t *storage_ix,
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uint8_t *storage);
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// Stores the meta-block without doing any block splitting, just collects
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// one histogram per block category and uses that for entropy coding.
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// REQUIRES: length > 0
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// REQUIRES: length <= (1 << 24)
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void StoreMetaBlockTrivial(const uint8_t* input,
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size_t start_pos,
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size_t length,
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size_t mask,
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bool is_last,
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const brotli::Command *commands,
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size_t n_commands,
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size_t *storage_ix,
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uint8_t *storage);
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// Same as above, but uses static prefix codes for histograms with a only a few
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// symbols, and uses static code length prefix codes for all other histograms.
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// REQUIRES: length > 0
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// REQUIRES: length <= (1 << 24)
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void StoreMetaBlockFast(const uint8_t* input,
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size_t start_pos,
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size_t length,
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size_t mask,
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bool is_last,
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const brotli::Command *commands,
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size_t n_commands,
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size_t *storage_ix,
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uint8_t *storage);
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// This is for storing uncompressed blocks (simple raw storage of
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// bytes-as-bytes).
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// REQUIRES: length > 0
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// REQUIRES: length <= (1 << 24)
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void StoreUncompressedMetaBlock(bool final_block,
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const uint8_t* input,
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size_t position, size_t mask,
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size_t len,
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size_t* storage_ix,
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uint8_t* storage);
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// Stores an empty metadata meta-block and syncs to a byte boundary.
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void StoreSyncMetaBlock(size_t* storage_ix, uint8_t* storage);
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} // namespace brotli
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#endif // BROTLI_ENC_BROTLI_BIT_STREAM_H_
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