chromium/media/parsers/vp9_bool_decoder.cc

// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifdef UNSAFE_BUFFERS_BUILD
// TODO(crbug.com/40285824): Remove this and convert code to safer constructs.
#pragma allow_unsafe_buffers
#endif

#include "media/parsers/vp9_bool_decoder.h"

#include <algorithm>
#include <memory>

#include "base/logging.h"
#include "media/base/bit_reader.h"

namespace media {

namespace {

// This is an optimization lookup table for the loop in spec 9.2.2.
//     while BoolRange <= 128:
//       read 1 bit
//       BoolRange *= 2
// This table indicates how many iterations to run for a given BoolRange. So
// the loop could be reduced to
//     read (kCountToShiftTo128[BoolRange]) bits
const int kCountToShiftTo128[256] = …;
}  // namespace

Vp9BoolDecoder::Vp9BoolDecoder() = default;

Vp9BoolDecoder::~Vp9BoolDecoder() = default;

// 9.2.1 Initialization process for Boolean decoder
bool Vp9BoolDecoder::Initialize(const uint8_t* data, size_t size) { … }

// Fill at least |count_to_fill_| bits and prefill remain bits of |bool_value_|
// if data is enough.
bool Vp9BoolDecoder::Fill() { … }

// 9.2.2 Boolean decoding process
bool Vp9BoolDecoder::ReadBool(int prob) { … }

// 9.2.4 Parsing process for read_literal
uint8_t Vp9BoolDecoder::ReadLiteral(int bits) { … }

bool Vp9BoolDecoder::ConsumePaddingBits() { … }

}  // namespace media