chrome/browser/network_time/network_time_tracker.h

   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
  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_