// 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.

#include "media/base/moving_average.h"

#include <algorithm>

namespace media {

MovingAverage::MovingAverage(size_t depth)
    : depth_(depth), count_(0), samples_(depth_) {
}

MovingAverage::~MovingAverage() {
}

void MovingAverage::AddSample(base::TimeDelta sample) {
  // |samples_| is zero-initialized, so |oldest| is also zero before |count_|
  // exceeds |depth_|.
  base::TimeDelta& oldest = samples_[count_++ % depth_];
  total_ += sample - oldest;
  oldest = sample;
}

base::TimeDelta MovingAverage::Average() const {
  DCHECK_GT(count_, 0u);

  // TODO(dalecurtis): Consider limiting |depth| to powers of two so that we can
  // replace the integer divide with a bit shift operation.

  return total_ / std::min(static_cast<uint64_t>(depth_), count_);
}

void MovingAverage::Reset() {
  count_ = 0;
  total_ = base::TimeDelta();
  std::fill(samples_.begin(), samples_.end(), base::TimeDelta());
}

}  // namespace media