Break tight coupling of VideoCaptureDeviceClient to renderer_host

content/browser/renderer_host/media/video_capture_buffer_pool.h

 // Copyright (c) 2013 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_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_BUFFER_POOL_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_BUFFER_POOL_H_
 
 #include <stddef.h>
 
 #include <map>
 
 #include "base/files/file.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/shared_memory.h"
 #include "base/process/process.h"
 #include "base/synchronization/lock.h"
 #include "build/build_config.h"
 #include "content/common/content_export.h"
 #include "media/base/video_capture_types.h"
 #include "media/base/video_frame.h"
 #include "ui/gfx/geometry/size.h"
 #include "ui/gfx/gpu_memory_buffer.h"
 
 namespace content {
 
+class VideoCaptureBufferPoolBufferHandle {
+ public:
+  virtual ~VideoCaptureBufferPoolBufferHandle() {}
+  virtual gfx::Size dimensions() const = 0;
+  virtual size_t mapped_size() const = 0;
+  virtual void* data(int plane) = 0;
+  virtual ClientBuffer AsClientBuffer(int plane) = 0;
+#if defined(OS_POSIX) && !defined(OS_MACOSX)
+  virtual base::FileDescriptor AsPlatformFile() = 0;
+#endif
+};
+
+class CONTENT_EXPORT ProducerVideoCaptureBufferPool
+    : public base::RefCountedThreadSafe<ProducerVideoCaptureBufferPool> {
+ public:
+  static constexpr int kInvalidId = -1;
+
+  // Try and obtain a BufferHandle for |buffer_id|.
+  virtual std::unique_ptr<VideoCaptureBufferPoolBufferHandle> GetBufferHandle(
+      int buffer_id) = 0;
+
+  // Reserve or allocate a buffer to support a packed frame of |dimensions| of
+  // pixel |format| and return its id. This will fail (returning kInvalidId) if
+  // the pool already is at its |count| limit of the number of allocations, and
+  // all allocated buffers are in use by the producer and/or consumers.
+  //
+  // If successful, the reserved buffer remains reserved (and writable by the
+  // producer) until ownership is transferred either to the consumer via
+  // HoldForConsumers(), or back to the pool with
+  // RelinquishProducerReservation().
+  //
+  // On occasion, this call will decide to free an old buffer to make room for a
+  // new allocation at a larger size. If so, the ID of the destroyed buffer is
+  // returned via |buffer_id_to_drop|.
+  virtual int ReserveForProducer(const gfx::Size& dimensions,
+                                 media::VideoPixelFormat format,
+                                 media::VideoPixelStorage storage,
+                                 int* buffer_id_to_drop) = 0;
+
+  // Indicate that a buffer held for the producer should be returned back to the
+  // pool without passing on to the consumer. This effectively is the opposite
+  // of ReserveForProducer().
+  virtual void RelinquishProducerReservation(int buffer_id) = 0;
+
+  // Attempt to reserve the same buffer that was relinquished in the last call
+  // to RelinquishProducerReservation(). If the buffer is not still being
+  // consumed, and has not yet been re-used since being consumed, and the
+  // specified |dimensions|, |format|, and |storage| agree with its last
+  // reservation, this will succeed. Otherwise, |kInvalidId| will be returned.
+  //
+  // A producer may assume the content of the buffer has been preserved and may
+  // also make modifications.
+  virtual int ResurrectLastForProducer(const gfx::Size& dimensions,
+                                       media::VideoPixelFormat format,
+                                       media::VideoPixelStorage storage) = 0;
+
+  // Returns a snapshot of the current number of buffers in-use divided by the
+  // maximum |count_|.
+  virtual double GetBufferPoolUtilization() = 0;
+
+ protected:
+  virtual ~ProducerVideoCaptureBufferPool() {}
+
+ private:
+  friend class base::RefCountedThreadSafe<ProducerVideoCaptureBufferPool>;
+};

[mcasas, 2016/09/09 22:28:01]

nit : add here a
DISALLOW_IMPLICIT_CONSTRUCTORS(ClassName);

actually, it should be added to all new base classes,
either that macro or DISALLOW_COPY_AND_ASSIGN,
whichever makes sense

[chfremer, 2016/09/12 18:31:22]

Done, but I have a question about it.
Why is this needed? Interface classed cannot be instantiated anyway, because
they consist of purely virtual methods only.

