MJPEG acceleration for video capture using VAAPI, the GPU and IPC part

content/common/gpu/media/gpu_jpeg_decode_accelerator.h

+// Copyright 2015 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_COMMON_GPU_MEDIA_GPU_JPEG_DECODE_ACCELERATOR_H_
+#define CONTENT_COMMON_GPU_MEDIA_GPU_JPEG_DECODE_ACCELERATOR_H_
+
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "base/synchronization/waitable_event.h"
+#include "base/threading/non_thread_safe.h"
+#include "ipc/ipc_listener.h"
+#include "ipc/ipc_sender.h"
+#include "media/video/jpeg_decode_accelerator.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+}
+
+namespace content {
+class GpuChannel;
+
+class GpuJpegDecodeAccelerator
+    : public IPC::Sender,
+      public base::NonThreadSafe,
+      public base::SupportsWeakPtr<GpuJpegDecodeAccelerator> {
+ public:
+  // |channel| must outlive this object.
+  GpuJpegDecodeAccelerator(
+      GpuChannel* channel,
+      const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner);
+  ~GpuJpegDecodeAccelerator() override;
+
+  void AddClient(int32 route_id, IPC::Message* reply_msg);
+
+  void NotifyDecodeStatus(int32 route_id,
+                          int32_t bitstream_buffer_id,
+                          media::JpegDecodeAccelerator::Error error);
+
+  // Function to delegate sending to actual sender.
+  bool Send(IPC::Message* message) override;
+
+ private:
+  class Client;
+  class MessageFilter;
+
+  void ClientRemoved();
+
+  // The lifetime of objects of this class is managed by a GpuChannel. The
+  // GpuChannels destroy all the GpuJpegDecodeAccelerator that they own when

[palmer, 2015/06/11 23:28:28]

This comment feels a bit strange to me; as declared, the code seems to be saying
that GpuJpegDecodeAccelerator has-a GpuChannel* (to me, has-a means "owns a"),
but the comment says the opposite. Can you please clarify?

[wuchengli, 2015/06/12 02:29:41]

The comment is right. GpuChannel owns GpuJpegDecodeAccelerator. In my
understanding, a pointer does not indicate the ownership, scoped_ptr does.
Shared ownership is discouraged in the style guide. That leaves us using
a plain pointer.

[kcwu, 2015/06/12 12:22:00]

Yes, as wuchengli said, GpuChannel owns GpuJpegDecodeAccelerator.

+  // they are destroyed. So a raw pointer is safe.
+  GpuChannel* channel_;
+
+  // The message filter to run JpegDecodeAccelerator::Decode on IO thread.
+  scoped_refptr<MessageFilter> filter_;
+
+  // GPU child task runner.
+  scoped_refptr<base::SingleThreadTaskRunner> child_task_runner_;
+
+  // GPU IO task runner.
+  scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
+
+  // Number of clients added to |filter_|.
+  int client_number_;
+
+  DISALLOW_IMPLICIT_CONSTRUCTORS(GpuJpegDecodeAccelerator);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_COMMON_GPU_MEDIA_GPU_JPEG_DECODE_ACCELERATOR_H_