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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_DOWNLOAD_PUBLIC_COMMON_RATE_ESTIMATOR_H_
#define COMPONENTS_DOWNLOAD_PUBLIC_COMMON_RATE_ESTIMATOR_H_
#include <stddef.h>
#include <stdint.h>
#include <vector>
#include "base/time/time.h"
#include "components/download/public/common/download_export.h"
namespace download {
// RateEstimator generates rate estimates based on recent activity.
//
// Internally it uses a fixed-size ring buffer, and develops estimates
// based on a small sliding window of activity.
class COMPONENTS_DOWNLOAD_EXPORT RateEstimator {
public:
RateEstimator();
RateEstimator(base::TimeDelta bucket_time,
size_t num_buckets,
base::TimeTicks now);
~RateEstimator();
// Increment the counter by |count|. The first variant uses the current time,
// the second variant provides the time that |count| is observed.
void Increment(uint32_t count);
void Increment(uint32_t count, base::TimeTicks now);
// Get a rate estimate, in terms of counts/second. The first variant uses the
// current time, the second variant provides the time.
uint64_t GetCountPerSecond() const;
uint64_t GetCountPerSecond(base::TimeTicks now) const;
private:
void ClearOldBuckets(base::TimeTicks now);
void ResetBuckets(base::TimeTicks now);
std::vector<uint32_t> history_;
base::TimeDelta bucket_time_;
size_t oldest_index_;
size_t bucket_count_;
base::TimeTicks oldest_time_;
};
} // namespace download
#endif // COMPONENTS_DOWNLOAD_PUBLIC_COMMON_RATE_ESTIMATOR_H_
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