1 /* 2 * Copyright (c) 1983 Regents of the University of California. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms are permitted 6 * provided that the above copyright notice and this paragraph are 7 * duplicated in all such forms and that any documentation, 8 * advertising materials, and other materials related to such 9 * distribution and use acknowledge that the software was developed 10 * by the University of California, Berkeley. The name of the 11 * University may not be used to endorse or promote products derived 12 * from this software without specific prior written permission. 13 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR 14 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED 15 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. 16 */ 17 18 #ifndef lint 19 static char sccsid[] = "@(#)hertz.c 5.3 (Berkeley) 06/29/88"; 20 #endif /* not lint */ 21 22 #include <sys/time.h> 23 24 /* 25 * discover the tick frequency of the machine 26 * if something goes wrong, we return 0, an impossible hertz. 27 */ 28 #define HZ_WRONG 0 29 30 hertz() 31 { 32 struct itimerval tim; 33 34 tim.it_interval.tv_sec = 0; 35 tim.it_interval.tv_usec = 1; 36 tim.it_value.tv_sec = 0; 37 tim.it_value.tv_usec = 0; 38 setitimer(ITIMER_REAL, &tim, 0); 39 setitimer(ITIMER_REAL, 0, &tim); 40 if (tim.it_interval.tv_usec < 2) 41 return(HZ_WRONG); 42 return (1000000 / tim.it_interval.tv_usec); 43 } 44