starsleep.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

#ifndef lint
static	char	*sccsid = "@(#)starsleep.c	4.1	(ULTRIX)	11/23/87";
#endif lint

/************************************************************************
 *									*
 *			Copyright (c) 1985 by				*
 *		Digital Equipment Corporation, Maynard, MA		*
 *			All rights reserved.				*
 *									*
 *   This software is furnished under a license and may be used and	*
 *   copied  only  in accordance with the terms of such license and	*
 *   with the  inclusion  of  the  above  copyright  notice.   This	*
 *   software  or  any  other copies thereof may not be provided or	*
 *   otherwise made available to any other person.  No title to and	*
 *   ownership of the software is hereby transferred.			*
 *									*
 *   The information in this software is subject to change  without	*
 *   notice  and should not be construed as a commitment by Digital	*
 *   Equipment Corporation.						*
 *									*
 *   Digital assumes no responsibility for the use  or  reliability	*
 *   of its software on equipment which is not supplied by Digital.	*
 *									*
 ************************************************************************
/*
 * starsleep.c
 *
 * Name:	starsleep
 * Purpose:	sleep routine with microseconds added, to enable sleeping
 *		for a fraction of a second.
 * Usage:	starsleep(secs, usecs)
 * Environment:	Ultrix-32
 * Compile:	see Makefile
 * Date:	November 19, 1985
 * Author:	Al Delorey
 * Remarks:
 */

/*
 * Modification history:
 *
 * November 19, 1985 - afd
 *	Derived from Berkeley 4.2 sleep routine.
 */

#include <sys/time.h>
#include <signal.h>

#define	mask(s)	(1<<((s)-1))
#define	setvec(vec, a) \
	vec.sv_handler = a; vec.sv_mask = vec.sv_onstack = 0

static int ringring;

starsleep(n,usecs)
	unsigned n;		/* number of seconds */
	unsigned usecs;		/* usecs */
{
	int sleepx(), omask;
	struct itimerval itv, oitv;
	register struct itimerval *itp = &itv;
	struct sigvec vec, ovec;

	if (n == 0 && usecs == 0)
		return;
	timerclear(&itp->it_interval);
	timerclear(&itp->it_value);
	if (setitimer(ITIMER_REAL, itp, &oitv) < 0)
		return;
	setvec(ovec, SIG_DFL);
	omask = sigblock(0);

	/* Assign seconds and micro seconds */
	itp->it_value.tv_sec = n;
	itp->it_value.tv_usec = usecs;
	if (timerisset(&oitv.it_value)) {
		if (timercmp(&oitv.it_value, &itp->it_value, >))
			oitv.it_value.tv_sec -= itp->it_value.tv_sec;
		else {
			itp->it_value = oitv.it_value;
			/*
			 * This is a hack, but we must have time to
			 * return from the setitimer after the alarm
			 * or else it'll be restarted.  And, anyway,
			 * sleep never did anything more than this before.
			 */
			oitv.it_value.tv_sec = 1;
			oitv.it_value.tv_usec = 0;
		}
	}
	setvec(vec, sleepx);
	(void) sigvec(SIGALRM, &vec, &ovec);
	ringring = 0;
	(void) setitimer(ITIMER_REAL, itp, (struct itimerval *)0);
	while (!ringring)
		sigpause(omask &~ mask(SIGALRM));
	(void) sigvec(SIGALRM, &ovec, (struct sigvec *)0);
	(void) setitimer(ITIMER_REAL, &oitv, (struct itimerval *)0);
}

static
sleepx()
{

	ringring = 1;
}