Split MoveReadPosition into Forward and Backward versions.

webrtc/common_audio/audio_ring_buffer.h

 /*
  *  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.
  */
 #ifndef WEBRTC_COMMON_AUDIO_AUDIO_RING_BUFFER_H_
 #define WEBRTC_COMMON_AUDIO_AUDIO_RING_BUFFER_H_
 
 #include <stddef.h>
 #include <vector>
 
 struct RingBuffer;
 
 namespace webrtc {
 
 // A ring buffer tailored for float deinterleaved audio. Any operation that
 // cannot be performed as requested will cause a crash (e.g. insufficient data
 // in the buffer to fulfill a read request.)
 class AudioRingBuffer final {
  public:
   // Specify the number of channels and maximum number of frames the buffer will
   // contain.
   AudioRingBuffer(size_t channels, size_t max_frames);
   ~AudioRingBuffer();
 
-  // Copy |data| to the buffer and advance the write pointer. |channels| must
+  // Copies |data| to the buffer and advances the write pointer. |channels| must
   // be the same as at creation time.
   void Write(const float* const* data, size_t channels, size_t frames);
 
-  // Copy from the buffer to |data| and advance the read pointer. |channels|
+  // Copies from the buffer to |data| and advances the read pointer. |channels|
   // must be the same as at creation time.
   void Read(float* const* data, size_t channels, size_t frames);
 
   size_t ReadFramesAvailable() const;
   size_t WriteFramesAvailable() const;
 
-  // Positive values advance the read pointer and negative values withdraw
-  // the read pointer (i.e. flush and stuff the buffer respectively.)
-  void MoveReadPosition(int frames);
+  // Moves the read position. The forward version advances the read pointer
+  // towards the write pointer and the backward verison withdraws the read
+  // pointer away from the write pointer (i.e. flushing and stuffing the buffer
+  // respectively.)
+  void MoveReadPositionForward(size_t frames);
+  void MoveReadPositionBackward(size_t frames);
 
  private:
   // We don't use a ScopedVector because it doesn't support a specialized
   // deleter (like scoped_ptr for instance.)
   std::vector<RingBuffer*> buffers_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_COMMON_AUDIO_AUDIO_RING_BUFFER_H_