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