cc/base/rolling_time_delta_history.cc

   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
   9 namespace cc {
  10
  11 RollingTimeDeltaHistory::RollingTimeDeltaHistory(size_t max_size)
  12     : max_size_(max_size) {}
  13
  14 RollingTimeDeltaHistory::~RollingTimeDeltaHistory() {}
  15
  16 void 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
  29 void RollingTimeDeltaHistory::Clear() {
  30   chronological_sample_deque_.clear();
  31   sample_set_.clear();
  32 }
  33
  34 base::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