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107 lines
2.9 KiB
107 lines
2.9 KiB
// Copyright 2013 Google Inc. All Rights Reserved. |
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// |
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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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// |
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// http://www.apache.org/licenses/LICENSE-2.0 |
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// |
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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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// 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 <stdint.h> |
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#include <string.h> |
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#include <vector> |
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#include <utility> |
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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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namespace brotli { |
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class 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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} |
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void Add(int val) { |
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++data_[val]; |
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++total_count_; |
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} |
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void Remove(int 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 (int 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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double EntropyBitCost() const { |
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double retval = total_count_ * FastLog2(total_count_); |
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for (int i = 0; i < kDataSize; ++i) { |
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retval -= data_[i] * FastLog2(data_[i]); |
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} |
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return retval; |
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} |
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int data_[kDataSize]; |
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int 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 int kLiteralContextBits = 6; |
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static const int 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<int>& 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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