Split MoveReadPosition into Forward and Backward versions.

webrtc/common_audio/audio_ring_buffer.cc

 /*
  *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #include "webrtc/common_audio/audio_ring_buffer.h"
 
 #include "webrtc/base/checks.h"
+#include "webrtc/base/safe_conversions.h"
 #include "webrtc/common_audio/ring_buffer.h"
 
 // This is a simple multi-channel wrapper over the ring_buffer.h C interface.
 
 namespace webrtc {
 
 AudioRingBuffer::AudioRingBuffer(size_t channels, size_t max_frames) {
+  buffers_.reserve(channels);
   for (size_t i = 0; i < channels; ++i)
     buffers_.push_back(WebRtc_CreateBuffer(max_frames, sizeof(float)));
 }
 
 AudioRingBuffer::~AudioRingBuffer() {
   for (auto buf : buffers_)
     WebRtc_FreeBuffer(buf);
 }
 
 void AudioRingBuffer::Write(const float* const* data, size_t channels,
                             size_t frames) {
   DCHECK_EQ(buffers_.size(), channels);
   for (size_t i = 0; i < channels; ++i) {
-    size_t written = WebRtc_WriteBuffer(buffers_[i], data[i], frames);
+    const size_t written = WebRtc_WriteBuffer(buffers_[i], data[i], frames);
     CHECK_EQ(written, frames);
   }
 }
 
 void AudioRingBuffer::Read(float* const* data, size_t channels, size_t frames) {
   DCHECK_EQ(buffers_.size(), channels);
   for (size_t i = 0; i < channels; ++i) {
-    size_t read = WebRtc_ReadBuffer(buffers_[i], nullptr, data[i], frames);
+    const size_t read =
+        WebRtc_ReadBuffer(buffers_[i], nullptr, data[i], frames);
     CHECK_EQ(read, frames);
   }
 }
 
 size_t AudioRingBuffer::ReadFramesAvailable() const {
   // All buffers have the same amount available.
   return WebRtc_available_read(buffers_[0]);
 }
 
 size_t AudioRingBuffer::WriteFramesAvailable() const {
   // All buffers have the same amount available.
   return WebRtc_available_write(buffers_[0]);
 }
 
-void AudioRingBuffer::MoveReadPosition(int frames) {
+void AudioRingBuffer::MoveReadPositionForward(size_t frames) {
   for (auto buf : buffers_) {
-    int moved = WebRtc_MoveReadPtr(buf, frames);
+    const size_t moved = WebRtc_MoveReadPtr(buf, frames);
     CHECK_EQ(moved, frames);
   }
 }
+
+void AudioRingBuffer::MoveReadPositionBackward(size_t frames) {
+  for (auto buf : buffers_) {
+    const size_t moved = rtc::checked_cast<size_t>(

[Andrew MacDonald, 2015/07/24 19:06:39]

We already check this value below, so a checked cast isn't needed.

+        -WebRtc_MoveReadPtr(buf, -static_cast<int>(frames)));
+    CHECK_EQ(moved, frames);
+  }
+}
 
 }  // namespace webrtc