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/*
* 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 MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURE_FRAME_QUEUE_H_
#define MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURE_FRAME_QUEUE_H_
#include <memory>
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).
template <typename FrameType>
class ScreenCaptureFrameQueue {
public:
ScreenCaptureFrameQueue() = default;
~ScreenCaptureFrameQueue() = default;
ScreenCaptureFrameQueue(const ScreenCaptureFrameQueue&) = delete;
ScreenCaptureFrameQueue& operator=(const ScreenCaptureFrameQueue&) = delete;
// Moves to the next frame in the queue, moving the 'current' frame to become
// the 'previous' one.
void MoveToNextFrame() { current_ = (current_ + 1) % kQueueLength; }
// 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(std::unique_ptr<FrameType> frame) {
frames_[current_] = std::move(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() {
for (int i = 0; i < kQueueLength; i++) {
frames_[i].reset();
}
current_ = 0;
}
FrameType* current_frame() const { return frames_[current_].get(); }
FrameType* previous_frame() const {
return frames_[(current_ + kQueueLength - 1) % kQueueLength].get();
}
private:
// Index of the current frame.
int current_ = 0;
static const int kQueueLength = 2;
std::unique_ptr<FrameType> frames_[kQueueLength];
};
} // namespace webrtc
#endif // MODULES_DESKTOP_CAPTURE_SCREEN_CAPTURE_FRAME_QUEUE_H_