1 // Copyright 2014 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 COMPONENTS_NETWORK_TIME_NETWORK_TIME_TRACKER_H_ 6 #define COMPONENTS_NETWORK_TIME_NETWORK_TIME_TRACKER_H_ 7 8 #include "base/memory/scoped_ptr.h" 9 #include "base/threading/thread_checker.h" 10 #include "base/time/time.h" 11 12 class PrefRegistrySimple; 13 class PrefService; 14 15 namespace base { 16 class TickClock; 17 } 18 19 namespace network_time { 20 21 // A class that receives network time updates and can provide the network time 22 // for a corresponding local time. This class is not thread safe. 23 class NetworkTimeTracker { 24 public: 25 static void RegisterPrefs(PrefRegistrySimple* registry); 26 27 NetworkTimeTracker(scoped_ptr<base::TickClock> tick_clock, 28 PrefService* pref_service); 29 ~NetworkTimeTracker(); 30 31 // Returns the network time corresponding to |time_ticks| if network time 32 // is available. Returns false if no network time is available yet. Can also 33 // return the error range if |uncertainty| isn't NULL. 34 bool GetNetworkTime(base::TimeTicks time_ticks, 35 base::Time* network_time, 36 base::TimeDelta* uncertainty) const; 37 38 // Calculates corresponding time ticks according to the given parameters. 39 // The provided |network_time| is precise at the given |resolution| and 40 // represent the time between now and up to |latency| + (now - |post_time|) 41 // ago. 42 void UpdateNetworkTime(base::Time network_time, 43 base::TimeDelta resolution, 44 base::TimeDelta latency, 45 base::TimeTicks post_time); 46 received_network_time()47 bool received_network_time() const { 48 return received_network_time_; 49 } 50 51 private: 52 // For querying current time ticks. 53 scoped_ptr<base::TickClock> tick_clock_; 54 55 PrefService* pref_service_; 56 57 // Network time based on last call to UpdateNetworkTime(). 58 base::Time network_time_; 59 60 // The estimated local time from |tick_clock| that corresponds with 61 // |network_time|. Assumes the actual network time measurement was performed 62 // midway through the latency time, and does not account for suspect/resume 63 // events since the network time was measured. 64 // See UpdateNetworkTime(..) implementation for details. 65 base::TimeTicks network_time_ticks_; 66 67 // Uncertainty of |network_time_| based on added inaccuracies/resolution. 68 // See UpdateNetworkTime(..) implementation for details. 69 base::TimeDelta network_time_uncertainty_; 70 71 base::ThreadChecker thread_checker_; 72 73 bool received_network_time_; 74 75 DISALLOW_COPY_AND_ASSIGN(NetworkTimeTracker); 76 }; 77 78 } // namespace network_time 79 80 #endif // COMPONENTS_NETWORK_TIME_NETWORK_TIME_TRACKER_H_ 81