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b8f253e8 KM |
1 | /* |
2 | * Copyright (c) 1985 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 | ||
c75c7775 | 7 | #ifndef lint |
b8f253e8 KM |
8 | static char sccsid[] = "@(#)usleep.c 5.1 (Berkeley) %G%"; |
9 | #endif not lint | |
c75c7775 S |
10 | |
11 | #include <sys/time.h> | |
12 | #include <signal.h> | |
13 | ||
14 | #define USPS 1000000 /* number of microseconds in a second */ | |
15 | #define TICK 10000 /* system clock resolution in microseconds */ | |
16 | ||
17 | #define setvec(vec, a) \ | |
18 | vec.sv_handler = a; vec.sv_mask = vec.sv_onstack = 0 | |
19 | ||
20 | static int ringring; | |
21 | ||
22 | usleep(n) | |
23 | unsigned n; | |
24 | { | |
25 | int sleepx(), omask; | |
26 | struct itimerval itv, oitv; | |
27 | register struct itimerval *itp = &itv; | |
28 | struct sigvec vec, ovec; | |
29 | ||
30 | if (n == 0) | |
31 | return; | |
32 | timerclear(&itp->it_interval); | |
33 | timerclear(&itp->it_value); | |
34 | if (setitimer(ITIMER_REAL, itp, &oitv) < 0) | |
35 | return; | |
36 | itp->it_value.tv_sec = n / USPS; | |
37 | itp->it_value.tv_usec = n % USPS; | |
38 | if (timerisset(&oitv.it_value)) { | |
39 | if (timercmp(&oitv.it_value, &itp->it_value, >)) { | |
40 | oitv.it_value.tv_sec -= itp->it_value.tv_sec; | |
41 | oitv.it_value.tv_usec -= itp->it_value.tv_usec; | |
42 | if (oitv.it_value.tv_usec < 0) { | |
43 | oitv.it_value.tv_usec += USPS; | |
44 | oitv.it_value.tv_sec--; | |
45 | } | |
46 | } else { | |
47 | itp->it_value = oitv.it_value; | |
48 | oitv.it_value.tv_sec = 0; | |
49 | oitv.it_value.tv_usec = 2 * TICK; | |
50 | } | |
51 | } | |
52 | setvec(vec, sleepx); | |
53 | (void) sigvec(SIGALRM, &vec, &ovec); | |
54 | omask = sigblock(sigmask(SIGALRM)); | |
55 | ringring = 0; | |
56 | (void) setitimer(ITIMER_REAL, itp, (struct itimerval *)0); | |
57 | while (!ringring) | |
58 | sigpause(omask &~ sigmask(SIGALRM)); | |
59 | (void) sigvec(SIGALRM, &ovec, (struct sigvec *)0); | |
60 | (void) sigsetmask(omask); | |
61 | (void) setitimer(ITIMER_REAL, &oitv, (struct itimerval *)0); | |
62 | } | |
63 | ||
64 | static | |
65 | sleepx() | |
66 | { | |
67 | ||
68 | ringring = 1; | |
69 | } |