Dogcows Code - chaz/yoink/blob - src/Moof/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 <cerrno>
  30 #include <ctime>
  31 #include <stdexcept>
  32
  33 #include "Timer.hh"
  34
  35 #if HAVE_CONFIG_H
  36 #include "config.h"
  37 #endif
  38
  39
  40 namespace Mf {
  41
  42
  43 #if HAVE_CLOCK_GETTIME
  44
  45 // Since the monotonic clock will provide us with the timer since the computer
  46 // started, the number of seconds since that time could easily become so large
  47 // that it cannot be accurately stored in a float (even with as little two days
  48 // uptime), therefore we need to start from a more recent reference (when the
  49 // program starts).  Of course this isn't much of an issue if scalar is a
  50 // double-precision number.
  51
  52 static time_t setReference_()
  53 {
  54         struct timespec ts;
  55
  56         if (clock_gettime(CLOCK_MONOTONIC, &ts) != 0)
  57         {
  58                 return 0;
  59         }
  60
  61         return ts.tv_sec;
  62 }
  63
  64 static const time_t reference = setReference_();
  65
  66
  67 Scalar getTicks()
  68 {
  69         struct timespec ts;
  70
  71         if (clock_gettime(CLOCK_MONOTONIC, &ts) != 0)
  72         {
  73                 throw std::runtime_error("cannot access monotonic clock");
  74         }
  75
  76         return Scalar(ts.tv_sec - reference) + Scalar(ts.tv_nsec) / 1000000000.0;
  77 }
  78
  79 void sleep(Scalar seconds, bool absolute)
  80 {
  81         struct timespec ts;
  82         int ret;
  83
  84         if (absolute) seconds -= getTicks();
  85         ts.tv_sec = time_t(seconds);
  86         ts.tv_nsec = long((seconds - Scalar(ts.tv_sec)) * 1000000000.0);
  87
  88         do
  89         {
  90                 ret = nanosleep(&ts, &ts);
  91         }
  92         while (ret == -1 && errno == EINTR);
  93 }
  94
  95
  96 #else // ! HAVE_CLOCK_GETTIME
  97
  98
  99 // If we don't have posix timers, we'll have to use a different timing method.
 100 // SDL only promises centisecond accuracy, but that's better than a kick in the
 101 // butt.
 102
 103 #include <SDL/SDL.h>
 104
 105 Scalar getTicks()
 106 {
 107         Uint32 ms = SDL_GetTicks();
 108         return Scalar(ms / 1000) + Scalar(ms % 1000) / 1000.0;
 109 }
 110
 111 void sleep(Scalar seconds, bool absolute)
 112 {
 113         if (absolute) seconds -= getTicks();
 114
 115         SDL_Delay(Uint32(seconds * 1000.0));
 116 }
 117
 118 #endif // HAVE_CLOCK_GETTIME
 119
 120
 121 } // namespace Mf
 122
 123 /** vim: set ts=4 sw=4 tw=80: *************************************************/
 124