Introduce AudioBus to replace std::vector<float*>.

media/base/audio_bus.h

+// Copyright (c) 2012 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.
+
+#ifndef MEDIA_BASE_AUDIO_BUS_H_
+#define MEDIA_BASE_AUDIO_BUS_H_
+
+#include <vector>
+
+#include "base/memory/aligned_memory.h"
+#include "base/memory/scoped_ptr.h"
+#include "media/base/media_export.h"
+
+namespace media {
+class AudioParameters;
+
+// Scoped container for "busing" audio channel data around.  Each channel is
+// stored in planar format and guaranteed to have a 16-byte alignment.  AudioBus
+// objects can be created normally or via wrapping.  Normally, AudioBus will
+// dice up a contiguous memory block for channel data.  When wrapped, AudioBus
+// instead routes requests for channel data to the wrapped object.
+class MEDIA_EXPORT AudioBus {
+ public:
+  // Creates a new AudioBus and allocates |channels| of length |frames|.  Uses
+  // channels() and frames_per_buffer() if given an AudioParameters object.
+  static scoped_ptr<AudioBus> Create(int channels, int frames);
+  static scoped_ptr<AudioBus> Create(const AudioParameters& params);
+
+  // Creates a new AudioBus from an existing channel vector.  Does not transfer
+  // ownership of |channel_data| to AudioBus; i.e., |channel_data| must outlive
+  // the returned AudioBus.  Each channel pointer must be 16-byte aligned.
+  static scoped_ptr<AudioBus> WrapVector(
+      int frames, const std::vector<float*>& channel_data);
+
+  // Returns a raw pointer to internal channel data.  Useful for copying state
+  // between two AudioBus objects created with the same parameters.  data_size()
+  // is in bytes.  Can not be used with an AudioBus constructed via wrapping.
+  void* data();
+  int data_size() const;
+
+  // Returns a raw pointer to the requested channel.  Pointer is guaranteed to
+  // have a 16-byte alignment.
+  float* channel(int channel) { return channel_data_[channel]; }
+  const float* channel(int channel) const { return channel_data_[channel]; }
+
+  int channels() const { return channel_data_.size(); }
+  int frames() const { return frames_; }
+
+  // Helper method for zeroing out all channels of audio data.
+  void Zero();
+  void ZeroFrames(int frames);
+
+ private:
+  friend class scoped_ptr<AudioBus>;
+  ~AudioBus();
+
+  AudioBus(int channels, int frames);
+  AudioBus(int frames, const std::vector<float*>& channel_data);
+
+  // Contiguous block of channel memory.
+  scoped_ptr_malloc<float, base::ScopedPtrAlignedFree> data_;
+  int data_size_;
+
+  std::vector<float*> channel_data_;
+  int frames_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioBus);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_AUDIO_BUS_H_