Use multiple shared memory buffers cyclically for audio capture.

content/browser/renderer_host/media/audio_input_sync_writer.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 CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_INPUT_SYNC_WRITER_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_INPUT_SYNC_WRITER_H_
 
 #include "base/file_descriptor_posix.h"
 #include "base/process.h"
 #include "base/sync_socket.h"
 #include "media/audio/audio_input_controller.h"
 
 namespace base {
 class SharedMemory;
 }
 
 namespace content {
 // A AudioInputController::SyncWriter implementation using SyncSocket. This
 // is used by AudioInputController to provide a low latency data source for
 // transmitting audio packets between the browser process and the renderer
 // process.
 class AudioInputSyncWriter : public media::AudioInputController::SyncWriter {
  public:
-  explicit AudioInputSyncWriter(base::SharedMemory* shared_memory);
+  explicit AudioInputSyncWriter(base::SharedMemory* shared_memory,
+                                int shared_memory_segment_count);
 
   virtual ~AudioInputSyncWriter();
 
   // media::AudioOutputController::SyncWriter implementation.
   virtual void UpdateRecordedBytes(uint32 bytes) OVERRIDE;
   virtual uint32 Write(const void* data, uint32 size, double volume) OVERRIDE;
   virtual void Close() OVERRIDE;
 
   bool Init();
   bool PrepareForeignSocketHandle(base::ProcessHandle process_handle,
 #if defined(OS_WIN)
                                   base::SyncSocket::Handle* foreign_handle);
 #else
                                   base::FileDescriptor* foreign_handle);
 #endif
 
  private:
   base::SharedMemory* shared_memory_;
+  uint32 shared_memory_segment_size_;
+  uint32 shared_memory_segment_count_;
+  uint32 current_segment_id_;
 
   // Socket for transmitting audio data.
   scoped_ptr<base::CancelableSyncSocket> socket_;
 
   // Socket to be used by the renderer. The reference is released after
   // PrepareForeignSocketHandle() is called and ran successfully.
   scoped_ptr<base::CancelableSyncSocket> foreign_socket_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(AudioInputSyncWriter);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_INPUT_SYNC_WRITER_H_