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

   1 /*\r
   2 * copyright (c) 2010 Sveriges Television AB <info@casparcg.com>\r
   3 *\r
   4 *  This file is part of CasparCG.\r
   5 *\r
   6 *    CasparCG is free software: you can redistribute it and/or modify\r
   7 *    it under the terms of the GNU General Public License as published by\r
   8 *    the Free Software Foundation, either version 3 of the License, or\r
   9 *    (at your option) any later version.\r
  10 *\r
  11 *    CasparCG is distributed in the hope that it will be useful,\r
  12 *    but WITHOUT ANY WARRANTY; without even the implied warranty of\r
  13 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the\r
  14 *    GNU General Public License for more details.\r
  15 \r
  16 *    You should have received a copy of the GNU General Public License\r
  17 *    along with CasparCG.  If not, see <http://www.gnu.org/licenses/>.\r
  18 *\r
  19 */\r
  20 #pragma once\r
  21 \r
  22 #define NOMINMAX\r
  23 \r
  24 #include <windows.h>\r
  25 #include <Mmsystem.h>\r
  26 \r
  27 namespace caspar {\r
  28         \r
  29 class high_prec_timer\r
  30 {\r
  31 public:\r
  32         high_prec_timer()\r
  33                 : time_(0)\r
  34         {\r
  35         }\r
  36 \r
  37         // Author: Ryan M. Geiss\r
  38         // http://www.geisswerks.com/ryan/FAQS/timing.html\r
  39         void tick(double interval)\r
  40         {       \r
  41                 auto t = ::timeGetTime();\r
  42 \r
  43                 if (time_ != 0)\r
  44                 {\r
  45                         auto ticks_to_wait = static_cast<DWORD>(interval*1000.0);\r
  46                         bool done = 0;\r
  47                         do\r
  48                         {                               \r
  49                                 auto ticks_passed = t - time_;\r
  50                                 auto ticks_left   = ticks_to_wait - ticks_passed;\r
  51 \r
  52                                 if (t < time_)    // time wrap\r
  53                                         done = 1;\r
  54                                 if (ticks_passed >= ticks_to_wait)\r
  55                                         done = 1;\r
  56                                 \r
  57                                 if (!done)\r
  58                                 {\r
  59                                         // if > 0.002s left, do Sleep(1), which will actually sleep some \r
  60                                         //   steady amount, probably 1-2 ms,\r
  61                                         //   and do so in a nice way (cpu meter drops; laptop battery spared).\r
  62                                         // otherwise, do a few Sleep(0)'s, which just give up the timeslice,\r
  63                                         //   but don't really save cpu or battery, but do pass a tiny\r
  64                                         //   amount of time.\r
  65                                         if (ticks_left > 2)\r
  66                                                 Sleep(1);\r
  67                                         else                        \r
  68                                                 for (int i = 0; i < 10; ++i) \r
  69                                                         Sleep(0);  // causes thread to give up its timeslice\r
  70                                 }\r
  71 \r
  72                                 t = ::timeGetTime();\r
  73                         }\r
  74                         while (!done);            \r
  75                 }\r
  76 \r
  77                 time_ = t;\r
  78         }               \r
  79 private:        \r
  80         DWORD time_;\r
  81 };\r
  82 \r
  83 \r
  84 }