Modify ScreenCaptureFrameQueue into a template

webrtc/modules/desktop_capture/screen_capture_frame_queue.h

-/*
- *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-#ifndef WEBRTC_MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURE_FRAME_QUEUE_H_
-#define WEBRTC_MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURE_FRAME_QUEUE_H_
-
-#include <memory>
-
-#include "webrtc/modules/desktop_capture/shared_desktop_frame.h"
-#include "webrtc/typedefs.h"
-
-namespace webrtc {
-class DesktopFrame;
-}  // namespace webrtc
-
-namespace webrtc {
-
-// Represents a queue of reusable video frames. Provides access to the 'current'
-// frame - the frame that the caller is working with at the moment, and to the
-// 'previous' frame - the predecessor of the current frame swapped by
-// MoveToNextFrame() call, if any.
-//
-// The caller is expected to (re)allocate frames if current_frame() returns
-// NULL. The caller can mark all frames in the queue for reallocation (when,
-// say, frame dimensions change). The queue records which frames need updating
-// which the caller can query.
-//
-// Frame consumer is expected to never hold more than kQueueLength frames
-// created by this function and it should release the earliest one before trying
-// to capture a new frame (i.e. before MoveToNextFrame() is called).
-class ScreenCaptureFrameQueue {
- public:
-  ScreenCaptureFrameQueue();
-  ~ScreenCaptureFrameQueue();
-
-  // Moves to the next frame in the queue, moving the 'current' frame to become
-  // the 'previous' one.
-  void MoveToNextFrame();
-
-  // Replaces the current frame with a new one allocated by the caller. The
-  // existing frame (if any) is destroyed. Takes ownership of |frame|.
-  void ReplaceCurrentFrame(DesktopFrame* frame);
-
-  // Marks all frames obsolete and resets the previous frame pointer. No
-  // frames are freed though as the caller can still access them.
-  void Reset();
-
-  SharedDesktopFrame* current_frame() const {
-    return frames_[current_].get();
-  }
-
-  SharedDesktopFrame* previous_frame() const {
-    return frames_[(current_ + kQueueLength - 1) % kQueueLength].get();
-  }
-
- private:
-  // Index of the current frame.
-  int current_;
-
-  static const int kQueueLength = 2;
-  std::unique_ptr<SharedDesktopFrame> frames_[kQueueLength];
-
-  RTC_DISALLOW_COPY_AND_ASSIGN(ScreenCaptureFrameQueue);
-};
-
-}  // namespace webrtc
-
-#endif  // WEBRTC_MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURE_FRAME_QUEUE_H_