[chfremer, 2016/09/13 00:30:56]

Hmm. I tried both, but neither of the macros seems to be suitable here. Since
they remove the default constructor, derived classes can no longer instantiate,
and we get a compiler error.

+
 // A thread-safe class that does the bookkeeping and lifetime management for a
 // pool of pixel buffers cycled between an in-process producer (e.g. a
 // VideoCaptureDevice) and a set of out-of-process consumers. The pool is
 // intended to be orchestrated by a VideoCaptureDevice::Client, but is designed
 // to outlive the controller if necessary. The pixel buffers may be backed by a
 // SharedMemory, but this is not compulsory.
 //
 // Producers get a buffer by calling ReserveForProducer(), and may pass on their
 // ownership to the consumer by calling HoldForConsumers(), or drop the buffer
 // (without further processing) by calling RelinquishProducerReservation().
 // Consumers signal that they are done with the buffer by calling
 // RelinquishConsumerHold().
 //
 // Buffers are allocated on demand, but there will never be more than |count|
 // buffers in existence at any time. Buffers are identified by an int value
 // called |buffer_id|. -1 (kInvalidId) is never a valid ID, and is returned by
 // some methods to indicate failure. The active set of buffer ids may change
 // over the lifetime of the buffer pool, as existing buffers are freed and
 // reallocated at larger size. When reallocation occurs, new buffer IDs will
 // circulate.
 class CONTENT_EXPORT VideoCaptureBufferPool
-    : public base::RefCountedThreadSafe<VideoCaptureBufferPool> {
+    : public ProducerVideoCaptureBufferPool {
  public:
-  static const int kInvalidId;
-
-  // Abstraction of a pool's buffer data buffer and size for clients.
-  // TODO(emircan): See https://crbug.com/521059, refactor this class.
-  class BufferHandle {
-   public:
-    virtual ~BufferHandle() {}
-    virtual gfx::Size dimensions() const = 0;
-    virtual size_t mapped_size() const = 0;
-    virtual void* data(int plane) = 0;
-    virtual ClientBuffer AsClientBuffer(int plane) = 0;
-#if defined(OS_POSIX) && !defined(OS_MACOSX)
-    virtual base::FileDescriptor AsPlatformFile() = 0;
-#endif
-  };
+  using BufferHandle = VideoCaptureBufferPoolBufferHandle;
 
   explicit VideoCaptureBufferPool(int count);
 
   // One-time (per client/per-buffer) initialization to share a particular
   // buffer to a process. The shared handle is returned as |new_handle|.
   bool ShareToProcess(int buffer_id,
                       base::ProcessHandle process_handle,
                       base::SharedMemoryHandle* new_handle);
   bool ShareToProcess2(int buffer_id,
                        int plane,
                        base::ProcessHandle process_handle,
                        gfx::GpuMemoryBufferHandle* new_handle);
 
