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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 // Time represents an absolute point in coordinated universal time (UTC), | 5 // Time represents an absolute point in coordinated universal time (UTC), |
6 // internally represented as microseconds (s/1,000,000) since the Windows epoch | 6 // internally represented as microseconds (s/1,000,000) since the Windows epoch |
7 // (1601-01-01 00:00:00 UTC) (See http://crbug.com/14734). System-dependent | 7 // (1601-01-01 00:00:00 UTC) (See http://crbug.com/14734). System-dependent |
8 // clock interface routines are defined in time_PLATFORM.cc. | 8 // clock interface routines are defined in time_PLATFORM.cc. |
9 // | 9 // |
10 // TimeDelta represents a duration of time, internally represented in | 10 // TimeDelta represents a duration of time, internally represented in |
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632 #if defined(OS_WIN) | 632 #if defined(OS_WIN) |
633 // Get the absolute value of QPC time drift. For testing. | 633 // Get the absolute value of QPC time drift. For testing. |
634 static int64 GetQPCDriftMicroseconds(); | 634 static int64 GetQPCDriftMicroseconds(); |
635 | 635 |
636 static TimeTicks FromQPCValue(LONGLONG qpc_value); | 636 static TimeTicks FromQPCValue(LONGLONG qpc_value); |
637 | 637 |
638 // Returns true if the high resolution clock is working on this system. | 638 // Returns true if the high resolution clock is working on this system. |
639 // This is only for testing. | 639 // This is only for testing. |
640 static bool IsHighResClockWorking(); | 640 static bool IsHighResClockWorking(); |
641 | 641 |
| 642 // Enable high resolution time for TimeTicks::Now(). This function will |
| 643 // test for the availability of a working implementation of |
| 644 // QueryPerformanceCounter(). If one is not available, this function does |
| 645 // nothing and the resolution of Now() remains 1ms. Otherwise, all future |
| 646 // calls to TimeTicks::Now() will have the higher resolution provided by QPC. |
| 647 // Returns true if high resolution time was successfully enabled. |
| 648 static bool SetNowIsHighResNowIfSupported(); |
| 649 |
642 // Returns a time value that is NOT rollover protected. | 650 // Returns a time value that is NOT rollover protected. |
643 static TimeTicks UnprotectedNow(); | 651 static TimeTicks UnprotectedNow(); |
644 #endif | 652 #endif |
645 | 653 |
646 // Returns true if this object has not been initialized. | 654 // Returns true if this object has not been initialized. |
647 bool is_null() const { | 655 bool is_null() const { |
648 return ticks_ == 0; | 656 return ticks_ == 0; |
649 } | 657 } |
650 | 658 |
651 // Converts an integer value representing TimeTicks to a class. This is used | 659 // Converts an integer value representing TimeTicks to a class. This is used |
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735 #endif | 743 #endif |
736 }; | 744 }; |
737 | 745 |
738 inline TimeTicks TimeDelta::operator+(TimeTicks t) const { | 746 inline TimeTicks TimeDelta::operator+(TimeTicks t) const { |
739 return TimeTicks(t.ticks_ + delta_); | 747 return TimeTicks(t.ticks_ + delta_); |
740 } | 748 } |
741 | 749 |
742 } // namespace base | 750 } // namespace base |
743 | 751 |
744 #endif // BASE_TIME_TIME_H_ | 752 #endif // BASE_TIME_TIME_H_ |
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