2.11BSD#431 - /usr/src/lib/libc/gen/sleep.c

   1: /*
   2:  * Program: sleep.c
   3:  * Copyright: 1997, sms
   4:  * Author: Steven M. Schultz
   5:  *
   6:  * Version   Date	Modification
   7:  *     1.0  1997/9/25	1. Initial release.
   8: */
   9: 
  10: #include <stdio.h>  /* For NULL */
  11: #include <sys/types.h>
  12: #include <sys/time.h>
  13: 
  14: /*
  15:  * This implements the sleep(3) function using only 3 system calls instead of
  16:  * the 9 that the old implementation required.  Also this version avoids using
  17:  * signals (with the attendant system overhead) and returns the amount of
  18:  * time left unslept if an interrupt occurs.
  19:  *
  20:  * The error status of gettimeofday is not checked because if that fails the
  21:  * program has scrambled the stack so badly that a sleep() failure is the least
  22:  * problem the program has.  The select() call either completes successfully
  23:  * or is interrupted - no errors to be checked for.
  24: */
  25: 
  26: u_int
  27: sleep(seconds)
  28:     u_int seconds;
  29:     {
  30:     struct timeval f, s;
  31: 
  32:     if  (seconds)
  33:         {
  34:         gettimeofday(&f, NULL);
  35:         s.tv_sec = seconds;
  36:         s.tv_usec = 0;
  37:         select(0, NULL, NULL, NULL, &s);
  38:         gettimeofday(&s, NULL);
  39:         seconds -= (s.tv_sec - f.tv_sec);
  40: /*
  41:  * ONLY way this can happen is if the system time gets set back while we're
  42:  * in the select() call.  In this case return 0 instead of a bogus number.
  43: */
  44:         if  (seconds < 0)
  45:             seconds = 0;
  46:         }
  47:     return(seconds);
  48:     }

Defined functions