-  // Try and obtain a BufferHandle for |buffer_id|.
-  std::unique_ptr<BufferHandle> GetBufferHandle(int buffer_id);
-
-  // Reserve or allocate a buffer to support a packed frame of |dimensions| of
-  // pixel |format| and return its id. This will fail (returning kInvalidId) if
-  // the pool already is at its |count| limit of the number of allocations, and
-  // all allocated buffers are in use by the producer and/or consumers.
-  //
-  // If successful, the reserved buffer remains reserved (and writable by the
-  // producer) until ownership is transferred either to the consumer via
-  // HoldForConsumers(), or back to the pool with
-  // RelinquishProducerReservation().
-  //
-  // On occasion, this call will decide to free an old buffer to make room for a
-  // new allocation at a larger size. If so, the ID of the destroyed buffer is
-  // returned via |buffer_id_to_drop|.
+  // Implementation of ProducerVideoCaptureBufferPool interface:
+  std::unique_ptr<BufferHandle> GetBufferHandle(int buffer_id) override;
   int ReserveForProducer(const gfx::Size& dimensions,
                          media::VideoPixelFormat format,
                          media::VideoPixelStorage storage,
-                         int* buffer_id_to_drop);
-
-  // Indicate that a buffer held for the producer should be returned back to the
-  // pool without passing on to the consumer. This effectively is the opposite
-  // of ReserveForProducer().
-  void RelinquishProducerReservation(int buffer_id);
+                         int* buffer_id_to_drop) override;
+  void RelinquishProducerReservation(int buffer_id) override;
+  int ResurrectLastForProducer(const gfx::Size& dimensions,
+                               media::VideoPixelFormat format,
+                               media::VideoPixelStorage storage) override;
+  double GetBufferPoolUtilization() override;
 
   // Transfer a buffer from producer to consumer ownership.
   // |buffer_id| must be a buffer index previously returned by
   // ReserveForProducer(), and not already passed to HoldForConsumers().
   void HoldForConsumers(int buffer_id, int num_clients);
 
   // Indicate that one or more consumers are done with a particular buffer. This
   // effectively is the opposite of HoldForConsumers(). Once the consumers are
   // done, a buffer is returned to the pool for reuse.
   void RelinquishConsumerHold(int buffer_id, int num_clients);
 
-  // Attempt to reserve the same buffer that was relinquished in the last call
-  // to RelinquishProducerReservation(). If the buffer is not still being
-  // consumed, and has not yet been re-used since being consumed, and the
-  // specified |dimensions|, |format|, and |storage| agree with its last
-  // reservation, this will succeed. Otherwise, |kInvalidId| will be returned.
-  //
-  // A producer may assume the content of the buffer has been preserved and may
-  // also make modifications.
-  int ResurrectLastForProducer(const gfx::Size& dimensions,
-                               media::VideoPixelFormat format,
-                               media::VideoPixelStorage storage);
-
-  // Returns a snapshot of the current number of buffers in-use divided by the
-  // maximum |count_|.
-  double GetBufferPoolUtilization() const;
-
  private:
   class GpuMemoryBufferTracker;
   class SharedMemTracker;
   // Generic class to keep track of the state of a given mappable resource. Each
   // Tracker carries indication of pixel format and storage type.
   class Tracker {
    public:
     static std::unique_ptr<Tracker> CreateTracker(
         media::VideoPixelStorage storage);
 
@@ skipping 46 matching lines @@
     media::VideoPixelStorage storage_type_;
 
     // Indicates whether this Tracker is currently referenced by the producer.
     bool held_by_producer_;
 
     // Number of consumer processes which hold this Tracker.
     int consumer_hold_count_;
   };
 
   friend class base::RefCountedThreadSafe<VideoCaptureBufferPool>;
-  virtual ~VideoCaptureBufferPool();
+  ~VideoCaptureBufferPool() override;
 
   int ReserveForProducerInternal(const gfx::Size& dimensions,
                                  media::VideoPixelFormat format,
                                  media::VideoPixelStorage storage,
                                  int* tracker_id_to_drop);
 
   Tracker* GetTracker(int buffer_id);
 
   // The max number of buffers that the pool is allowed to have at any moment.
   const int count_;
@@ skipping 11 matching lines @@
   // The buffers, indexed by the first parameter, a buffer id.
   using TrackerMap = std::map<int, Tracker*>;
   TrackerMap trackers_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(VideoCaptureBufferPool);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_VIDEO_CAPTURE_BUFFER_POOL_H_