/*
 * Copyright 1996 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * Copyright (c) 1985 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */

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

#define	USPS	1000000		/* number of microseconds in a second */
#define	TICK	(USPS / _sysconf(_SC_CLK_TCK))

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

static int ringring;

static void
sleepx(void)
{

	ringring = 1;
}

void
usleep(unsigned n)
{
	int omask;
	struct itimerval itv, oitv;
	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);
}