Dogcows Code - chaz/yoink/blob - src/timer.cc

   1
   2 /*******************************************************************************
   3
   4  Copyright (c) 2009, Charles McGarvey
   5  All rights reserved.
   6
   7  Redistribution   and   use  in  source  and  binary  forms,  with  or  without
   8  modification, are permitted provided that the following conditions are met:
   9
  10    * Redistributions  of  source  code  must retain the above copyright notice,
  11      this list of conditions and the following disclaimer.
  12    * Redistributions  in binary form must reproduce the above copyright notice,
  13      this  list of conditions and the following disclaimer in the documentation
  14      and/or other materials provided with the distribution.
  15
  16  THIS  SOFTWARE  IS  PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  17  AND  ANY  EXPRESS  OR  IMPLIED  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  18  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  19  DISCLAIMED.  IN  NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
  20  FOR  ANY  DIRECT,  INDIRECT,  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  21  DAMAGES  (INCLUDING,  BUT  NOT  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  22  SERVICES;  LOSS  OF  USE,  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  23  CAUSED  AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  24  OR  TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  25  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26
  27 *******************************************************************************/
  28
  29 #include <stdexcept>
  30 #include <ctime>
  31 #include <cerrno>
  32
  33 #include "timer.hh"
  34
  35
  36 namespace dc {
  37
  38
  39 #if HAVE_LIBRT
  40
  41 // Since the monotonic clock will provide us with the timer since the computer
  42 // started, the number of seconds since that time could easily become so large
  43 // that it cannot be accurately stored in a float (even with as little two days
  44 // update), therefore we need to start from a more recent reference (when the
  45 // program starts).  Of course this isn't much of an issue if scalar is a
  46 // double-precious number.
  47
  48 static time_t setReference()
  49 {
  50         struct timespec ts;
  51
  52         if (clock_gettime(CLOCK_MONOTONIC, &ts) != 0)
  53         {
  54                 return 0;
  55         }
  56
  57         return ts.tv_sec;
  58 }
  59
  60 static const time_t reference = setReference();
  61
  62
  63 scalar ticks()
  64 {
  65         struct timespec ts;
  66
  67         if (clock_gettime(CLOCK_MONOTONIC, &ts) != 0)
  68         {
  69                 throw std::runtime_error("cannot access monotonic clock");
  70         }
  71
  72         return scalar(ts.tv_sec - reference) + scalar(ts.tv_nsec) / 1000000000.0;
  73 }
  74
  75
  76 #else // ! HAVE_LIBRT
  77
  78
  79 // If we don't have librt, we'll have to use a different timing method.  SDL
  80 // only promises centisecond accuracy, but it may be better than nothing.
  81
  82 #include <SDL/SDL.h>
  83
  84 scalar ticks()
  85 {
  86         Uint32 ms = SDL_GetTicks();
  87         return scalar(ms / 1000) + scalar(ms % 1000) / 1000.0;
  88 }
  89
  90
  91 #endif // HAVE_LIBRT
  92
  93
  94 void sleep(scalar seconds, bool absolute)
  95 {
  96         struct timespec ts;
  97         int ret;
  98
  99         if (absolute) seconds -= ticks();
 100         ts.tv_sec = time_t(seconds);
 101         ts.tv_nsec = long((seconds - scalar(ts.tv_sec)) * 1000000000.0);
 102
 103         do
 104         {
 105                 ret = nanosleep(&ts, &ts);
 106         }
 107         while (ret == -1 && errno == EINTR);
 108 }
 109
 110
 111 } // namespace dc
 112
 113 /** vim: set ts=4 sw=4 tw=80: *************************************************/
 114