usleep.c revision 1574 
1/*
2 * Copyright (c) 1989, 1993
3 *	The Regents of the University of California.  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)
35static char sccsid[] = "@(#)usleep.c	8.1 (Berkeley) 6/4/93";
36#endif /* LIBC_SCCS and not lint */
37
38#include <sys/time.h>
39#include <sys/signal.h>
40#include <unistd.h>
41
42#define	TICK	10000		/* system clock resolution in microseconds */
43#define	USPS	1000000		/* number of microseconds in a second */
44
45#define	setvec(vec, a) \
46	vec.sv_handler = a; vec.sv_mask = vec.sv_onstack = 0
47
48static int ringring;
49
50void
51usleep(useconds)
52	unsigned int useconds;
53{
54	register struct itimerval *itp;
55	struct itimerval itv, oitv;
56	struct sigvec vec, ovec;
57	long omask;
58	static void sleephandler();
59
60	itp = &itv;
61	if (!useconds)
62		return;
63	timerclear(&itp->it_interval);
64	timerclear(&itp->it_value);
65	if (setitimer(ITIMER_REAL, itp, &oitv) < 0)
66		return;
67	itp->it_value.tv_sec = useconds / USPS;
68	itp->it_value.tv_usec = useconds % USPS;
69	if (timerisset(&oitv.it_value)) {
70		if (timercmp(&oitv.it_value, &itp->it_value, >)) {
71			oitv.it_value.tv_sec -= itp->it_value.tv_sec;
72			oitv.it_value.tv_usec -= itp->it_value.tv_usec;
73			if (oitv.it_value.tv_usec < 0) {
74				oitv.it_value.tv_usec += USPS;
75				oitv.it_value.tv_sec--;
76			}
77		} else {
78			itp->it_value = oitv.it_value;
79			oitv.it_value.tv_sec = 0;
80			oitv.it_value.tv_usec = 2 * TICK;
81		}
82	}
83	setvec(vec, sleephandler);
84	(void) sigvec(SIGALRM, &vec, &ovec);
85	omask = sigblock(sigmask(SIGALRM));
86	ringring = 0;
87	(void) setitimer(ITIMER_REAL, itp, (struct itimerval *)0);
88	while (!ringring)
89		sigpause(omask &~ sigmask(SIGALRM));
90	(void) sigvec(SIGALRM, &ovec, (struct sigvec *)0);
91	(void) sigsetmask(omask);
92	(void) setitimer(ITIMER_REAL, &oitv, (struct itimerval *)0);
93}
94
95static void
96sleephandler()
97{
98	ringring = 1;
99}
100