RTCStatsCollector and RTCPeerConnectionStats added

webrtc/stats/rtcstatscollector.cc

+/*
+ *  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.
+ */
+
+#include "webrtc/stats/rtcstatscollector.h"
+
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "webrtc/base/checks.h"
+
+namespace webrtc {
+
+RTCStatsCollector::RTCStatsCollector(
+    PeerConnection* pc,
+    double cache_lifetime,
+    std::unique_ptr<rtc::Timing> timing)
+    : pc_(pc),
+      timing_(std::move(timing)),
+      cache_timestamp_(0.0),
+      cache_lifetime_(cache_lifetime) {
+  RTC_DCHECK(pc_);
+  RTC_DCHECK(timing_);
+  RTC_DCHECK(IsSignalingThread());
+  RTC_DCHECK_GE(cache_lifetime_, 0.0);
+}
+
+rtc::scoped_refptr<const RTCStatsReport> RTCStatsCollector::GetStatsReport() {
+  RTC_DCHECK(IsSignalingThread());
+  double now = GetTimeNowMs();

[hta-webrtc, 2016/08/24 13:02:15]

Milliseconds again?

[hbos, 2016/08/24 14:28:00]

Ah, I forgot about having changed stats to use seconds. Updated the collector to
do so as well.

+  if (cached_report_ && now - cache_timestamp_ <= cache_lifetime_)
+    return cached_report_;
+  cache_timestamp_ = now;
+
+  rtc::scoped_refptr<RTCStatsReport> report = RTCStatsReport::Create();
+  report->AddStats(ProducePeerConnectionStats());
+
+  cached_report_ = report;
+  return cached_report_;
+}
+
+void RTCStatsCollector::ClearCachedStatsReport() {
+  RTC_DCHECK(IsSignalingThread());
+  cached_report_ = nullptr;
+}
+
+bool RTCStatsCollector::IsSignalingThread() const {
+  return pc_->session()->signaling_thread()->IsCurrent();
+}
+
+double RTCStatsCollector::GetTimeNowMs() const {
+  return timing_->TimerNow() * rtc::kNumMillisecsPerSec;

[hta-webrtc, 2016/08/24 13:02:15]

If you keep cache lifetime in seconds (0.05 by default), this function is
superfluous.

[hbos, 2016/08/24 14:28:00]

Done.

+}
+
+std::unique_ptr<RTCPeerConnectionStats>
+RTCStatsCollector::ProducePeerConnectionStats() const {
+  // TODO(hbos): If data channels are removed from the peer connection this will
+  // yield incorrect counts. Address before closing crbug.com/636818.

[hta-webrtc, 2016/08/24 13:02:15]

Spec reference:
https://w3c.github.io/webrtc-stats/webrtc-stats.html#pcstats-dict* - it is good
to have the link in the code.

And yes, it's wrong; these are supposed to be incrementing counters. I'll get
the spec updated to clarify that.

[hbos, 2016/08/24 14:28:00]

Done.

+  uint32_t data_channels_opened = 0;
+  const std::vector<rtc::scoped_refptr<DataChannel>>& data_channels =
+      pc_->sctp_data_channels();
+  for (const rtc::scoped_refptr<DataChannel>& data_channel : data_channels) {
+    if (data_channel->state() == DataChannelInterface::kOpen)
+      ++data_channels_opened;
+  }
+  // There is always just one |RTCPeerConnectionStats| so its |id| can be a
+  // constant.
+  std::unique_ptr<RTCPeerConnectionStats> stats(
+    new RTCPeerConnectionStats("RTCPeerConnection", cache_timestamp_));
+  stats->data_channels_opened = data_channels_opened;
+  stats->data_channels_closed = static_cast<uint32_t>(data_channels.size()) -
+                                data_channels_opened;
+  return stats;
+}
+
+}  // namespace webrtc