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       ggCurTime, ggUSleep, ggUSlumber - Portable Time Routines


       #include <ggi/gg.h>

       int ggCurTime(struct timeval *tv);

       int ggUSleep(int32_t usecs);

       void ggUSlumber(int32_t usecs);


       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.


       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

       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.


       A demonstration on how to measure a framerate.

       struct timeval start, stop, diff;
       long time_of_frame = 1;
       int framerate;



       /* do something here, i.e. render and display a frame */

       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;
       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);


       gettimeofday(2), usleep(3)