Landing Recent QUIC changes until 7/18/2016 11:21:53 UTC

net/quic/quic_alarm.cc

 // Copyright 2013 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.
 
 #include "net/quic/quic_alarm.h"
 
 #include "base/logging.h"
 #include "net/quic/quic_flags.h"
 
 namespace net {
@@ skipping 21 matching lines @@
 
 void QuicAlarm::Update(QuicTime new_deadline, QuicTime::Delta granularity) {
   if (!new_deadline.IsInitialized()) {
     Cancel();
     return;
   }
   if (std::abs((new_deadline - deadline_).ToMicroseconds()) <
       granularity.ToMicroseconds()) {
     return;
   }
-  Cancel();
-  Set(new_deadline);
+  if (FLAGS_quic_change_alarms_efficiently) {
+    const bool was_set = IsSet();
+    deadline_ = new_deadline;
+    if (was_set) {
+      UpdateImpl();
+    } else {
+      SetImpl();
+    }
+  } else {
+    Cancel();
+    Set(new_deadline);
+  }
 }
 
 bool QuicAlarm::IsSet() const {
   return deadline_.IsInitialized();
 }
 
 void QuicAlarm::Fire() {
   if (!IsSet()) {
     return;
   }
 
   deadline_ = QuicTime::Zero();
   delegate_->OnAlarm();
 }
 
+void QuicAlarm::UpdateImpl() {
+  // CancelImpl and SetImpl take the new deadline by way of the deadline_
+  // member, so save and restore deadline_ before canceling.
+  const QuicTime new_deadline = deadline_;
+
+  deadline_ = QuicTime::Zero();
+  CancelImpl();
+
+  deadline_ = new_deadline;
+  SetImpl();
+}
+
 }  // namespace net