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

webrtc/base/bucketratetracker.h

+/*
+ *  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, uint32 interval_buckets);

[noahric, 2015/08/07 23:56:38]

maybe size_t bucket_count? (and bucket_count_)

[tpsiaki, 2015/08/11 18:33:27]

Done.

+  virtual ~BucketRateTracker();
+
+  size_t units_second() const;

[noahric, 2015/08/07 23:56:38]

double? Also since this is simply returning a field, you should name it
something like ComputeCurrentRate. I wouldn't overly worry about matching
ratetracker.h, since I don't think that API is super obvious.

Another thing to consider is to have interval_buckets/bucket_count be
max_bucket_count, and then have this function take a time to return the rate
over. That way send stats proxy could set something like 15-30s, and then return
the full rate tracker when asked about stats (instead of just a number), and the
caller could decide how much of the history to use at any point.

[tpsiaki, 2015/08/11 18:33:27]

Done.

+  void Update(size_t units);

[noahric, 2015/08/07 23:56:38]

I know this matches RateTracker, but I feel like AddSample or something like
that would be more clear. Also a short comment, explaining that it uses the
current time.

[tpsiaki, 2015/08/11 18:33:27]

Done.

+
+ protected:
+  // overrideable for tests
+  virtual uint32 Time() const;
+
+ private:
+  void EnsureInitialized();
+
+  const uint32 bucket_milliseconds_;
+  const uint32 interval_buckets_;
+  size_t* unit_buckets_;
+  uint32 current_bucket_;
+  uint32 bucket_start_time_;
+  uint32 initialization_time_;
+};
+
+// Computes units 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_