gnu/dist/diffutils/lib/waitpid.c

   1 /*      $NetBSD$        */
   2
   3 /* Emulate waitpid on systems that just have wait.
   4    Copyright (C) 1994, 1995, 1998, 1999 Free Software Foundation, Inc.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; see the file COPYING.
  18    If not, write to the Free Software Foundation,
  19    59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  20
  21 #if HAVE_CONFIG_H
  22 # include <config.h>
  23 #endif
  24
  25 #include <errno.h>
  26 #ifndef errno
  27 extern int errno;
  28 #endif
  29
  30 #define WAITPID_CHILDREN 8
  31 static pid_t waited_pid[WAITPID_CHILDREN];
  32 static int waited_status[WAITPID_CHILDREN];
  33
  34 pid_t
  35 waitpid (pid_t pid, int *stat_loc, int options)
  36 {
  37   int i;
  38   pid_t p;
  39
  40   if (!options && (pid == -1 || 0 < pid))
  41     {
  42       /* If we have already waited for this child, return it immediately.  */
  43       for (i = 0;  i < WAITPID_CHILDREN;  i++)
  44         {
  45           p = waited_pid[i];
  46           if (p && (p == pid || pid == -1))
  47             {
  48               waited_pid[i] = 0;
  49               goto success;
  50             }
  51         }
  52
  53       /* The child has not returned yet; wait for it, accumulating status.  */
  54       for (i = 0;  i < WAITPID_CHILDREN;  i++)
  55         if (! waited_pid[i])
  56           {
  57             p = wait (&waited_status[i]);
  58             if (p < 0)
  59               return p;
  60             if (p == pid || pid == -1)
  61               goto success;
  62             waited_pid[i] = p;
  63           }
  64     }
  65
  66   /* We cannot emulate this wait call, e.g. because of too many children.  */
  67   errno = EINVAL;
  68   return -1;
  69
  70 success:
  71   if (stat_loc)
  72     *stat_loc = waited_status[i];
  73   return p;
  74 }