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// 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.
//
// Build per-context histograms of literals, commands and distance codes.
#include "./histogram.h"
#include <stdint.h>
#include <cmath>
#include "./block_splitter.h"
#include "./command.h"
#include "./context.h"
#include "./prefix.h"
namespace brotli {
void BuildHistograms(
const std::vector<Command>& cmds,
const BlockSplit& literal_split,
const BlockSplit& insert_and_copy_split,
const BlockSplit& dist_split,
const uint8_t* ringbuffer,
size_t pos,
size_t mask,
const std::vector<int>& context_modes,
std::vector<HistogramLiteral>* literal_histograms,
std::vector<HistogramCommand>* insert_and_copy_histograms,
std::vector<HistogramDistance>* copy_dist_histograms) {
BlockSplitIterator literal_it(literal_split);
BlockSplitIterator insert_and_copy_it(insert_and_copy_split);
BlockSplitIterator dist_it(dist_split);
for (int i = 0; i < cmds.size(); ++i) {
const Command &cmd = cmds[i];
insert_and_copy_it.Next();
(*insert_and_copy_histograms)[insert_and_copy_it.type_].Add(
cmd.command_prefix_);
for (int j = 0; j < cmd.insert_length_; ++j) {
literal_it.Next();
uint8_t prev_byte = pos > 0 ? ringbuffer[(pos - 1) & mask] : 0;
uint8_t prev_byte2 = pos > 1 ? ringbuffer[(pos - 2) & mask] : 0;
int context = (literal_it.type_ << kLiteralContextBits) +
Context(prev_byte, prev_byte2, context_modes[literal_it.type_]);
(*literal_histograms)[context].Add(ringbuffer[pos & mask]);
++pos;
}
pos += cmd.copy_length_;
if (cmd.copy_length_ > 0 && cmd.distance_prefix_ != 0xffff) {
dist_it.Next();
int context = (dist_it.type_ << kDistanceContextBits) +
((cmd.copy_length_code_ > 4) ? 3 : cmd.copy_length_code_ - 2);
(*copy_dist_histograms)[context].Add(cmd.distance_prefix_);
}
}
}
void BuildLiteralHistogramsForBlockType(
const std::vector<Command>& cmds,
const BlockSplit& literal_split,
const uint8_t* ringbuffer,
size_t pos,
size_t mask,
int block_type,
int context_mode,
std::vector<HistogramLiteral>* histograms) {
BlockSplitIterator literal_it(literal_split);
for (int i = 0; i < cmds.size(); ++i) {
const Command &cmd = cmds[i];
for (int j = 0; j < cmd.insert_length_; ++j) {
literal_it.Next();
if (literal_it.type_ == block_type) {
uint8_t prev_byte = pos > 0 ? ringbuffer[(pos - 1) & mask] : 0;
uint8_t prev_byte2 = pos > 1 ? ringbuffer[(pos - 2) & mask] : 0;
int context = Context(prev_byte, prev_byte2, context_mode);
(*histograms)[context].Add(ringbuffer[pos & mask]);
}
++pos;
}
pos += cmd.copy_length_;
}
}
} // namespace brotli
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