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// Copyright (c) 2011 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 REMOTING_BASE_RATE_COUNTER_H_
#define REMOTING_BASE_RATE_COUNTER_H_
#include <queue>
#include <utility>
#include "base/basictypes.h"
#include "base/threading/non_thread_safe.h"
#include "base/time/time.h"
namespace remoting {
// Measures average rate per second of a sequence of point rate samples
// over a specified time window. This can be used to measure bandwidth, frame
// rates, etc.
class RateCounter : public base::NonThreadSafe {
public:
// Constructs a rate counter over the specified |time_window|.
explicit RateCounter(base::TimeDelta time_window);
virtual ~RateCounter();
// Records a point event count to include in the rate.
void Record(int64 value);
// Returns the rate-per-second of values recorded over the time window.
// Note that rates reported before |time_window| has elapsed are not accurate.
double Rate();
// Overrides the current time for testing.
void SetCurrentTimeForTest(base::Time current_time);
private:
// Type used to store data points with timestamps.
typedef std::pair<base::Time, int64> DataPoint;
// Removes data points more than |time_window| older than |current_time|.
void EvictOldDataPoints(base::Time current_time);
// Returns the current time specified for test, if set, or base::Time::Now().
base::Time CurrentTime() const;
// Time window over which to calculate the rate.
const base::TimeDelta time_window_;
// Queue containing data points in the order in which they were recorded.
std::queue<DataPoint> data_points_;
// Sum of values in |data_points_|.
int64 sum_;
// If set, used to calculate the running average, in place of Now().
base::Time current_time_for_test_;
DISALLOW_COPY_AND_ASSIGN(RateCounter);
};
} // namespace remoting
#endif // REMOTING_BASE_RATE_COUNTER_H_
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