1 /* $OpenBSD: hertz.c,v 1.4 2003/06/03 02:56:08 millert 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. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 */ 32 33 #ifndef lint 34 #if 0 35 static char sccsid[] = "@(#)hertz.c 8.1 (Berkeley) 6/6/93"; 36 #else 37 static char rcsid[] = "$OpenBSD: hertz.c,v 1.4 2003/06/03 02:56:08 millert Exp $"; 38 #endif 39 #endif /* not lint */ 40 41 #include <sys/time.h> 42 43 /* 44 * discover the tick frequency of the machine 45 * if something goes wrong, we return 0, an impossible hertz. 46 */ 47 #define HZ_WRONG 0 48 49 int 50 hertz() 51 { 52 struct itimerval tim; 53 54 tim.it_interval.tv_sec = 0; 55 tim.it_interval.tv_usec = 1; 56 tim.it_value.tv_sec = 0; 57 tim.it_value.tv_usec = 0; 58 setitimer(ITIMER_REAL, &tim, 0); 59 setitimer(ITIMER_REAL, 0, &tim); 60 if (tim.it_interval.tv_usec < 2) 61 return(HZ_WRONG); 62 return (1000000 / tim.it_interval.tv_usec); 63 } 64