projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 15637ed4 RG |
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, with or without | |
| 6 | * modification, are permitted provided that the following conditions | |
| 7 | * are met: | |
| 8 | * 1. Redistributions of source code must retain the above copyright | |
| 9 | * notice, this list of conditions and the following disclaimer. | |
| 10 | * 2. Redistributions in binary form must reproduce the above copyright | |
| 11 | * notice, this list of conditions and the following disclaimer in the | |
| 12 | * documentation and/or other materials provided with the distribution. | |
| 13 | * 3. All advertising materials mentioning features or use of this software | |
| 14 | * must display the following acknowledgement: | |
| 15 | * This product includes software developed by the University of | |
| 16 | * California, Berkeley and its contributors. | |
| 17 | * 4. Neither the name of the University nor the names of its contributors | |
| 18 | * may be used to endorse or promote products derived from this software | |
| 19 | * without specific prior written permission. | |
| 20 | * | |
| 21 | * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND | |
| 22 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
| 23 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
| 24 | * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE | |
| 25 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
| 26 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
| 27 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
| 28 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
| 29 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
| 30 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
| 31 | * SUCH DAMAGE. | |
| 32 | */ | |
| 33 | ||
| 34 | #ifndef lint | |
| 35 | static char sccsid[] = "@(#)hertz.c 5.4 (Berkeley) 6/1/90"; | |
| 36 | #endif /* not lint */ | |
| 37 | ||
| 38 | #include <sys/time.h> | |
| 39 | ||
| 40 | /* | |
| 41 | * discover the tick frequency of the machine | |
| 42 | * if something goes wrong, we return 0, an impossible hertz. | |
| 43 | */ | |
| 44 | #define HZ_WRONG 0 | |
| 45 | ||
| 46 | hertz() | |
| 47 | { | |
| 48 | struct itimerval tim; | |
| 49 | ||
| 50 | tim.it_interval.tv_sec = 0; | |
| 51 | tim.it_interval.tv_usec = 1; | |
| 52 | tim.it_value.tv_sec = 0; | |
| 53 | tim.it_value.tv_usec = 0; | |
| 54 | setitimer(ITIMER_REAL, &tim, 0); | |
| 55 | setitimer(ITIMER_REAL, 0, &tim); | |
| 56 | if (tim.it_interval.tv_usec < 2) | |
| 57 | return(HZ_WRONG); | |
| 58 | return (1000000 / tim.it_interval.tv_usec); | |
| 59 | } |