Sys_DoubleTime () - Condensed Windows

[Baker]

Sys_FloatTime in the Quake source release can act badly on multi-core machines and some other circumstances (overclocking?). This is a Windows-specific problem.

The result is demos running too fast or too slow.

This is the replacement for Sys_FloatTime thinned out ...

Code: Select all

#include <limits.h>      // LONG_MAX

static double   pfreq;
static BOOL      hwtimer = FALSE;

void Sys_InitDoubleTime (void)
{
   __int64   freq;

   if (QueryPerformanceFrequency ((LARGE_INTEGER *)&freq) && freq > 0)
   {
      // hardware timer available
      pfreq = (double)freq;
      hwtimer = TRUE;
   } else
   {
      // make sure the timer is high precision, otherwise NT gets 18ms resolution
      timeBeginPeriod (1);
   }
}

double Sys_DoubleTime (void)
{
   __int64      pcount;
   static   __int64   startcount;
   static   DWORD   starttime;
   static  BOOL   first = TRUE;
   DWORD   now;

   if (hwtimer)
   {
      QueryPerformanceCounter ((LARGE_INTEGER *)&pcount);
      if (first)
      {
         first = FALSE;
         startcount = pcount;
         return 0.0;
      }
      // TODO: check for wrapping
      return (pcount - startcount) / pfreq;
   }

   now = timeGetTime ();

   if (first)
   {
      first = FALSE;
      starttime = now;
      return 0.0;
   }

   if (now < starttime) // wrapped?
      return (now / 1000.0) + (LONG_MAX - starttime / 1000.0);

   if (now - starttime == 0)
      return 0.0;

   return (now - starttime) / 1000.0;
}