// Copyright 2013 Google Inc. All Rights Reserved. // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. // // Models the histograms of literals, commands and distance codes. #ifndef BROTLI_ENC_HISTOGRAM_H_ #define BROTLI_ENC_HISTOGRAM_H_ #include #include #include #include #include "./command.h" #include "./fast_log.h" #include "./prefix.h" namespace brotli { class BlockSplit; // A simple container for histograms of data in blocks. template struct Histogram { Histogram() { Clear(); } void Clear() { memset(data_, 0, sizeof(data_)); total_count_ = 0; } void Add(int val) { ++data_[val]; ++total_count_; } void Remove(int val) { --data_[val]; --total_count_; } template void Add(const DataType *p, size_t n) { total_count_ += n; n += 1; while(--n) ++data_[*p++]; } void AddHistogram(const Histogram& v) { total_count_ += v.total_count_; for (int i = 0; i < kDataSize; ++i) { data_[i] += v.data_[i]; } } double EntropyBitCost() const { double retval = total_count_ * FastLog2(total_count_); for (int i = 0; i < kDataSize; ++i) { retval -= data_[i] * FastLog2(data_[i]); } return retval; } int data_[kDataSize]; int total_count_; double bit_cost_; }; // Literal histogram. typedef Histogram<256> HistogramLiteral; // Prefix histograms. typedef Histogram HistogramCommand; typedef Histogram HistogramDistance; typedef Histogram HistogramBlockLength; // Context map histogram, 256 Huffman tree indexes + 16 run length codes. typedef Histogram<272> HistogramContextMap; // Block type histogram, 256 block types + 2 special symbols. typedef Histogram<258> HistogramBlockType; static const int kLiteralContextBits = 6; static const int kDistanceContextBits = 2; void BuildHistograms( const Command* cmds, const size_t num_commands, const BlockSplit& literal_split, const BlockSplit& insert_and_copy_split, const BlockSplit& dist_split, const uint8_t* ringbuffer, size_t pos, size_t mask, uint8_t prev_byte, uint8_t prev_byte2, const std::vector& context_modes, std::vector* literal_histograms, std::vector* insert_and_copy_histograms, std::vector* copy_dist_histograms); } // namespace brotli #endif // BROTLI_ENC_HISTOGRAM_H_