1 files changed, 61 insertions, 4 deletions

diff --git a/media/audio/simple_sources.h b/media/audio/simple_sources.h
index 992aba5..1da4d4f 100644
--- a/media/audio/simple_sources.h
+++ b/media/audio/simple_sources.h
@@ -5,18 +5,18 @@
 #ifndef MEDIA_AUDIO_SIMPLE_SOURCES_H_
 #define MEDIA_AUDIO_SIMPLE_SOURCES_H_
 
+#include <list>
+
+#include "base/lock.h"
 #include "media/audio/audio_output.h"
 
-// An audio source that produces a pure sinusoidal tone. Each platform needs
-// a slightly different implementation because it needs to handle the native
-// audio buffer format.
+// An audio source that produces a pure sinusoidal tone.
 class SineWaveAudioSource : public AudioOutputStream::AudioSourceCallback {
  public:
   enum Format {
     FORMAT_8BIT_LINEAR_PCM,
     FORMAT_16BIT_LINEAR_PCM,
   };
-
   // |channels| is the number of audio channels, |freq| is the frequency in
   // hertz and it has to be less than half of the sampling frequency
   // |sample_freq| or else you will get aliasing.
@@ -37,4 +37,61 @@ class SineWaveAudioSource : public AudioOutputStream::AudioSourceCallback {
   double sample_freq_;
 };
 
+// Defines an interface for pushing audio output. In contrast, the interfaces
+// defined by AudioSourceCallback are pull model only.
+class PushAudioOutput {
+ public:
+  virtual ~PushAudioOutput(){}
+
+  // Write audio data to the audio device. It will be played eventually.
+  // Returns false on failure.
+  virtual bool Write(const void* data, size_t len) = 0;
+
+  // Returns the number of bytes that have been buffered but not yet given
+  // to the audio device.
+  virtual size_t UnProcessedBytes() = 0;
+};
+
+// A fairly basic class to connect a push model provider PushAudioOutput to
+// a pull model provider AudioSourceCallback. Fundamentally it manages a series
+// of audio buffers and is unaware of the actual audio format.
+class PushSource : public AudioOutputStream::AudioSourceCallback,
+                   public PushAudioOutput {
+ public:
+  // Construct the audio source. Pass the same |packet_size| specified in the
+  // AudioOutputStream::Open() here.
+  explicit PushSource(size_t packet_size);
+  virtual ~PushSource();
+
+  // Write one buffer. The ideal size is |packet_size| but smaller sizes are
+  // accepted. Bigger sizes are an error. Returns false on error.
+  virtual bool Write(const void* data, size_t len);
+
+  // Return the total number of bytes not given to the audio device yet.
+  virtual size_t UnProcessedBytes();
+
+  // Implementation of AudioSourceCallback.
+  virtual size_t OnMoreData(AudioOutputStream* stream,
+                            void* dest, size_t max_size);
+  virtual void OnClose(AudioOutputStream* stream);
+  virtual void OnError(AudioOutputStream* stream, int code);
+
+ private:
+  // Defines the unit of playback. We own the memory pointed by |buffer|. 
+  struct Packet {
+    char* buffer;
+    size_t size;
+  };
+
+  // Free acquired resources.
+  void CleanUp();
+
+  const size_t packet_size_;
+  typedef std::list<Packet> PacketList; 
+  PacketList packets_;
+  size_t buffered_bytes_;
+  // Serialize access to packets_ and buffered_bytes_ using this lock.
+  Lock lock_;
+};
+
 #endif  // MEDIA_AUDIO_SIMPLE_SOURCES_H_