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| 1 // Copyright (c) 2013 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 #include "net/base/network_time_notifier.h" | |
| 6 | |
| 7 #include "base/basictypes.h" | |
| 8 #include "base/bind.h" | |
| 9 #include "base/i18n/time_formatting.h" | |
| 10 #include "base/location.h" | |
| 11 #include "base/message_loop/message_loop.h" | |
| 12 #include "base/stl_util.h" | |
| 13 #include "base/strings/utf_string_conversions.h" | |
| 14 | |
| 15 namespace { | |
| 16 | |
| 17 // Clock resolution is platform dependent. | |
| 18 #if defined(OS_WIN) | |
| 19 const int64 kTicksResolutionMs = base::Time::kMinLowResolutionThresholdMs; | |
| 20 #else | |
| 21 const int64 kTicksResolutionMs = 1; // Assume 1ms for non-windows platforms. | |
| 22 #endif | |
| 23 | |
| 24 // Number of time measurements performed in a given network time calculation. | |
| 25 const int kNumTimeMeasurements = 5; | |
| 26 | |
| 27 } // namespace | |
| 28 | |
| 29 namespace net { | |
| 30 | |
| 31 NetworkTimeNotifier::NetworkTimeNotifier( | |
| 32 scoped_ptr<base::TickClock> tick_clock) { | |
| 33 tick_clock_ = tick_clock.Pass(); | |
| 34 } | |
| 35 | |
| 36 NetworkTimeNotifier::~NetworkTimeNotifier() {} | |
| 37 | |
| 38 void NetworkTimeNotifier::UpdateNetworkTime(const base::Time& network_time, | |
| 39 const base::TimeDelta& resolution, | |
| 40 const base::TimeDelta& latency, | |
| 41 const base::TimeTicks& post_time) { | |
| 42 DCHECK(thread_checker_.CalledOnValidThread()); | |
| 43 DVLOG(1) << "Network time updating to " | |
| 44 << base::UTF16ToUTF8( | |
| 45 base::TimeFormatFriendlyDateAndTime(network_time)); | |
| 46 // Update network time on every request to limit dependency on ticks lag. | |
| 47 // TODO(mad): Find a heuristic to avoid augmenting the | |
| 48 // network_time_uncertainty_ too much by a particularly long latency. | |
| 49 // Maybe only update when the the new time either improves in accuracy or | |
| 50 // drifts too far from |network_time_|. | |
| 51 network_time_ = network_time; | |
| 52 | |
| 53 // Calculate the delay since the network time was received. | |
| 54 base::TimeTicks now = tick_clock_->NowTicks(); | |
| 55 base::TimeDelta task_delay = now - post_time; | |
| 56 // Estimate that the time was set midway through the latency time. | |
| 57 network_time_ticks_ = now - task_delay - latency / 2; | |
| 58 | |
| 59 // Can't assume a better time than the resolution of the given time | |
| 60 // and 5 ticks measurements are involved, each with their own uncertainty. | |
| 61 // 1 & 2 are the ones used to compute the latency, 3 is the Now() from when | |
| 62 // this task was posted, 4 is the Now() above and 5 will be the Now() used in | |
| 63 // GetNetworkTime(). | |
| 64 network_time_uncertainty_ = | |
| 65 resolution + latency + kNumTimeMeasurements * | |
| 66 base::TimeDelta::FromMilliseconds(kTicksResolutionMs); | |
| 67 | |
| 68 for (size_t i = 0; i < observers_.size(); ++i) { | |
| 69 base::MessageLoop::current()->PostTask( | |
| 70 FROM_HERE, | |
| 71 base::Bind(observers_[i], | |
| 72 network_time_, | |
| 73 network_time_ticks_, | |
| 74 network_time_uncertainty_)); | |
| 75 } | |
| 76 } | |
| 77 | |
| 78 void NetworkTimeNotifier::AddObserver( | |
| 79 const ObserverCallback& observer_callback) { | |
| 80 DCHECK(thread_checker_.CalledOnValidThread()); | |
| 81 observers_.push_back(observer_callback); | |
| 82 if (!network_time_.is_null()) { | |
| 83 base::MessageLoop::current()->PostTask( | |
| 84 FROM_HERE, | |
| 85 base::Bind(observer_callback, | |
| 86 network_time_, | |
| 87 network_time_ticks_, | |
| 88 network_time_uncertainty_)); | |
| 89 } | |
| 90 } | |
| 91 | |
| 92 } // namespace net | |
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Chromium Code Reviews
Issue 271853004:
Merge NetworkTimeNotifier to NetworkTimeTracker (Closed)
Base URL: svn://svn.chromium.org/chrome/trunk/src