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1 // Copyright 2006-2009 Google Inc. | |
2 // | |
3 // Licensed under the Apache License, Version 2.0 (the "License"); | |
4 // you may not use this file except in compliance with the License. | |
5 // You may obtain a copy of the License at | |
6 // | |
7 // http://www.apache.org/licenses/LICENSE-2.0 | |
8 // | |
9 // Unless required by applicable law or agreed to in writing, software | |
10 // distributed under the License is distributed on an "AS IS" BASIS, | |
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
12 // See the License for the specific language governing permissions and | |
13 // limitations under the License. | |
14 // ======================================================================== | |
15 #include "omaha/base/highres_timer-win32.h" | |
16 | |
17 namespace omaha { | |
18 | |
19 bool HighresTimer::perf_freq_collected_ = false; | |
20 ULONGLONG HighresTimer::perf_freq_ = 0; | |
21 | |
22 ULONGLONG HighresTimer::GetElapsedMs() const { | |
23 ULONGLONG end_time = GetCurrentTicks(); | |
24 | |
25 // Scale to ms and round to nearerst ms - rounding is important | |
26 // because otherwise the truncation error may accumulate e.g. in sums. | |
27 // | |
28 // Given infinite resolution, this expression could be written as: | |
29 // trunc((end - start (units:freq*sec))/freq (units:sec) * | |
30 // 1000 (unit:ms) + 1/2 (unit:ms)) | |
31 ULONGLONG freq = GetTimerFrequency(); | |
32 return ((end_time - start_ticks_) * 1000L + freq / 2) / freq; | |
33 } | |
34 | |
35 ULONGLONG HighresTimer::GetElapsedSec() const { | |
36 ULONGLONG end_time = GetCurrentTicks(); | |
37 | |
38 // Scale to ms and round to nearerst ms - rounding is important | |
39 // because otherwise the truncation error may accumulate e.g. in sums. | |
40 // | |
41 // Given infinite resolution, this expression could be written as: | |
42 // trunc((end - start (units:freq*sec))/freq (unit:sec) + 1/2 (unit:sec)) | |
43 ULONGLONG freq = GetTimerFrequency(); | |
44 return ((end_time - start_ticks_) + freq / 2) / freq; | |
45 } | |
46 | |
47 void HighresTimer::CollectPerfFreq() { | |
48 LARGE_INTEGER freq; | |
49 | |
50 // Note that this is racy. | |
51 // It's OK, however, because even concurrent executions of this | |
52 // are idempotent. | |
53 if (::QueryPerformanceFrequency(&freq)) { | |
54 perf_freq_ = freq.QuadPart; | |
55 perf_freq_collected_ = true; | |
56 } | |
57 } | |
58 | |
59 } // namespace omaha | |
60 | |
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