Add a rate tracker that tracks rate over a given interval split up into buckets that accumulate uni…

webrtc/base/bucketratetracker.h

Index: webrtc/base/bucketratetracker.h
diff --git a/webrtc/base/bucketratetracker.h b/webrtc/base/bucketratetracker.h
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+/*
+ *  Copyright 2015 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_BASE_BUCKETRATETRACKER_H_
+#define WEBRTC_BASE_BUCKETRATETRACKER_H_
+
+#include <stdlib.h>
+#include "webrtc/base/basictypes.h"
+
+namespace rtc {
+
+// Computes units per second over a given interval by tracking the units over
+// each bucket of a given size and calculating the instantaneous rate assuming
+// that over each bucket the rate was constant.
+class BucketRateTracker {
+ public:
+  BucketRateTracker(uint32 bucket_milliseconds, size_t bucket_count);
+  virtual ~BucketRateTracker();
+
+  double ComputeCurrentRate(uint32 interval_milliseconds) const;
+
+  // Reads the current time in order to determine the appropriate bucket for
+  // these samples, and increments the count for that bucket by sample_count.
+  void AddSamples(size_t sample_count);
+
+ protected:
+  // overrideable for tests
+  virtual uint32 Time() const;
+
+ private:
+  void EnsureInitialized();
+  size_t NextBucketIndex(size_t bucket_index) const;
+
+  const uint32 bucket_milliseconds_;
+  const size_t bucket_count_;
+  size_t* sample_buckets_;
+  size_t current_bucket_;
+  uint32 bucket_start_time_;
+  uint32 initialization_time_;
+};
+
+// Computes samples per second over a given interval by dividing it into buckets
+// of one second each and calculating the rate over the appropriate number of
+// buckets.
+class IntervalRateTracker : public BucketRateTracker {
+ public:
+  explicit IntervalRateTracker(uint32 interval_seconds)
+      : BucketRateTracker(1000u, interval_seconds) {}
+};
+
+}  // namespace rtc
+
+#endif  // WEBRTC_BASE_BUCKETRATETRACKER_H_