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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 | 5 |
6 // Windows Timer Primer | 6 // Windows Timer Primer |
7 // | 7 // |
8 // A good article: http://www.ddj.com/windows/184416651 | 8 // A good article: http://www.ddj.com/windows/184416651 |
9 // A good mozilla bug: http://bugzilla.mozilla.org/show_bug.cgi?id=363258 | 9 // A good mozilla bug: http://bugzilla.mozilla.org/show_bug.cgi?id=363258 |
10 // | 10 // |
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114 bool SafeConvertToWord(int in, WORD* out) { | 114 bool SafeConvertToWord(int in, WORD* out) { |
115 base::CheckedNumeric<WORD> result = in; | 115 base::CheckedNumeric<WORD> result = in; |
116 *out = result.ValueOrDefault(std::numeric_limits<WORD>::max()); | 116 *out = result.ValueOrDefault(std::numeric_limits<WORD>::max()); |
117 return result.IsValid(); | 117 return result.IsValid(); |
118 } | 118 } |
119 | 119 |
120 } // namespace | 120 } // namespace |
121 | 121 |
122 // Time ----------------------------------------------------------------------- | 122 // Time ----------------------------------------------------------------------- |
123 | 123 |
124 // The internal representation of Time uses FILETIME, whose epoch is 1601-01-01 | |
125 // 00:00:00 UTC. ((1970-1601)*365+89)*24*60*60*1000*1000, where 89 is the | |
126 // number of leap year days between 1601 and 1970: (1970-1601)/4 excluding | |
127 // 1700, 1800, and 1900. | |
128 // static | |
129 const int64_t Time::kTimeTToMicrosecondsOffset = INT64_C(11644473600000000); | |
130 | |
131 // static | 124 // static |
132 Time Time::Now() { | 125 Time Time::Now() { |
133 if (initial_time == 0) | 126 if (initial_time == 0) |
134 InitializeClock(); | 127 InitializeClock(); |
135 | 128 |
136 // We implement time using the high-resolution timers so that we can get | 129 // We implement time using the high-resolution timers so that we can get |
137 // timeouts which are smaller than 10-15ms. If we just used | 130 // timeouts which are smaller than 10-15ms. If we just used |
138 // CurrentWallclockMicroseconds(), we'd have the less-granular timer. | 131 // CurrentWallclockMicroseconds(), we'd have the less-granular timer. |
139 // | 132 // |
140 // To make this work, we initialize the clock (initial_time) and the | 133 // To make this work, we initialize the clock (initial_time) and the |
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675 TimeTicks TimeTicks::FromQPCValue(LONGLONG qpc_value) { | 668 TimeTicks TimeTicks::FromQPCValue(LONGLONG qpc_value) { |
676 return TimeTicks() + QPCValueToTimeDelta(qpc_value); | 669 return TimeTicks() + QPCValueToTimeDelta(qpc_value); |
677 } | 670 } |
678 | 671 |
679 // TimeDelta ------------------------------------------------------------------ | 672 // TimeDelta ------------------------------------------------------------------ |
680 | 673 |
681 // static | 674 // static |
682 TimeDelta TimeDelta::FromQPCValue(LONGLONG qpc_value) { | 675 TimeDelta TimeDelta::FromQPCValue(LONGLONG qpc_value) { |
683 return QPCValueToTimeDelta(qpc_value); | 676 return QPCValueToTimeDelta(qpc_value); |
684 } | 677 } |
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