projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| c0bc4ef7 DF |
1 | /* |
| 2 | * Copyright (c) 1983 Regents of the University of California. | |
| 3 | * All rights reserved. The Berkeley software License Agreement | |
| 4 | * specifies the terms and conditions for redistribution. | |
| 5 | */ | |
| 6 | ||
| 551f2768 | 7 | #ifndef lint |
| c0bc4ef7 DF |
8 | static char sccsid[] = "@(#)hertz.c 5.1 (Berkeley) %G%"; |
| 9 | #endif not lint | |
| 551f2768 | 10 | |
| 39bd51fe KM |
11 | #include <sys/time.h> |
| 12 | ||
| 551f2768 PK |
13 | /* |
| 14 | * discover the tick frequency of the machine | |
| 648db063 | 15 | * if something goes wrong, we return 0, an impossible hertz. |
| 551f2768 | 16 | */ |
| 648db063 | 17 | #define HZ_WRONG 0 |
| 10ac51bc | 18 | |
| 551f2768 PK |
19 | hertz() |
| 20 | { | |
| 39bd51fe | 21 | struct itimerval tim; |
| 551f2768 | 22 | |
| 39bd51fe KM |
23 | tim.it_interval.tv_sec = 0; |
| 24 | tim.it_interval.tv_usec = 1; | |
| 25 | tim.it_value.tv_sec = 0; | |
| 26 | tim.it_value.tv_usec = 0; | |
| 27 | setitimer(ITIMER_REAL, &tim, 0); | |
| 28 | setitimer(ITIMER_REAL, 0, &tim); | |
| 29 | if (tim.it_interval.tv_usec < 2) | |
| 30 | return(HZ_WRONG); | |
| 31 | return (1000000 / tim.it_interval.tv_usec); | |
| 551f2768 | 32 | } |