usr/src/lib/libbc/libc/gen/common/usleep.c

   1 /*
   2  * Copyright 1996 Sun Microsystems, Inc.  All rights reserved.
   3  * Use is subject to license terms.
   4  */
   5
   6 /*
   7  * Copyright (c) 1985 Regents of the University of California.
   8  * All rights reserved.  The Berkeley software License Agreement
   9  * specifies the terms and conditions for redistribution.
  10  */
  11
  12 #include <unistd.h>
  13 #include <sys/time.h>
  14 #include <signal.h>
  15
  16 #define USPS    1000000         /* number of microseconds in a second */
  17 #define TICK    (USPS / _sysconf(_SC_CLK_TCK))
  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 static void
  25 sleepx(void)
  26 {
  27
  28         ringring = 1;
  29 }
  30
  31 void
  32 usleep(unsigned n)
  33 {
  34         int omask;
  35         struct itimerval itv, oitv;
  36         struct itimerval *itp = &itv;
  37         struct sigvec vec, ovec;
  38
  39         if (n == 0)
  40                 return;
  41         timerclear(&itp->it_interval);
  42         timerclear(&itp->it_value);
  43         if (setitimer(ITIMER_REAL, itp, &oitv) < 0)
  44                 return;
  45         itp->it_value.tv_sec = n / USPS;
  46         itp->it_value.tv_usec = n % USPS;
  47         if (timerisset(&oitv.it_value)) {
  48                 if (timercmp(&oitv.it_value, &itp->it_value, >)) {
  49                         oitv.it_value.tv_sec -= itp->it_value.tv_sec;
  50                         oitv.it_value.tv_usec -= itp->it_value.tv_usec;
  51                         if (oitv.it_value.tv_usec < 0) {
  52                                 oitv.it_value.tv_usec += USPS;
  53                                 oitv.it_value.tv_sec--;
  54                         }
  55                 } else {
  56                         itp->it_value = oitv.it_value;
  57                         oitv.it_value.tv_sec = 0;
  58                         oitv.it_value.tv_usec = 2 * TICK;
  59                 }
  60         }
  61         setvec(vec, sleepx);
  62         (void) sigvec(SIGALRM, &vec, &ovec);
  63         omask = sigblock(sigmask(SIGALRM));
  64         ringring = 0;
  65         (void) setitimer(ITIMER_REAL, itp, (struct itimerval *)0);
  66         while (!ringring)
  67                 sigpause(omask &~ sigmask(SIGALRM));
  68         (void) sigvec(SIGALRM, &ovec, (struct sigvec *)0);
  69         (void) sigsetmask(omask);
  70         (void) setitimer(ITIMER_REAL, &oitv, (struct itimerval *)0);
  71 }