Add VP9 raw bits reader

media/filters/vp9_raw_bits_reader.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/filters/vp9_raw_bits_reader.h"
+
+#include <limits.h>
+
+#include "base/logging.h"
+#include "media/base/bit_reader.h"
+
+namespace media {
+
+Vp9RawBitsReader::Vp9RawBitsReader() : valid_(true) {}
+
+Vp9RawBitsReader::~Vp9RawBitsReader() {}
+
+void Vp9RawBitsReader::Initialize(const uint8_t* data, size_t size) {
+  DCHECK(data);
+  reader_.reset(new BitReader(data, size));
+  valid_ = true;
+}
+
+int Vp9RawBitsReader::ReadBit() {
+  DCHECK(reader_);
+  int value = 0;
+  valid_ = valid_ && reader_->ReadBits(1, &value);
+  return value;
+}
+
+int Vp9RawBitsReader::ReadLiteral(int bits) {
+  DCHECK(reader_);
+  int value = 0;
+  DCHECK_LT(static_cast<size_t>(bits), sizeof(value) * 8);
+  valid_ = valid_ && reader_->ReadBits(bits, &value);
+  return value;
+}
+
+int Vp9RawBitsReader::ReadSignedLiteral(int bits) {
+  int value = ReadLiteral(bits);
+  return ReadBit() ? -value : value;
+}
+
+size_t Vp9RawBitsReader::GetBytesRead() const {
+  DCHECK(reader_);
+  return (reader_->bits_read() + 7) / 8;
+}
+
+}  // namespace media