media/base/moving_average.cc

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "media/base/moving_average.h"
   6
   7 #include <algorithm>
   8
   9 namespace media {
  10
  11 MovingAverage::MovingAverage(size_t depth)
  12     : depth_(depth), count_(0), samples_(depth_) {
  13 }
  14
  15 MovingAverage::~MovingAverage() {
  16 }
  17
  18 void MovingAverage::AddSample(base::TimeDelta sample) {
  19   // |samples_| is zero-initialized, so |oldest| is also zero before |count_|
  20   // exceeds |depth_|.
  21   base::TimeDelta& oldest = samples_[count_++ % depth_];
  22   total_ += sample - oldest;
  23   oldest = sample;
  24 }
  25
  26 base::TimeDelta MovingAverage::Average() const {
  27   DCHECK_GT(count_, 0u);
  28
  29   // TODO(dalecurtis): Consider limiting |depth| to powers of two so that we can
  30   // replace the integer divide with a bit shift operation.
  31
  32   return total_ / std::min(static_cast<uint64_t>(depth_), count_);
  33 }
  34
  35 void MovingAverage::Reset() {
  36   count_ = 0;
  37   total_ = base::TimeDelta();
  38   std::fill(samples_.begin(), samples_.end(), base::TimeDelta());
  39 }
  40
  41 }  // namespace media