12 QueryPerformanceFrequency(&freq_);
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13 QueryPerformanceCounter(&time_);
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16 // Author: Ryan M. Geiss
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17 // http://www.geisswerks.com/ryan/FAQS/timing.html
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18 void wait(double fps)
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21 QueryPerformanceCounter(&t);
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23 if (time_.QuadPart != 0)
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25 int ticks_to_wait = static_cast<int>(static_cast<double>(freq_.QuadPart) / fps);
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29 QueryPerformanceCounter(&t);
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31 int ticks_passed = static_cast<int>(static_cast<__int64>(t.QuadPart) - static_cast<__int64>(time_.QuadPart));
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32 int ticks_left = ticks_to_wait - ticks_passed;
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34 if (t.QuadPart < time_.QuadPart) // time wrap
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36 if (ticks_passed >= ticks_to_wait)
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41 // if > 0.002s left, do Sleep(1), which will actually sleep some
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42 // steady amount, probably 1-2 ms,
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43 // and do so in a nice way (cpu meter drops; laptop battery spared).
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44 // otherwise, do a few Sleep(0)'s, which just give up the timeslice,
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45 // but don't really save cpu or battery, but do pass a tiny
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47 if (ticks_left > static_cast<int>((freq_.QuadPart*2)/1000))
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50 for (int i = 0; i < 10; ++i)
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51 Sleep(0); // causes thread to give up its timeslice
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60 LARGE_INTEGER freq_;
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61 LARGE_INTEGER time_;
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