SYNOPSIS

#include <ggi/gg.h>
int ggCurTime(struct timeval *tv);
int ggUSleep(int32_t usecs);
void ggUSlumber(int32_t usecs);

DESCRIPTION

ggCurTime fills the timeval structure pointed to by tv with the current time to the best precision available on the executing platform.

ggUSleep sleeps for at least usecs microseconds, to the best precision available on the executing platform, but may be woken up by a signal or other unspecified condition. It is not guaranteed that ggUSleep will wake up prematurely for any specific reason. It is mainly useful for points where the main objective is to avoid using CPU resources, not to perform accurate timing.

ggUSlumber does the same thing as ggUSleep, but is guaranteed not to return until the allotted time has elapsed. It is slightly less efficient than ggUSleep with reguard to CPU utilization.

All times represent wall-clock (real, versus processor) times.

The above routines are often simple macros rather than functions, and as such should not be used by reference.

The above functions are threadsafe, but are not guaranteed to be safe to use in a thread that may be cancelled during their execution. They are also not guaranteed to be safe to use in special contexts such as LibGG task handlers, signal handlers and asyncronous procedure calls.

RETURN VALUE

ggCurTime returns GGI_OK on success, or a negative value on failure. On Windows, this function will never report a failure. On platforms where gettimeofday(2) is used, the error code is the one returned by gettimeofday.

ggUSleep returns GGI_OK when the alloted time interval has elapsed, or a non-zero value if the sleep was interrupted. On platforms where usleep(3) is used, the error code is the one return by usleep.

EXAMPLE

A demonstration on how to measure a framerate.

struct timeval start, stop, diff;
long time_of_frame = 1;
int framerate;
...
ggCurTime(&start);
/* do something here, i.e. render and display a frame */
ggCurTime(&stop);
diff.tv_sec = stop_tv.tv_sec - start_tv.tv_sec;
diff.tv_usec = stop_tv.tv_usec - start_tv.tv_usec;
if (diff.tv_usec < 0) {
        diff.tv_usec += 1000000;
        diff.tv_sec--;
}
time_of_frame = diff.tv_sec * 1000 + diff.tv_usec / 1000;
if (time_of_frame == 0)
        time_of_frame = 1;      /* CPU too fast? */
printf("framerate: %i\n", 1000 / time_of_framerate);