1// Copyright 2014 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 <cmath>
6
7#include "cc/base/rolling_time_delta_history.h"
8
9namespace cc {
10
11RollingTimeDeltaHistory::RollingTimeDeltaHistory(size_t max_size)
12    : max_size_(max_size) {}
13
14RollingTimeDeltaHistory::~RollingTimeDeltaHistory() {}
15
16void RollingTimeDeltaHistory::InsertSample(base::TimeDelta time) {
17  if (max_size_ == 0)
18    return;
19
20  if (sample_set_.size() == max_size_) {
21    sample_set_.erase(chronological_sample_deque_.front());
22    chronological_sample_deque_.pop_front();
23  }
24
25  TimeDeltaMultiset::iterator it = sample_set_.insert(time);
26  chronological_sample_deque_.push_back(it);
27}
28
29void RollingTimeDeltaHistory::Clear() {
30  chronological_sample_deque_.clear();
31  sample_set_.clear();
32}
33
34base::TimeDelta RollingTimeDeltaHistory::Percentile(double percent) const {
35  if (sample_set_.size() == 0)
36    return base::TimeDelta();
37
38  double fraction = percent / 100.0;
39
40  if (fraction <= 0.0)
41    return *(sample_set_.begin());
42
43  if (fraction >= 1.0)
44    return *(sample_set_.rbegin());
45
46  size_t num_smaller_samples =
47      static_cast<size_t>(std::ceil(fraction * sample_set_.size())) - 1;
48
49  if (num_smaller_samples > sample_set_.size() / 2) {
50    size_t num_larger_samples = sample_set_.size() - num_smaller_samples - 1;
51    TimeDeltaMultiset::const_reverse_iterator it = sample_set_.rbegin();
52    for (size_t i = 0; i < num_larger_samples; i++)
53      it++;
54    return *it;
55  }
56
57  TimeDeltaMultiset::const_iterator it = sample_set_.begin();
58  for (size_t i = 0; i < num_smaller_samples; i++)
59    it++;
60  return *it;
61}
62
63}  // namespace cc
64