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95 lines
2.4 KiB
C++
95 lines
2.4 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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// Models the histograms of literals, commands and distance codes.
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#ifndef BROTLI_ENC_HISTOGRAM_H_
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#define BROTLI_ENC_HISTOGRAM_H_
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#include <cstring>
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#include <limits>
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#include <vector>
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#include "./context.h"
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#include "./command.h"
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#include "./fast_log.h"
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#include "./prefix.h"
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#include "./types.h"
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namespace brotli {
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struct BlockSplit;
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// A simple container for histograms of data in blocks.
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template<int kDataSize>
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struct Histogram {
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Histogram() {
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Clear();
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}
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void Clear() {
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memset(data_, 0, sizeof(data_));
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total_count_ = 0;
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bit_cost_ = std::numeric_limits<double>::infinity();
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}
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void Add(size_t val) {
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++data_[val];
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++total_count_;
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}
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void Remove(size_t val) {
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--data_[val];
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--total_count_;
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}
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template<typename DataType>
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void Add(const DataType *p, size_t n) {
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total_count_ += n;
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n += 1;
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while(--n) ++data_[*p++];
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}
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void AddHistogram(const Histogram& v) {
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total_count_ += v.total_count_;
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for (size_t i = 0; i < kDataSize; ++i) {
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data_[i] += v.data_[i];
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}
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}
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uint32_t data_[kDataSize];
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size_t total_count_;
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double bit_cost_;
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};
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// Literal histogram.
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typedef Histogram<256> HistogramLiteral;
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// Prefix histograms.
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typedef Histogram<kNumCommandPrefixes> HistogramCommand;
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typedef Histogram<kNumDistancePrefixes> HistogramDistance;
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typedef Histogram<kNumBlockLenPrefixes> HistogramBlockLength;
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// Context map histogram, 256 Huffman tree indexes + 16 run length codes.
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typedef Histogram<272> HistogramContextMap;
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// Block type histogram, 256 block types + 2 special symbols.
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typedef Histogram<258> HistogramBlockType;
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static const size_t kLiteralContextBits = 6;
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static const size_t kDistanceContextBits = 2;
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void BuildHistograms(
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const Command* cmds,
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const size_t num_commands,
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const BlockSplit& literal_split,
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const BlockSplit& insert_and_copy_split,
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const BlockSplit& dist_split,
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const uint8_t* ringbuffer,
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size_t pos,
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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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const std::vector<ContextType>& context_modes,
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std::vector<HistogramLiteral>* literal_histograms,
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std::vector<HistogramCommand>* insert_and_copy_histograms,
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std::vector<HistogramDistance>* copy_dist_histograms);
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} // namespace brotli
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#endif // BROTLI_ENC_HISTOGRAM_H_
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