text: // 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 MEDIA_BASE_MOVING_AVERAGE_H_
  #define MEDIA_BASE_MOVING_AVERAGE_H_
  
  #include <stddef.h>
  #include <stdint.h>
  
  #include <utility>
  #include <vector>
  
  #include "base/macros.h"
  #include "base/time/time.h"
  #include "media/base/media_export.h"
  #include "media/base/timestamp_constants.h"
  
  namespace media {
  
  // Simple class for calculating a moving average of fixed size.
  class MEDIA_EXPORT MovingAverage {
   public:
    // Creates a MovingAverage instance with space for |depth| samples.
    explicit MovingAverage(size_t depth);
    ~MovingAverage();
  
    // Adds a new sample to the average; replaces the oldest sample if |depth_|
    // has been exceeded.  Updates |total_| to the new sum of values.
    void AddSample(base::TimeDelta sample);
  
    // Returns the current average of all held samples.
    base::TimeDelta Average() const;
  
    // Returns the population standard deviation of all held samples.
    base::TimeDelta Deviation() const;
  
    // Resets the state of the class to its initial post-construction state.
    void Reset();
  
    uint64_t count() const { return count_; }
  
    base::TimeDelta max() const { return max_; }
  
    size_t depth() const { return depth_; }
  
    // |first| is min, |second| is max of all samples in the window.
    std::pair<base::TimeDelta, base::TimeDelta> GetMinAndMax();
  
   private:
    // Maximum number of elements allowed in the average.
    const size_t depth_;
    std::vector<base::TimeDelta> samples_;
  
    // Number of elements seen thus far.
    uint64_t count_ = 0;
  
    base::TimeDelta total_;
  
    // Maximum value ever seen.
    base::TimeDelta max_ = kNoTimestamp;
  
    DISALLOW_COPY_AND_ASSIGN(MovingAverage);
  };
  
  }  // namespace media
  
  #endif  // MEDIA_BASE_MOVING_AVERAGE_H_
  