usr/src/lib/libc/gen/sleep.c

/*
 * Copyright (c) 1989, 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)sleep.c     8.1 (Berkeley) 6/4/93";
#endif /* LIBC_SCCS and not lint */

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

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

static int ringring;

unsigned int
sleep(seconds)
        unsigned int seconds;
{
        register struct itimerval *itp;
        struct itimerval itv, oitv;
        struct sigvec vec, ovec;
        long omask;
        static void sleephandler();

        itp = &itv;
        if (!seconds)
                return 0;
        timerclear(&itp->it_interval);
        timerclear(&itp->it_value);
        if (setitimer(ITIMER_REAL, itp, &oitv) < 0)
                return seconds;
        itp->it_value.tv_sec = seconds;
        if (timerisset(&oitv.it_value)) {
                if (timercmp(&oitv.it_value, &itp->it_value, >))
                        oitv.it_value.tv_sec -= itp->it_value.tv_sec;
                else {
                        itp->it_value = oitv.it_value;
                        /*
                         * This is a hack, but we must have time to return
                         * from the setitimer after the alarm or else it'll
                         * be restarted.  And, anyway, sleep never did
                         * anything more than this before.
                         */
                        oitv.it_value.tv_sec = 1;
                        oitv.it_value.tv_usec = 0;
                }
        }
        setvec(vec, sleephandler);
        (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);
        return 0;
}

static void
sleephandler()
{
        ringring = 1;
}