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

/*
 * Copyright (c) 1989 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that: (1) source distributions retain this entire copyright
 * notice and comment, and (2) distributions including binaries display
 * the following acknowledgement:  ``This product includes software
 * developed by the University of California, Berkeley and its contributors''
 * in the documentation or other materials provided with the distribution
 * and in all advertising materials mentioning features or use of this
 * software. 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 ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)sleep.c     5.5 (Berkeley) 6/1/90";
#endif /* LIBC_SCCS and not lint */

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

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

static int ringring;

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

        itp = &itv;
        if (!seconds)
                return;
        timerclear(&itp->it_interval);
        timerclear(&itp->it_value);
        if (setitimer(ITIMER_REAL, itp, &oitv) < 0)
                return;
        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);
}

static void
sleephandler()
{
        ringring = 1;
}