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sleep.c revision 1.4 
      1 /*
      2  * Copyright (c) 1989 The Regents of the University of California.
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  * 1. Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  * 2. Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in the
     12  *    documentation and/or other materials provided with the distribution.
     13  * 3. All advertising materials mentioning features or use of this software
     14  *    must display the following acknowledgement:
     15  *	This product includes software developed by the University of
     16  *	California, Berkeley and its contributors.
     17  * 4. Neither the name of the University nor the names of its contributors
     18  *    may be used to endorse or promote products derived from this software
     19  *    without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     31  * SUCH DAMAGE.
     32  */
     33 
     34 #if defined(LIBC_SCCS) && !defined(lint)
     35 /*static char *sccsid = "from: @(#)sleep.c	5.6 (Berkeley) 2/23/91";*/
     36 static char *rcsid = "$Id: sleep.c,v 1.4 1994/05/28 06:25:04 jtc Exp $";
     37 #endif /* LIBC_SCCS and not lint */
     38 
     39 #include <sys/time.h>
     40 #include <signal.h>
     41 #include <unistd.h>
     42 
     43 unsigned int
     44 sleep(seconds)
     45 	unsigned int seconds;
     46 {
     47 	register struct itimerval *itp;
     48 	struct itimerval itv, oitv;
     49 	struct sigaction act, oact;
     50 	struct timeval diff;
     51 	sigset_t set, oset;
     52 	static void sleephandler();
     53 
     54 	itp = &itv;
     55 	if (!seconds)
     56 		return 0;
     57 
     58 	sigemptyset (&set);
     59 	sigaddset (&set, SIGALRM);
     60 	sigprocmask(SIG_BLOCK, &set, &oset);
     61 
     62 	act.sa_handler = sleephandler;
     63 	act.sa_flags   = 0;
     64 	sigemptyset(&act.sa_mask);
     65 	sigaction(SIGALRM, &act, &oact);
     66 
     67 	timerclear(&itp->it_interval);
     68 	itp->it_value.tv_sec = seconds;
     69 	itp->it_value.tv_usec = 0;
     70 	diff.tv_sec = diff.tv_usec = 0;
     71 	setitimer(ITIMER_REAL, itp, &oitv);
     72 
     73 	if (timerisset(&oitv.it_value)) {
     74 		if (timercmp(&oitv.it_value, &itp->it_value, >)) {
     75 			oitv.it_value.tv_sec -= itv.it_value.tv_sec;
     76 		} else {
     77 			/* The existing timer was scheduled to fire
     78 			   before ours, so we compute the time diff
     79 			   so we can add it back in the end. */
     80 
     81 			itp->it_value.tv_sec  -= oitv.it_value.tv_sec;
     82 			itp->it_value.tv_usec -= oitv.it_value.tv_usec;
     83 			if (itp->it_value.tv_usec < 0) {
     84 				itp->it_value.tv_sec--;
     85 				itp->it_value.tv_usec += 1000000;
     86 			}
     87 			diff = itp->it_value;
     88 
     89 			itp->it_value = oitv.it_value;
     90 			/*
     91 			 * This is a hack, but we must have time to return
     92 			 * from the setitimer after the alarm or else it'll
     93 			 * be restarted.  And, anyway, sleep never did
     94 			 * anything more than this before.
     95 			 */
     96 			oitv.it_value.tv_sec  = 1;
     97 			oitv.it_value.tv_usec = 0;
     98 
     99 			setitimer(ITIMER_REAL, &itv, NULL);
    100 		}
    101 	}
    102 
    103  	(void) sigsuspend (&oset);
    104 
    105 	sigaction(SIGALRM, &oact, NULL);
    106 	sigprocmask(SIG_SETMASK, &oset, NULL);
    107 
    108 	(void) setitimer(ITIMER_REAL, &oitv, itp);
    109 
    110 	if (diff.tv_sec != 0 || diff.tv_usec != 0) {
    111 		itp->it_value.tv_sec  += diff.tv_sec;
    112 		itp->it_value.tv_usec += diff.tv_usec;
    113 		if (itp->it_value.tv_usec > 1000000) {
    114 			itp->it_value.tv_usec -= 1000000;
    115 			itp->it_value.tv_sec++;
    116 		}
    117 	}
    118 
    119 	return (itp->it_value.tv_sec);
    120 }
    121 
    122 static void
    123 sleephandler()
    124 {
    125 }
    126