RTCStatsCollector and RTCPeerConnectionStats added

webrtc/stats/rtcstatscollector.h

+/*
+ *  Copyright 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.
+ */
+
+#ifndef WEBRTC_STATS_RTCSTATSCOLLECTOR_H_
+#define WEBRTC_STATS_RTCSTATSCOLLECTOR_H_
+
+#include <memory>
+
+#include "webrtc/api/rtcstats_objects.h"
+#include "webrtc/api/rtcstatsreport.h"
+#include "webrtc/base/scoped_ref_ptr.h"
+#include "webrtc/base/timing.h"
+
+namespace webrtc {
+
+class PeerConnection;
+
+// All calls to the collector and gathering of stats is performed on the
+// signaling thread. A stats report is cached for |cache_lifetime_| ms.
+class RTCStatsCollector {
+ public:
+  explicit RTCStatsCollector(
+      PeerConnection* pc,
+      double cache_lifetime = 0.05,
+      std::unique_ptr<rtc::Timing> timing = std::unique_ptr<rtc::Timing>(
+          new rtc::Timing()));
+
+  // Gets a recent stats report. If there is a report cached that is still fresh
+  // it is returned, otherwise new stats are gathered and returned. A report is
+  // considered fresh for |cache_lifetime_| ms. const RTCStatsReports are safe
+  // to use across multiple threads and may be destructed on any thread.
+  rtc::scoped_refptr<const RTCStatsReport> GetStatsReport();
+  // Clears the cache's reference to the most recent stats report. Subsequently
+  // calling |GetStatsReport| guarantees fresh stats.
+  void ClearCachedStatsReport();
+
+ private:
+  bool IsOnSignalingThread() const;
+
+  std::unique_ptr<RTCPeerConnectionStats> ProducePeerConnectionStats() const;
+
+  PeerConnection* const pc_;
+  mutable std::unique_ptr<rtc::Timing> timing_;
+  // Time relative to the UNIX epoch (Jan 1, 1970, UTC), in seconds.
+  double cache_timestamp_;
+  double cache_lifetime_;  // In seconds.
+  rtc::scoped_refptr<const RTCStatsReport> cached_report_;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_STATS_RTCSTATSCOLLECTOR_H_