[SDL]high resolution timers?
Author
on this page http://www.libsdl.org/cgi/docwiki.cgi/SDL_GetTicks there is a note that says:
NOTE: On platforms with high resolution timers, you can get the number of microseconds. Will add details after further investigations.
Does anyone know anything more about this?
Use the source!
For example, SDL 1.2 on Windows appears not to use a high resolution timer (due to issues with QueryPerformanceCounter on Win2K apparently).
For example, SDL 1.2 on Windows appears not to use a high resolution timer (due to issues with QueryPerformanceCounter on Win2K apparently).
Author
well i did look through the header file SDL_timer.h but I did not find anything that talked about it.
You would have to look through the actual source code, not just the header. Here is a snippet from the win32 timer directory
As rip-off said, and you can see, they are just using timeGetTime( ) and not the high-res timer. Looking through the unix source, it looks like they try to use clock_gettime, but default to gettimeofday.
void SDL_StartTicks(void){ /* Set first ticks value */#ifdef USE_GETTICKCOUNT start = GetTickCount();#else#if 0 /* Apparently there are problems with QPC on Win2K */ if (QueryPerformanceFrequency(&hires_ticks_per_second) == TRUE) { hires_timer_available = TRUE; QueryPerformanceCounter(&hires_start_ticks); } else#endif { hires_timer_available = FALSE; timeBeginPeriod(1); /* use 1 ms timer precision */ start = timeGetTime(); }#endif}Uint32 SDL_GetTicks(void){ DWORD now, ticks;#ifndef USE_GETTICKCOUNT LARGE_INTEGER hires_now;#endif#ifdef USE_GETTICKCOUNT now = GetTickCount();#else if (hires_timer_available) { QueryPerformanceCounter(&hires_now); hires_now.QuadPart -= hires_start_ticks.QuadPart; hires_now.QuadPart *= 1000; hires_now.QuadPart /= hires_ticks_per_second.QuadPart; return (DWORD)hires_now.QuadPart; } else { now = timeGetTime(); }#endif if ( now < start ) { ticks = (TIME_WRAP_VALUE-start) + now; } else { ticks = (now - start); } return(ticks);}As rip-off said, and you can see, they are just using timeGetTime( ) and not the high-res timer. Looking through the unix source, it looks like they try to use clock_gettime, but default to gettimeofday.
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