content/browser/download/rate_estimator.h

   1 // Copyright 2013 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 #ifndef CONTENT_BROWSER_DOWNLOAD_RATE_ESTIMATOR_H_
   6 #define CONTENT_BROWSER_DOWNLOAD_RATE_ESTIMATOR_H_
   7
   8 #include <string>
   9 #include <vector>
  10
  11 #include "base/basictypes.h"
  12 #include "base/time/time.h"
  13 #include "content/common/content_export.h"
  14
  15 namespace content {
  16
  17 // RateEstimator generates rate estimates based on recent activity.
  18 //
  19 // Internally it uses a fixed-size ring buffer, and develops estimates
  20 // based on a small sliding window of activity.
  21 class CONTENT_EXPORT RateEstimator {
  22  public:
  23   RateEstimator();
  24   RateEstimator(base::TimeDelta bucket_time,
  25                 size_t num_buckets,
  26                 base::TimeTicks now);
  27   ~RateEstimator();
  28
  29   // Increment the counter by |count|. The first variant uses the current time,
  30   // the second variant provides the time that |count| is observed.
  31   void Increment(uint32 count);
  32   void Increment(uint32 count, base::TimeTicks now);
  33
  34   // Get a rate estimate, in terms of counts/second. The first variant uses the
  35   // current time, the second variant provides the time.
  36   uint64 GetCountPerSecond() const;
  37   uint64 GetCountPerSecond(base::TimeTicks now) const;
  38
  39  private:
  40   void ClearOldBuckets(base::TimeTicks now);
  41   void ResetBuckets(base::TimeTicks now);
  42
  43   std::vector<uint32> history_;
  44   base::TimeDelta bucket_time_;
  45   size_t oldest_index_;
  46   size_t bucket_count_;
  47   base::TimeTicks oldest_time_;
  48 };
  49
  50 }  // namespace content
  51
  52 #endif  // CONTENT_BROWSER_DOWNLOAD_RATE_ESTIMATOR_H_