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[unix-history] / usr / src / lib / libc / gen / usleep.c

#ifndef lint
static char sccsid[] = "@(#)usleep.c	1.1 (Berkeley) %G%";
#endif

#include <sys/time.h>
#include <signal.h>

#define USPS	1000000		/* number of microseconds in a second */
#define TICK	10000		/* system clock resolution in microseconds */

#define	setvec(vec, a) \
	vec.sv_handler = a; vec.sv_mask = vec.sv_onstack = 0

static int ringring;

usleep(n)
	unsigned n;
{
	int sleepx(), omask;
	struct itimerval itv, oitv;
	register struct itimerval *itp = &itv;
	struct sigvec vec, ovec;

	if (n == 0)
		return;
	timerclear(&itp->it_interval);
	timerclear(&itp->it_value);
	if (setitimer(ITIMER_REAL, itp, &oitv) < 0)
		return;
	itp->it_value.tv_sec = n / USPS;
	itp->it_value.tv_usec = n % USPS;
	if (timerisset(&oitv.it_value)) {
		if (timercmp(&oitv.it_value, &itp->it_value, >)) {
			oitv.it_value.tv_sec -= itp->it_value.tv_sec;
			oitv.it_value.tv_usec -= itp->it_value.tv_usec;
			if (oitv.it_value.tv_usec < 0) {
				oitv.it_value.tv_usec += USPS;
				oitv.it_value.tv_sec--;
			}
		} else {
			itp->it_value = oitv.it_value;
			oitv.it_value.tv_sec = 0;
			oitv.it_value.tv_usec = 2 * TICK;
		}
	}
	setvec(vec, sleepx);
	(void) sigvec(SIGALRM, &vec, &ovec);
	omask = sigblock(sigmask(SIGALRM));
	ringring = 0;
	(void) setitimer(ITIMER_REAL, itp, (struct itimerval *)0);
	while (!ringring)
		sigpause(omask &~ sigmask(SIGALRM));
	(void) sigvec(SIGALRM, &ovec, (struct sigvec *)0);
	(void) sigsetmask(omask);
	(void) setitimer(ITIMER_REAL, &oitv, (struct itimerval *)0);
}

static
sleepx()
{

	ringring = 1;
}