4.3BSD-UWisc/src/ucb/gprof/hertz.c

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/*
 * Copyright (c) 1983 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 */

#ifndef lint
static char sccsid[] = "@(#)hertz.c	5.1 (Berkeley) 6/4/85";
#endif not lint

#include <sys/time.h>

    /*
     *	discover the tick frequency of the machine
     *	if something goes wrong, we return 0, an impossible hertz.
     */
#define	HZ_WRONG	0

hertz()
{
	struct itimerval tim;

	tim.it_interval.tv_sec = 0;
	tim.it_interval.tv_usec = 1;
	tim.it_value.tv_sec = 0;
	tim.it_value.tv_usec = 0;
	setitimer(ITIMER_REAL, &tim, 0);
	setitimer(ITIMER_REAL, 0, &tim);
	if (tim.it_interval.tv_usec < 2)
		return(HZ_WRONG);
	return (1000000 / tim.it_interval.tv_usec);
}