listati/sleep.c

   1 void alarm_hand(int);
   2 unsigned int sleep(unsigned int seconds)
   3 {
   4     struct sigaction new_action, old_action;
   5     sigset_t old_mask, stop_mask, sleep_mask;
   6     /* set the signal handler */
   7     sigemptyset(&new_action.sa_mask);              /* no signal blocked */
   8     new_action.sa_handler = alarm_hand;            /* set handler */
   9     new_action.sa_flags = 0;                       /* no flags */
  10     sigaction(SIGALRM, &new_action, &old_action);  /* install action */
  11     /* block SIGALRM to avoid race conditions */
  12     sigemptyset(&stop_mask);                       /* init mask to empty */
  13     sigaddset(&stop_mask, SIGALRM);                /* add SIGALRM */
  14     sigprocmask(SIG_BLOCK, &stop_mask, &old_mask); /* add SIGALRM to blocked */
  15     /* send the alarm */
  16     alarm(seconds);
  17     /* going to sleep enabling SIGALRM */
  18     sleep_mask = old_mask;                         /* take mask */
  19     sigdelset(&sleep_mask, SIGALRM);               /* remove SIGALRM */
  20     sigsuspend(&sleep_mask);                       /* go to sleep */
  21     /* restore previous settings */
  22     sigprocmask(SIG_SETMASK, &old_mask, NULL);     /* reset signal mask */
  23     sigaction(SIGALRM, &old_action, NULL);         /* reset signal action */
  24     /* return remaining time */
  25     return alarm(0);
  26 }
  27 void alarm_hand(int sig)
  28 {
  29     return;     /* just return to interrupt sigsuspend */
  30 }