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sleep.c revision 1.5.2.1 
      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 1.5.2.1 1995/05/02 19:35:15 jtc Exp $";
     37 #endif /* LIBC_SCCS and not lint */
     38 
     39 #include "namespace.h"
     40 #include <sys/time.h>
     41 #include <signal.h>
     42 #include <unistd.h>
     43 
     44 unsigned int
     45 sleep(seconds)
     46 	unsigned int seconds;
     47 {
     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 	if (!seconds)
     55 		return 0;
     56 
     57 	sigemptyset(&set);
     58 	sigaddset(&set, SIGALRM);
     59 	sigprocmask(SIG_BLOCK, &set, &oset);
     60 
     61 	act.sa_handler = sleephandler;
     62 	act.sa_flags = 0;
     63 	sigemptyset(&act.sa_mask);
     64 	sigaction(SIGALRM, &act, &oact);
     65 
     66 	timerclear(&itv.it_interval);
     67 	itv.it_value.tv_sec = seconds;
     68 	itv.it_value.tv_usec = 0;
     69 	timerclear(&diff);
     70 	setitimer(ITIMER_REAL, &itv, &oitv);
     71 
     72 	if (timerisset(&oitv.it_value)) {
     73 		if (timercmp(&oitv.it_value, &itv.it_value, >)) {
     74 			oitv.it_value.tv_sec -= itv.it_value.tv_sec;
     75 		} else {
     76 			/*
     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 			diff = itv.it_value;
     82 			__timersub(&diff, &oitv.it_value);
     83 			itv.it_value = oitv.it_value;
     84 			/*
     85 			 * This is a hack, but we must have time to return
     86 			 * from the setitimer after the alarm or else it'll
     87 			 * be restarted.  And, anyway, sleep never did
     88 			 * anything more than this before.
     89 			 */
     90 			oitv.it_value.tv_sec  = 1;
     91 			oitv.it_value.tv_usec = 0;
     92 
     93 			setitimer(ITIMER_REAL, &itv, NULL);
     94 		}
     95 	}
     96 
     97  	(void) sigsuspend (&oset);
     98 
     99 	sigaction(SIGALRM, &oact, NULL);
    100 	sigprocmask(SIG_SETMASK, &oset, NULL);
    101 
    102 	(void) setitimer(ITIMER_REAL, &oitv, &itv);
    103 
    104 	if (timerisset(&diff))
    105 		__timeradd(&itv.it_value, &diff);
    106 
    107 	return (itv.it_value.tv_sec);
    108 }
    109 
    110 static void
    111 sleephandler()
    112 {
    113 }
    114