blob: a1153c859a471ef2ac124a69ed53dd9ba8c8e84b [file] [log] [blame]
/* Copyright 2013 Google Inc. All Rights Reserved.
Distributed under MIT license.
See file LICENSE for detail or copy at
// Models the histograms of literals, commands and distance codes.
#include <cstring>
#include <limits>
#include <vector>
#include "./context.h"
#include "./command.h"
#include "./fast_log.h"
#include "./prefix.h"
#include "./types.h"
namespace brotli {
struct BlockSplit;
// A simple container for histograms of data in blocks.
template<int kDataSize>
struct Histogram {
Histogram(void) {
void Clear(void) {
memset(data_, 0, sizeof(data_));
total_count_ = 0;
bit_cost_ = std::numeric_limits<double>::infinity();
void Add(size_t val) {
void Remove(size_t val) {
template<typename DataType>
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 (size_t i = 0; i < kDataSize; ++i) {
data_[i] += v.data_[i];
uint32_t data_[kDataSize];
size_t total_count_;
double bit_cost_;
// Literal histogram.
typedef Histogram<256> HistogramLiteral;
// Prefix histograms.
typedef Histogram<kNumCommandPrefixes> HistogramCommand;
typedef Histogram<kNumDistancePrefixes> HistogramDistance;
typedef Histogram<kNumBlockLenPrefixes> 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 size_t kLiteralContextBits = 6;
static const size_t 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<ContextType>& context_modes,
std::vector<HistogramLiteral>* literal_histograms,
std::vector<HistogramCommand>* insert_and_copy_histograms,
std::vector<HistogramDistance>* copy_dist_histograms);
} // namespace brotli