Land Recent QUIC Changes.

net/quic/congestion_control/rtt_stats.h

+// Copyright (c) 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// A convenience class to store rtt samples and calculate smoothed rtt.
+
+#ifndef NET_QUIC_CONGESTION_CONTROL_RTT_STATS_H_
+#define NET_QUIC_CONGESTION_CONTROL_RTT_STATS_H_
+
+#include <algorithm>
+
+#include "base/basictypes.h"
+#include "net/quic/quic_protocol.h"
+#include "net/quic/quic_time.h"
+
+namespace net {
+
+class NET_EXPORT_PRIVATE RttStats {
+ public:
+  RttStats();
+
+  // Returns true if any RTT measurements have been made.
+  bool HasUpdates() const;
+
+  // Updates the RTT from an incoming ack which is received |send_delta| after
+  // the packet is sent and the peer reports the ack being delayed |ack_delay|.
+  void UpdateRtt(QuicTime::Delta send_delta, QuicTime::Delta ack_delay);
+
+  QuicTime::Delta SmoothedRtt() const;
+
+  // Sets an initial RTT to be used for SmoothedRtt before any RTT updates.
+  void set_initial_rtt_us(int64 initial_rtt_us) {
+    initial_rtt_us_ = initial_rtt_us;
+  }
+
+  QuicTime::Delta latest_rtt() const {
+    return latest_rtt_;
+  }
+
+  QuicTime::Delta min_rtt() const {
+    return min_rtt_;
+  }
+
+  QuicTime::Delta mean_deviation() const {
+    return mean_deviation_;
+  }
+
+ private:
+  QuicTime::Delta latest_rtt_;
+  QuicTime::Delta min_rtt_;
+  QuicTime::Delta smoothed_rtt_;
+  // Mean RTT deviation during this session.
+  // Approximation of standard deviation, the error is roughly 1.25 times
+  // larger than the standard deviation, for a normally distributed signal.
+  QuicTime::Delta mean_deviation_;
+  int64 initial_rtt_us_;
+};
+
+}  // namespace net
+
+#endif  // NET_QUIC_CONGESTION_CONTROL_RTT_STATS_H_