4.3BSD-Reno/src/pgrm/gprof/hertz.c

/*
 * Copyright (c) 1983 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that: (1) source distributions retain this entire copyright
 * notice and comment, and (2) distributions including binaries display
 * the following acknowledgement:  ``This product includes software
 * developed by the University of California, Berkeley and its contributors''
 * in the documentation or other materials provided with the distribution
 * and in all advertising materials mentioning features or use of this
 * software. Neither the name of the University nor the names of its
 * contributors may be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#ifndef lint
static char sccsid[] = "@(#)hertz.c	5.4 (Berkeley) 6/1/90";
#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);
}