1 // Copyright 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 #ifndef CHROME_BROWSER_NETWORK_TIME_NETWORK_TIME_TRACKER_H_ 6 #define CHROME_BROWSER_NETWORK_TIME_NETWORK_TIME_TRACKER_H_ 7 8 #include "base/callback.h" 9 #include "base/memory/weak_ptr.h" 10 #include "base/threading/thread_checker.h" 11 #include "base/time/time.h" 12 #include "net/base/network_time_notifier.h" 13 14 class IOThread; 15 class NetworkTimeTrackerTest; 16 17 // A class that receives network time updates and can provide the network time 18 // for a corresponding local time. This class is not thread safe, but may live 19 // on any thread. 20 // Note that all NetworkTimeTracker instances interact with a 21 // NetworkTimeNotifier singleton that lives on the IO thread. This class 22 // enables arbitrary threads to maintain their own network time source without 23 // having to deal with the details of the Notifier's implementation. 24 class NetworkTimeTracker { 25 public: 26 // Callback for updating network time based on http responses. This callback 27 // is thread safe and should be called directly without posting to any thread. 28 // The parameters are: 29 // const base::Time& network_time - the actual time. 30 // const base::TimeDelta& resolution - how precise the reading is. 31 // const base::TimeDelta& latency - the http request's latency. 32 typedef base::Callback<void(const base::Time&, 33 const base::TimeDelta&, 34 const base::TimeDelta&)> UpdateCallback; 35 36 NetworkTimeTracker(); 37 ~NetworkTimeTracker(); 38 39 // Starts tracking network time. 40 void Start(); 41 42 struct TimeMapping { 43 TimeMapping(base::Time local_time, base::Time network_time); 44 base::Time local_time; 45 base::Time network_time; 46 }; 47 48 // Initializes from saved times to be able to compute network time before 49 // receiving accurate time from HTTP response. 50 void InitFromSavedTime(const TimeMapping& saved); 51 52 // Returns the network time corresponding to |time_ticks| if network time 53 // is available. Returns false if no network time is available yet. Can also 54 // return the error range if |uncertainty| isn't NULL. 55 bool GetNetworkTime(const base::TimeTicks& time_ticks, 56 base::Time* network_time, 57 base::TimeDelta* uncertainty) const; 58 59 // Build a callback for use in updating the network time notifier. 60 // This method must be called on the UI thread, while the callback can be 61 // called from any thread. 62 static UpdateCallback BuildNotifierUpdateCallback(); 63 received_network_time()64 bool received_network_time() const { 65 return received_network_time_; 66 } 67 68 private: 69 friend class NetworkTimeTrackerTest; 70 71 // Returns the callback used to register for time updates from the network 72 // time notifier on the IO thread. 73 net::NetworkTimeNotifier::ObserverCallback BuildObserverCallback(); 74 75 // net::NetworkTimeNotifier::ObserverCallback implementation. 76 void OnNetworkTimeUpdate( 77 const base::Time& network_time, 78 const base::TimeTicks& network_time_ticks, 79 const base::TimeDelta& network_time_uncertainty); 80 81 // Network time based on last call to UpdateNetworkTime(). 82 base::Time network_time_; 83 84 // The estimated ticks count from when |network_time_| was set based on the 85 // system's tick count. 86 base::TimeTicks network_time_ticks_; 87 88 // Uncertainty of |network_time_| based on added inaccuracies/resolution. 89 base::TimeDelta network_time_uncertainty_; 90 91 base::WeakPtrFactory<NetworkTimeTracker> weak_ptr_factory_; 92 93 base::ThreadChecker thread_checker_; 94 95 bool received_network_time_; 96 97 DISALLOW_COPY_AND_ASSIGN(NetworkTimeTracker); 98 }; 99 100 #endif // CHROME_BROWSER_NETWORK_TIME_NETWORK_TIME_TRACKER_H_ 101