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sleep.c revision 1.5 
      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 1.5 1994/12/11 17:34:10 mycroft 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 	struct itimerval itv, oitv;
     48 	struct sigaction act, oact;
     49 	struct timeval diff;
     50 	sigset_t set, oset;
     51 	static void sleephandler();
     52 
     53 	if (!seconds)
     54 		return 0;
     55 
     56 	sigemptyset(&set);
     57 	sigaddset(&set, SIGALRM);
     58 	sigprocmask(SIG_BLOCK, &set, &oset);
     59 
     60 	act.sa_handler = sleephandler;
     61 	act.sa_flags = 0;
     62 	sigemptyset(&act.sa_mask);
     63 	sigaction(SIGALRM, &act, &oact);
     64 
     65 	timerclear(&itv.it_interval);
     66 	itv.it_value.tv_sec = seconds;
     67 	itv.it_value.tv_usec = 0;
     68 	timerclear(&diff);
     69 	setitimer(ITIMER_REAL, &itv, &oitv);
     70 
     71 	if (timerisset(&oitv.it_value)) {
     72 		if (timercmp(&oitv.it_value, &itv.it_value, >)) {
     73 			oitv.it_value.tv_sec -= itv.it_value.tv_sec;
     74 		} else {
     75 			/*
     76 			 * The existing timer was scheduled to fire
     77 			 * before ours, so we compute the time diff
     78 			 * so we can add it back in the end.
     79 			 */
     80 			diff = itv.it_value;
     81 			__timersub(&diff, &oitv.it_value);
     82 			itv.it_value = oitv.it_value;
     83 			/*
     84 			 * This is a hack, but we must have time to return
     85 			 * from the setitimer after the alarm or else it'll
     86 			 * be restarted.  And, anyway, sleep never did
     87 			 * anything more than this before.
     88 			 */
     89 			oitv.it_value.tv_sec  = 1;
     90 			oitv.it_value.tv_usec = 0;
     91 
     92 			setitimer(ITIMER_REAL, &itv, NULL);
     93 		}
     94 	}
     95 
     96  	(void) sigsuspend (&oset);
     97 
     98 	sigaction(SIGALRM, &oact, NULL);
     99 	sigprocmask(SIG_SETMASK, &oset, NULL);
    100 
    101 	(void) setitimer(ITIMER_REAL, &oitv, &itv);
    102 
    103 	if (timerisset(&diff))
    104 		__timeradd(&itv.it_value, &diff);
    105 
    106 	return (itv.it_value.tv_sec);
    107 }
    108 
    109 static void
    110 sleephandler()
    111 {
    112 }
    113