git.sesse.net Git - casparcg/blob - common/utility/timer.h

   1 #pragma once\r
   2 \r
   3 #include <windows.h>\r
   4 \r
   5 namespace caspar {\r
   6         \r
   7 class timer\r
   8 {\r
   9 public:\r
  10         timer(double fps = 25.0) : fps_(fps)\r
  11         {\r
  12                 QueryPerformanceFrequency(&freq_);\r
  13                 time_.QuadPart = 0;\r
  14         }\r
  15 \r
  16         void wait()\r
  17         {\r
  18                 wait(fps_);\r
  19         }\r
  20 \r
  21         // Author: Ryan M. Geiss\r
  22         // http://www.geisswerks.com/ryan/FAQS/timing.html\r
  23         void wait(double fps)\r
  24         {       \r
  25                 LARGE_INTEGER t;\r
  26                 QueryPerformanceCounter(&t);\r
  27 \r
  28                 if (time_.QuadPart != 0)\r
  29                 {\r
  30                         int ticks_to_wait = static_cast<int>(static_cast<double>(freq_.QuadPart) / fps);\r
  31                         int done = 0;\r
  32                         do\r
  33                         {\r
  34                                 QueryPerformanceCounter(&t);\r
  35                                 \r
  36                                 int ticks_passed = static_cast<int>(static_cast<__int64>(t.QuadPart) - static_cast<__int64>(time_.QuadPart));\r
  37                                 int ticks_left = ticks_to_wait - ticks_passed;\r
  38 \r
  39                                 if (t.QuadPart < time_.QuadPart)    // time wrap\r
  40                                         done = 1;\r
  41                                 if (ticks_passed >= ticks_to_wait)\r
  42                                         done = 1;\r
  43                                 \r
  44                                 if (!done)\r
  45                                 {\r
  46                                         // if > 0.002s left, do Sleep(1), which will actually sleep some \r
  47                                         //   steady amount, probably 1-2 ms,\r
  48                                         //   and do so in a nice way (cpu meter drops; laptop battery spared).\r
  49                                         // otherwise, do a few Sleep(0)'s, which just give up the timeslice,\r
  50                                         //   but don't really save cpu or battery, but do pass a tiny\r
  51                                         //   amount of time.\r
  52                                         if (ticks_left > static_cast<int>((freq_.QuadPart*2)/1000))\r
  53                                                 Sleep(1);\r
  54                                         else                        \r
  55                                                 for (int i = 0; i < 10; ++i) \r
  56                                                         Sleep(0);  // causes thread to give up its timeslice\r
  57                                 }\r
  58                         }\r
  59                         while (!done);            \r
  60                 }\r
  61 \r
  62                 time_ = t;\r
  63         }\r
  64                 \r
  65 private:\r
  66         \r
  67         LARGE_INTEGER freq_;\r
  68         LARGE_INTEGER time_;\r
  69         double fps_;\r
  70 };\r
  71 \r
  72 }