Add class which periodically computes statistics.

webrtc/video/stats_counter.cc

Index: webrtc/video/stats_counter.cc
diff --git a/webrtc/video/stats_counter.cc b/webrtc/video/stats_counter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..918e998c4db858580aa7d0ef338f6aaf38a72432
--- /dev/null
+++ b/webrtc/video/stats_counter.cc
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+/*
+ *  Copyright (c) 2016 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.
+ */
+
+#include "webrtc/video/stats_counter.h"
+
+#include <algorithm>
+
+#include "webrtc/system_wrappers/include/clock.h"
+
+namespace webrtc {
+
+namespace {
+// Periodic time interval for processing samples.
+const int64_t kProcessIntervalMs = 2000;
+}  // namespace
+
+// Class holding periodically computed metrics.
+class AggregatedCounter {
+ public:
+  AggregatedCounter() : sum_(0) {}
+  ~AggregatedCounter() {}
+
+  void Add(int sample) {
+    sum_ += sample;
+    ++stats_.num_samples;
+    if (stats_.num_samples == 1) {
+      stats_.min = sample;
+      stats_.max = sample;
+    }
+    stats_.min = std::min(sample, stats_.min);
+    stats_.max = std::max(sample, stats_.max);
+  }
+
+  AggregatedStats ComputeStats() {
+    Compute();
+    return stats_;
+  }
+
+ private:
+  void Compute() {
+    if (stats_.num_samples == 0)
+      return;
+
+    stats_.average = (sum_ + stats_.num_samples / 2) / stats_.num_samples;
+  }
+  int64_t sum_;
+  AggregatedStats stats_;
+};
+
+// StatsCounter class.
+StatsCounter::StatsCounter(Clock* clock,
+                           bool include_empty_intervals,
+                           StatsCounterObserver* observer)
+    : max_(0),
+      sum_(0),
+      num_samples_(0),
+      last_sum_(0),
+      clock_(clock),
+      include_empty_intervals_(include_empty_intervals),
+      observer_(observer),
+      aggregated_counter_(new AggregatedCounter()),
+      last_process_time_ms_(-1) {}
+
+StatsCounter::~StatsCounter() {}
+
+AggregatedStats StatsCounter::GetStats() {
+  return aggregated_counter_->ComputeStats();
+}
+
+bool StatsCounter::TimeToProcess() {
+  int64_t now = clock_->TimeInMilliseconds();
+  if (last_process_time_ms_ == -1)
+    last_process_time_ms_ = now;
+
+  int64_t diff_ms = now - last_process_time_ms_;
+  if (diff_ms < kProcessIntervalMs)
+    return false;
+
+  // Advance number of complete kProcessIntervalMs that have passed.
+  int64_t num_intervals = diff_ms / kProcessIntervalMs;
+  last_process_time_ms_ += num_intervals * kProcessIntervalMs;
+
+  // Add zero for intervals without samples.
+  if (include_empty_intervals_) {
+    for (int64_t i = 0; i < num_intervals - 1; ++i) {
+      aggregated_counter_->Add(0);
+      if (observer_)
+        observer_->OnMetricUpdated(0);
+    }
+  }
+  return true;
+}
+
+void StatsCounter::Set(int sample) {
+  TryProcess();
+  ++num_samples_;
+  sum_ = sample;
+}
+
+void StatsCounter::Add(int sample) {
+  TryProcess();
+  ++num_samples_;
+  sum_ += sample;
+
+  if (num_samples_ == 1)
+    max_ = sample;
+  max_ = std::max(sample, max_);
+}
+
+void StatsCounter::TryProcess() {
+  if (!TimeToProcess())
+    return;
+
+  int metric;
+  if (GetMetric(&metric)) {
+    aggregated_counter_->Add(metric);
+    if (observer_)
+      observer_->OnMetricUpdated(metric);
+  }
+  last_sum_ = sum_;
+  sum_ = 0;
+  max_ = 0;
+  num_samples_ = 0;
+}
+
+// StatsCounter sub-classes.
+AvgCounter::AvgCounter(Clock* clock, StatsCounterObserver* observer)
+    : StatsCounter(clock,
+                   false,  // |include_empty_intervals|
+                   observer) {}
+
+void AvgCounter::Add(int sample) {
+  StatsCounter::Add(sample);
+}
+
+bool AvgCounter::GetMetric(int* metric) const {
+  if (num_samples_ == 0)
+    return false;
+  *metric = (sum_ + num_samples_ / 2) / num_samples_;
+  return true;
+}
+
+MaxCounter::MaxCounter(Clock* clock, StatsCounterObserver* observer)
+    : StatsCounter(clock,
+                   false,  // |include_empty_intervals|
+                   observer) {}
+
+void MaxCounter::Add(int sample) {
+  StatsCounter::Add(sample);
+}
+
+bool MaxCounter::GetMetric(int* metric) const {
+  if (num_samples_ == 0)
+    return false;
+  *metric = max_;
+  return true;
+}
+
+PercentCounter::PercentCounter(Clock* clock, StatsCounterObserver* observer)
+    : StatsCounter(clock,
+                   false,  // |include_empty_intervals|
+                   observer) {}
+
+void PercentCounter::Add(bool sample) {
+  StatsCounter::Add(sample ? 1 : 0);
+}
+
+bool PercentCounter::GetMetric(int* metric) const {
+  if (num_samples_ == 0)
+    return false;
+  *metric = (sum_ * 100 + num_samples_ / 2) / num_samples_;
+  return true;
+}
+
+PermilleCounter::PermilleCounter(Clock* clock, StatsCounterObserver* observer)
+    : StatsCounter(clock,
+                   false,  // |include_empty_intervals|
+                   observer) {}
+
+void PermilleCounter::Add(bool sample) {
+  StatsCounter::Add(sample ? 1 : 0);
+}
+
+bool PermilleCounter::GetMetric(int* metric) const {
+  if (num_samples_ == 0)
+    return false;
+  *metric = (sum_ * 1000 + num_samples_ / 2) / num_samples_;
+  return true;
+}
+
+RateCounter::RateCounter(Clock* clock, StatsCounterObserver* observer)
+    : StatsCounter(clock,
+                   true,  // |include_empty_intervals|
+                   observer) {}
+
+void RateCounter::Add(int sample) {
+  StatsCounter::Add(sample);
+}
+
+bool RateCounter::GetMetric(int* metric) const {
+  if (num_samples_ == 0)
+    return false;
+  *metric = (sum_ * 1000 + kProcessIntervalMs / 2) / kProcessIntervalMs;
+  return true;
+}
+
+RateAccCounter::RateAccCounter(Clock* clock, StatsCounterObserver* observer)
+    : StatsCounter(clock,
+                   true,  // |include_empty_intervals|
+                   observer) {}
+
+void RateAccCounter::Set(int sample) {
+  StatsCounter::Set(sample);
+}
+
+bool RateAccCounter::GetMetric(int* metric) const {
+  if (num_samples_ == 0 || last_sum_ > sum_)
+    return false;
+  *metric =
+      ((sum_ - last_sum_) * 1000 + kProcessIntervalMs / 2) / kProcessIntervalMs;
+  return true;
+}
+
+}  // namespace webrtc