/* Copyright (C) 1992 Free Software Foundation, Inc.
This file is part of the GNU C Library.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
Cambridge, MA 02139, USA.  */

#include <ansidecl.h>
#include <sysdep.h>
#include <errno.h>
#include <stddef.h>
#include <signal.h>


/* If ACT is not NULL, change the action for SIG to *ACT.
   If OACT is not NULL, put the old action for SIG in *OACT.  */
int
DEFUN(__sigaction, (sig, act, oact),
      int sig AND CONST struct sigaction *act AND struct sigaction *oact)
{
  sighandler_t handler;
  int save;

  if (sig <= 0 || sig >= NSIG)
    {
      errno = EINVAL;
      return -1;
    }

  if (act == NULL)
    {
      if (oact == NULL)
	return 0;
      /* Race condition, but this is the only way to do it.  */
      handler = signal (sig, SIG_IGN);
      if (handler == SIG_ERR)
	return -1;
      save = errno;
      (void) signal (sig, handler);
      errno = save;
    }
  else
    {
      if (act->sa_flags != 0 || act->sa_mask != 0)
	{
	  errno = ENOSYS;
	  return -1;
	}

      handler = signal (sig, act->sa_handler);
      if (handler == SIG_ERR)
	return -1;
    }

  if (oact != NULL)
    {
      oact->sa_handler = handler;
      oact->sa_mask = 0;
      oact->sa_flags = 0;
    }

  return 0;
}