NAME¶
ggCurTime,
ggUSleep,
ggUSlumber - Portable Time Routines
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);
SEE ALSO¶
gettimeofday(2),
usleep(3)