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// Copyright 2014 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.
#ifndef COMPONENTS_NETWORK_TIME_NETWORK_TIME_TRACKER_H_
#define COMPONENTS_NETWORK_TIME_NETWORK_TIME_TRACKER_H_
#include "base/memory/scoped_ptr.h"
#include "base/threading/thread_checker.h"
#include "base/time/time.h"
class PrefRegistrySimple;
class PrefService;
namespace base {
class TickClock;
}
namespace network_time {
// A class that receives network time updates and can provide the network time
// for a corresponding local time. This class is not thread safe.
class NetworkTimeTracker {
public:
static void RegisterPrefs(PrefRegistrySimple* registry);
NetworkTimeTracker(scoped_ptr<base::TickClock> tick_clock,
PrefService* pref_service);
~NetworkTimeTracker();
// Returns the network time corresponding to |time_ticks| if network time
// is available. Returns false if no network time is available yet. Can also
// return the error range if |uncertainty| isn't NULL.
bool GetNetworkTime(base::TimeTicks time_ticks,
base::Time* network_time,
base::TimeDelta* uncertainty) const;
// Calculates corresponding time ticks according to the given parameters.
// The provided |network_time| is precise at the given |resolution| and
// represent the time between now and up to |latency| + (now - |post_time|)
// ago.
void UpdateNetworkTime(base::Time network_time,
base::TimeDelta resolution,
base::TimeDelta latency,
base::TimeTicks post_time);
bool received_network_time() const {
return received_network_time_;
}
private:
// For querying current time ticks.
scoped_ptr<base::TickClock> tick_clock_;
PrefService* pref_service_;
// Network time based on last call to UpdateNetworkTime().
base::Time network_time_;
// The estimated local time from |tick_clock| that corresponds with
// |network_time|. Assumes the actual network time measurement was performed
// midway through the latency time, and does not account for suspect/resume
// events since the network time was measured.
// See UpdateNetworkTime(..) implementation for details.
base::TimeTicks network_time_ticks_;
// Uncertainty of |network_time_| based on added inaccuracies/resolution.
// See UpdateNetworkTime(..) implementation for details.
base::TimeDelta network_time_uncertainty_;
base::ThreadChecker thread_checker_;
bool received_network_time_;
DISALLOW_COPY_AND_ASSIGN(NetworkTimeTracker);
};
} // namespace network_time
#endif // COMPONENTS_NETWORK_TIME_NETWORK_TIME_TRACKER_H_
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