[PPAPI] Implement media stream video track API

ppapi/proxy/media_stream_video_track_resource.cc

+// 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.
+
+#include "ppapi/proxy/media_stream_video_track_resource.h"
+
+#include "ppapi/proxy/video_frame_resource.h"
+#include "ppapi/shared_impl/media_stream_frame.h"
+#include "ppapi/shared_impl/var.h"
+#include "ppapi/thunk/enter.h"
+
+namespace ppapi {
+namespace proxy {
+
+MediaStreamVideoTrackResource::MediaStreamVideoTrackResource(
+    Connection connection,
+    PP_Instance instance,
+    int pending_renderer_id,
+    const std::string& id)
+    : MediaStreamTrackResourceBase(
+        connection, instance, pending_renderer_id, id),
+      get_frame_output_(NULL) {
+}
+
+MediaStreamVideoTrackResource::~MediaStreamVideoTrackResource() {
+}
+
+thunk::PPB_MediaStreamVideoTrack_API*
+MediaStreamVideoTrackResource::AsPPB_MediaStreamVideoTrack_API() {
+  return this;
+}
+
+PP_Var MediaStreamVideoTrackResource::GetId() {
+  return StringVar::StringToPPVar(id());
+}
+
+PP_Bool MediaStreamVideoTrackResource::HasEnded() {
+  return PP_FromBool(has_ended());
+}
+
+int32_t MediaStreamVideoTrackResource::Configure(uint32_t max_buffered_frames) {
+  // TODO(penghuang): redesign and implement Configure() to support format,
+  // size, etc.
+  return PP_ERROR_NOTSUPPORTED;
+}
+
+int32_t MediaStreamVideoTrackResource::GetFrame(
+    PP_Resource* frame,
+    scoped_refptr<ppapi::TrackedCallback> callback) {
+  if (has_ended())
+    return PP_ERROR_FAILED;
+
+  if (TrackedCallback::IsPending(get_frame_callback_))
+    return PP_ERROR_INPROGRESS;
+
+  *frame = GetVideoFrame();
+  if (*frame)
+    return PP_OK;
+
+  get_frame_output_ = frame;
+  get_frame_callback_ = callback;
+  return PP_OK_COMPLETIONPENDING;
+}
+
+int32_t MediaStreamVideoTrackResource::RecycleFrame(PP_Resource frame) {
+  thunk::EnterResourceNoLock<thunk::PPB_VideoFrame_API>enter_frame(frame, true);

[yzshen1, 2014/01/10 21:05:17]

one space before enter_frame, please.

[Peng, 2014/01/10 22:46:58]

Done.

+  if (enter_frame.failed())
+    return PP_ERROR_BADRESOURCE;
+

[yzshen1, 2014/01/10 21:05:17]

In another file, I mentioned that this class should maintain a list of
unrecycled frames, in order to invalidate unrecycled frames on destruction.

This method can also use that unrecycled frames list: we need to check whether
|frame| is actually a frame returned by this object. Otherwise, the index may
point to a buffer slot that is not owned by this object. And we mess up things.

What do you think?

[Peng, 2014/01/10 22:46:58]

It is a good idea. Done

+  VideoFrameResource* frame_resource =
+      static_cast<VideoFrameResource*>(enter_frame.resource());

[bbudge, 2014/01/10 22:57:06]

It's unusual to cast to the underlying type when we have an API layer. Could we
add the methods you need to PPB_VideoFrame_API?

I searched Chrome with this query:
EnterResourceNoLock static_cast ".resource()"

[Peng, 2014/01/13 19:10:15]

As yzshen's suggestion, I use a FrameMap here to convert a PP_Resource to
FrameResource pointer.

I think it resolve this issue. Done

+  if (frame_resource->index() < 0)
+    return PP_ERROR_BADRESOURCE;
+
+  HostEnqueueFrame(frame_resource->index());
+  frame_resource->invalidate();
+  return PP_OK;
+}
+
+void MediaStreamVideoTrackResource::Close() {
+  if (TrackedCallback::IsPending(get_frame_callback_)) {
+    *get_frame_output_ = 0;
+    get_frame_callback_->PostRun(PP_ERROR_FAILED);

[yzshen1, 2014/01/10 21:05:17]

It is more common to use PostAbort() in this case.

[Peng, 2014/01/10 22:46:58]

Done.

+    get_frame_callback_ = NULL;
+    get_frame_output_ = 0;
+  }
+  MediaStreamTrackResourceBase::CloseInternal();
+}
+
+void MediaStreamVideoTrackResource::OnNewFrameEnqueued() {
+  if (TrackedCallback::IsPending(get_frame_callback_)) {
+    *get_frame_output_ = GetVideoFrame();
+    get_frame_callback_->PostRun(PP_OK);
+    get_frame_callback_ = NULL;
+    get_frame_output_ = 0;
+  }
+}
+
+PP_Resource MediaStreamVideoTrackResource::GetVideoFrame() {
+  int32_t index = frame_buffer()->DequeueFrame();
+  if (index < 0)
+    return 0;
+  MediaStreamFrame::Video* frame =
+      &(frame_buffer()->GetFramePointer(index)->video);
+  return (new VideoFrameResource(pp_instance(), index, frame))->GetReference();
+}
+
+}  // namespace proxy
+}  // namespace ppapi