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1 | /* |
2 | * Copyright (c) 1983 Regents of the University of California. | |
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3 | * All rights reserved. |
4 | * | |
5 | * Redistribution and use in source and binary forms are permitted | |
6 | * provided that this notice is preserved and that due credit is given | |
7 | * to the University of California at Berkeley. The name of the University | |
8 | * may not be used to endorse or promote products derived from this | |
9 | * software without specific prior written permission. This software | |
10 | * is provided ``as is'' without express or implied warranty. | |
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11 | */ |
12 | ||
551f2768 | 13 | #ifndef lint |
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14 | static char sccsid[] = "@(#)hertz.c 5.2 (Berkeley) %G%"; |
15 | #endif /* not lint */ | |
551f2768 | 16 | |
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17 | #include <sys/time.h> |
18 | ||
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19 | /* |
20 | * discover the tick frequency of the machine | |
648db063 | 21 | * if something goes wrong, we return 0, an impossible hertz. |
551f2768 | 22 | */ |
648db063 | 23 | #define HZ_WRONG 0 |
10ac51bc | 24 | |
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25 | hertz() |
26 | { | |
39bd51fe | 27 | struct itimerval tim; |
551f2768 | 28 | |
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29 | tim.it_interval.tv_sec = 0; |
30 | tim.it_interval.tv_usec = 1; | |
31 | tim.it_value.tv_sec = 0; | |
32 | tim.it_value.tv_usec = 0; | |
33 | setitimer(ITIMER_REAL, &tim, 0); | |
34 | setitimer(ITIMER_REAL, 0, &tim); | |
35 | if (tim.it_interval.tv_usec < 2) | |
36 | return(HZ_WRONG); | |
37 | return (1000000 / tim.it_interval.tv_usec); | |
551f2768 | 38 | } |