/* Copyright 2013 Google Inc. All Rights Reserved.
Distributed under MIT license.
See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
*/
// Build per-context histograms of literals, commands and distance codes.
#include "./histogram.h"
#include <cmath>
#include "./block_splitter.h"
#include "./command.h"
#include "./context.h"
#include "./prefix.h"
namespace brotli {
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 start_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) {
size_t pos = start_pos;
BlockSplitIterator literal_it(literal_split);
BlockSplitIterator insert_and_copy_it(insert_and_copy_split);
BlockSplitIterator dist_it(dist_split);
for (size_t i = 0; i < num_commands; ++i) {
const Command &cmd = cmds[i];
insert_and_copy_it.Next();
(*insert_and_copy_histograms)[insert_and_copy_it.type_].Add(
cmd.cmd_prefix_);
for (size_t j = cmd.insert_len_; j != 0; --j) {
literal_it.Next();
size_t context = (literal_it.type_ << kLiteralContextBits) +
Context(prev_byte, prev_byte2, context_modes[literal_it.type_]);
(*literal_histograms)[context].Add(ringbuffer[pos & mask]);
prev_byte2 = prev_byte;
prev_byte = ringbuffer[pos & mask];
++pos;
}
pos += cmd.copy_len_;
if (cmd.copy_len_ > 0) {
prev_byte2 = ringbuffer[(pos - 2) & mask];
prev_byte = ringbuffer[(pos - 1) & mask];
if (cmd.cmd_prefix_ >= 128) {
dist_it.Next();
size_t context = (dist_it.type_ << kDistanceContextBits) +
cmd.DistanceContext();
(*copy_dist_histograms)[context].Add(cmd.dist_prefix_);
}
}
}
}
} // namespace brotli
