1 /*
2 * Copyright (c) 1989, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * %sccs.include.redist.c%
6 */
7
8 #if defined(LIBC_SCCS) && !defined(lint)
9 static char sccsid[] = "@(#)usleep.c 8.1 (Berkeley) 06/04/93";
10 #endif /* LIBC_SCCS and not lint */
11
12 #include <sys/time.h>
13 #include <sys/signal.h>
14 #include <unistd.h>
15
16 #define TICK 10000 /* system clock resolution in microseconds */
17 #define USPS 1000000 /* number of microseconds in a second */
18
19 #define setvec(vec, a) \
20 vec.sv_handler = a; vec.sv_mask = vec.sv_onstack = 0
21
22 static int ringring;
23
24 void
usleep(useconds)25 usleep(useconds)
26 unsigned int useconds;
27 {
28 register struct itimerval *itp;
29 struct itimerval itv, oitv;
30 struct sigvec vec, ovec;
31 long omask;
32 static void sleephandler();
33
34 itp = &itv;
35 if (!useconds)
36 return;
37 timerclear(&itp->it_interval);
38 timerclear(&itp->it_value);
39 if (setitimer(ITIMER_REAL, itp, &oitv) < 0)
40 return;
41 itp->it_value.tv_sec = useconds / USPS;
42 itp->it_value.tv_usec = useconds % USPS;
43 if (timerisset(&oitv.it_value)) {
44 if (timercmp(&oitv.it_value, &itp->it_value, >)) {
45 oitv.it_value.tv_sec -= itp->it_value.tv_sec;
46 oitv.it_value.tv_usec -= itp->it_value.tv_usec;
47 if (oitv.it_value.tv_usec < 0) {
48 oitv.it_value.tv_usec += USPS;
49 oitv.it_value.tv_sec--;
50 }
51 } else {
52 itp->it_value = oitv.it_value;
53 oitv.it_value.tv_sec = 0;
54 oitv.it_value.tv_usec = 2 * TICK;
55 }
56 }
57 setvec(vec, sleephandler);
58 (void) sigvec(SIGALRM, &vec, &ovec);
59 omask = sigblock(sigmask(SIGALRM));
60 ringring = 0;
61 (void) setitimer(ITIMER_REAL, itp, (struct itimerval *)0);
62 while (!ringring)
63 sigpause(omask &~ sigmask(SIGALRM));
64 (void) sigvec(SIGALRM, &ovec, (struct sigvec *)0);
65 (void) sigsetmask(omask);
66 (void) setitimer(ITIMER_REAL, &oitv, (struct itimerval *)0);
67 }
68
69 static void
sleephandler()70 sleephandler()
71 {
72 ringring = 1;
73 }
74