text: // Copyright (c) 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 MEDIA_CAPTURE_CONTENT_SMOOTH_EVENT_SAMPLER_H_
  #define MEDIA_CAPTURE_CONTENT_SMOOTH_EVENT_SAMPLER_H_
  
  #include "base/macros.h"
  #include "base/time/time.h"
  #include "media/capture/capture_export.h"
  
  namespace media {
  
  // Filters a sequence of events to achieve a target frequency.
  class CAPTURE_EXPORT SmoothEventSampler {
   public:
    explicit SmoothEventSampler(base::TimeDelta min_capture_period);
  
    SmoothEventSampler(const SmoothEventSampler&) = delete;
    SmoothEventSampler& operator=(const SmoothEventSampler&) = delete;
  
    // Get/Set minimum capture period. When setting a new value, the state of the
    // sampler is retained so that sampling will continue smoothly.
    base::TimeDelta min_capture_period() const { return min_capture_period_; }
    void SetMinCapturePeriod(base::TimeDelta p);
  
    // Add a new event to the event history, and consider whether it ought to be
    // sampled. The event is not recorded as a sample until RecordSample() is
    // called.
    void ConsiderPresentationEvent(base::TimeTicks event_time);
  
    // Returns true if the last event considered should be sampled.
    bool ShouldSample() const;
  
    // Operates on the last event added by ConsiderPresentationEvent(), marking
    // it as sampled. After this point we are current in the stream of events, as
    // we have sampled the most recent event.
    void RecordSample();
  
    // Returns true if ConsiderPresentationEvent() has been called since the last
    // call to RecordSample().
    bool HasUnrecordedEvent() const;
  
   private:
    base::TimeDelta min_capture_period_;
    base::TimeDelta token_bucket_capacity_;
  
    base::TimeTicks current_event_;
    base::TimeTicks last_sample_;
    base::TimeDelta token_bucket_;
  };
  
  }  // namespace media
  
  #endif  // MEDIA_CAPTURE_CONTENT_SMOOTH_EVENT_SAMPLER_H_
  