1 /* $OpenBSD: hertz.c,v 1.3 2001/03/22 05:18:30 mickey Exp $ */ 2 /* $NetBSD: hertz.c,v 1.5 1995/04/19 07:16:03 cgd Exp $ */ 3 4 /* 5 * Copyright (c) 1983, 1993 6 * The Regents of the University of California. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37 #ifndef lint 38 #if 0 39 static char sccsid[] = "@(#)hertz.c 8.1 (Berkeley) 6/6/93"; 40 #else 41 static char rcsid[] = "$OpenBSD: hertz.c,v 1.3 2001/03/22 05:18:30 mickey Exp $"; 42 #endif 43 #endif /* not lint */ 44 45 #include <sys/time.h> 46 47 /* 48 * discover the tick frequency of the machine 49 * if something goes wrong, we return 0, an impossible hertz. 50 */ 51 #define HZ_WRONG 0 52 53 int 54 hertz() 55 { 56 struct itimerval tim; 57 58 tim.it_interval.tv_sec = 0; 59 tim.it_interval.tv_usec = 1; 60 tim.it_value.tv_sec = 0; 61 tim.it_value.tv_usec = 0; 62 setitimer(ITIMER_REAL, &tim, 0); 63 setitimer(ITIMER_REAL, 0, &tim); 64 if (tim.it_interval.tv_usec < 2) 65 return(HZ_WRONG); 66 return (1000000 / tim.it_interval.tv_usec); 67 } 68