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usleep.c revision 1.4 
      1 /*	$NetBSD: usleep.c,v 1.4 1995/02/25 15:39:52 cgd Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 1989, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  * 3. All advertising materials mentioning features or use of this software
     16  *    must display the following acknowledgement:
     17  *	This product includes software developed by the University of
     18  *	California, Berkeley and its contributors.
     19  * 4. Neither the name of the University nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  */
     35 
     36 #if defined(LIBC_SCCS) && !defined(lint)
     37 #if 0
     38 static char sccsid[] = "@(#)usleep.c	8.1 (Berkeley) 6/4/93";
     39 #else
     40 static char rcsid[] = "$NetBSD: usleep.c,v 1.4 1995/02/25 15:39:52 cgd Exp $";
     41 #endif
     42 #endif /* LIBC_SCCS and not lint */
     43 
     44 #include <sys/time.h>
     45 #include <sys/signal.h>
     46 #include <unistd.h>
     47 
     48 #define	TICK	10000		/* system clock resolution in microseconds */
     49 #define	USPS	1000000		/* number of microseconds in a second */
     50 
     51 #define	setvec(vec, a) \
     52 	vec.sv_handler = a; vec.sv_mask = vec.sv_onstack = 0
     53 
     54 static int ringring;
     55 
     56 void
     57 usleep(useconds)
     58 	unsigned int useconds;
     59 {
     60 	register struct itimerval *itp;
     61 	struct itimerval itv, oitv;
     62 	struct sigvec vec, ovec;
     63 	long omask;
     64 	static void sleephandler();
     65 
     66 	itp = &itv;
     67 	if (!useconds)
     68 		return;
     69 	timerclear(&itp->it_interval);
     70 	timerclear(&itp->it_value);
     71 	if (setitimer(ITIMER_REAL, itp, &oitv) < 0)
     72 		return;
     73 	itp->it_value.tv_sec = useconds / USPS;
     74 	itp->it_value.tv_usec = useconds % USPS;
     75 	if (timerisset(&oitv.it_value)) {
     76 		if (timercmp(&oitv.it_value, &itp->it_value, >)) {
     77 			oitv.it_value.tv_sec -= itp->it_value.tv_sec;
     78 			oitv.it_value.tv_usec -= itp->it_value.tv_usec;
     79 			if (oitv.it_value.tv_usec < 0) {
     80 				oitv.it_value.tv_usec += USPS;
     81 				oitv.it_value.tv_sec--;
     82 			}
     83 		} else {
     84 			itp->it_value = oitv.it_value;
     85 			oitv.it_value.tv_sec = 0;
     86 			oitv.it_value.tv_usec = 2 * TICK;
     87 		}
     88 	}
     89 	setvec(vec, sleephandler);
     90 	(void) sigvec(SIGALRM, &vec, &ovec);
     91 	omask = sigblock(sigmask(SIGALRM));
     92 	ringring = 0;
     93 	(void) setitimer(ITIMER_REAL, itp, (struct itimerval *)0);
     94 	while (!ringring)
     95 		sigpause(omask &~ sigmask(SIGALRM));
     96 	(void) sigvec(SIGALRM, &ovec, (struct sigvec *)0);
     97 	(void) sigsetmask(omask);
     98 	(void) setitimer(ITIMER_REAL, &oitv, (struct itimerval *)0);
     99 }
    100 
    101 static void
    102 sleephandler()
    103 {
    104 	ringring = 1;
    105 }
    106