[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 {
+
+// This class is used by both read side and write side of a MediaStreamTrack to
+// maintain a queue of frames for reading or writing.
+//
+// An example:
+//  1. The writer calls the writer's |frame_buffer_.Dequeue()| to get a free
+//     frame.
+//  2. The writer fills data into the frame.
+//  3. The writer sends the frame index to the reader via an IPC message.
+//  4. The reader receives the frame index and calls the reader's
+//     |frame_buffer.Enqueue()| to put the frame into the read's queue.
+//  5. The reader calls reader's |frame_buffer_.Dequeue()| to get a received
+//     frame.
+//  6. When the frame from the step 5 is consumed, the reader sends the frame
+//     index back to writer via an IPC message.
+//  7. The writer receives the frame index and puts it back to the writer's free
+//     frame queue by calling the writer's |frame_buffer_.Enqueue()|.
+//  8. Go back to step 1.
+class PPAPI_SHARED_EXPORT MediaStreamFrameBuffer {
+ public:
+  class PPAPI_SHARED_EXPORT Delegate {
+   public:
+    virtual ~Delegate();
+    // It is called when a new frame is enqueued.
+    virtual void OnNewFrameEnqueued();
+  };
+
+  // MediaStreamFrameBuffer doesn't own |delegate|, the caller should keep
+  // it alive during the MediaStreamFrameBuffer's lifecycle.
+  explicit MediaStreamFrameBuffer(Delegate* delegate);
+
+  ~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 the frame address for the given frame index.
+  MediaStreamFrame* GetFramePointer(int32_t index);
+
+ private:
+  Delegate* delegate_;
+
+  // A queue of frame indexes.
+  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 process and plugin process.
+  scoped_ptr<base::SharedMemory> shm_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaStreamFrameBuffer);
+};
+
+}  // namespace ppapi
+
+#endif  // PPAPI_SHAERD_IMPL_MEDIA_STREAM_FRAME_BUFFER_H_