[PPAPI] Implement media stream video track API

ppapi/shared_impl/media_stream_frame_buffer.h

+// Copyright (c) 2014 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 PPAPI_SHARED_IMPL_MEDIA_STREAM_FRAME_BUFFER_H_
+#define PPAPI_SHARED_IMPL_MEDIA_STREAM_FRAME_BUFFER_H_
+
+#include <deque>
+#include <vector>
+
+#include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/shared_memory.h"
+#include "ppapi/shared_impl/media_stream_frame.h"
+#include "ppapi/shared_impl/ppapi_shared_export.h"
+
+namespace ppapi {
+
+class PPAPI_SHARED_EXPORT MediaStreamFrameBuffer {
+ public:
+  class Delegate {
+    public:
+      // It is called when a new frame is enqueued.
+     virtual void OnNewFrameEnqueued();
+  };

[dmichael (off chromium), 2014/01/09 21:06:47]

It might be simpler to just use a base::Closure for this?

[Peng, 2014/01/10 19:14:30]

I tried. It does not simplify code too much. :(

HostBase and ResourceBase will implement the Delegate and create
MediaStreamFrameBuffer. But those two classes will not implement
OnNewFrameEnqueued(), their subclasses may implement it.So use Closure is not
very convenient.

+
+  explicit MediaStreamFrameBuffer(Delegate* delegate);

[dmichael (off chromium), 2014/01/09 21:06:47]

(If you keep the Delegate class, comment about ownership here...  looks like
it's unowned, and must outlive the MediaStreamFrameBuffer object).

[Peng, 2014/01/10 19:14:30]

Done.

+
+  ~MediaStreamFrameBuffer();
+
+  int32_t number_of_frames() const { return number_of_frames_; }
+
+  int32_t frame_size() const { return frame_size_; }
+
+  // Initializes shared memory for frames transmission.
+  bool SetFrames(int32_t number_of_frames,
+                 int32_t frame_size,
+                 scoped_ptr<base::SharedMemory> shm,
+                 bool enqueue_all_frames);
+
+  // Dequeues a frame from |frame_queue_|.
+  int32_t DequeueFrame();
+
+  // Puts a frame into |frame_queue_|.
+  void EnqueueFrame(int32_t index);
+
+  // Gets a frame address for the given index.
+  MediaStreamFrame* GetFramePointer(int32_t index);
+
+ private:
+  Delegate* delegate_;
+  // A queue of incoming frame indexes.

[dmichael (off chromium), 2014/01/09 21:06:47]

Can you elaborate more? It's not obvious what "incoming" means...  incoming from
the peer?

[Peng, 2014/01/10 19:14:30]

I added a class level document. Done

+  // For the input side, they are empty frames which will be filled with data
+  // and sent to the output side.
+  // For the output side, they are received frames waiting for consuming.
+  std::deque<int32_t> frame_queue_;
+
+  // A vector of frame pointers. It is used for index to pointer converting.
+  std::vector<MediaStreamFrame*> frames_;
+
+  // The frame size in bytes.
+  int32_t frame_size_;
+
+  // The number of frames in the shared memory.
+  int32_t number_of_frames_;
+
+  // A memory block shared between renderer and plugin processes.
+  scoped_ptr<base::SharedMemory> shm_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaStreamFrameBuffer);
+};
+
+}  // namespace ppapi
+
+#endif  // PPAPI_SHAERD_IMPL_MEDIA_STREAM_FRAME_BUFFER_H_