xref: /openbsd-src/lib/libc/gen/ualarm.c (revision c2c925dec2134a12f472359f2a189e9a312dd721)

/*	$OpenBSD: ualarm.c,v 1.7 2005/08/08 08:05:34 espie Exp $ */
/*
 * Copyright (c) 1985, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

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

#define	USPS	1000000		/* # of microseconds in a second */

/*
 * Generate a SIGALRM signal in ``usecs'' microseconds.
 * If ``reload'' is non-zero, keep generating SIGALRM
 * every ``reload'' microseconds after the first signal.
 */
useconds_t
ualarm(useconds_t usecs, useconds_t reload)
{
	struct itimerval new, old;

	new.it_interval.tv_usec = reload % USPS;
	new.it_interval.tv_sec = reload / USPS;

	new.it_value.tv_usec = usecs % USPS;
	new.it_value.tv_sec = usecs / USPS;

	if (setitimer(ITIMER_REAL, &new, &old) == 0)
		return ((useconds_t)(old.it_value.tv_sec * USPS + old.it_value.tv_usec));
	/* else */
		return ((useconds_t)-1);
}