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#### BP compatibility (partly): `Port`, `PortW` arrays

The following listing contains the interface of the Ports unit.

This unit provides access routines for the hardware ports on the IA32, as a partial replacement for BP's `Port` and `PortW` pseudo arrays.

Since port access is platform-specific, this unit cannot be used in code intended to be portable. Even on the IA32, its use can often be avoided - e.g. Linux provides a number of `ioctl` functions, and DJGPP provides some routines to achieve things that would require port access under BP. Therefore, it is recommended to avoid using this unit whenever possible.

    { Access functions for I/O ports for GPC on an IA32 platform. This
      unit is *not* portable. It works only on IA32 platforms (tested
      under Linux and DJGPP). It is provided here only to serve as a
      replacement for BP's Port and PortW pseudo arrays.

      Copyright (C) 1998-2003 Free Software Foundation, Inc.

      Author: Frank Heckenbach <frank@pascal.gnu.de>

      This file is part of GNU Pascal.

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

      GNU Pascal 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
      General Public License for more details.

      You should have received a copy of the GNU General Public License
      along with GNU Pascal; see the file COPYING. If not, write to the
      Free Software Foundation, 59 Temple Place - Suite 330, Boston, MA
      02111-1307, USA.

      As a special exception, if you link this file with files compiled
      with a GNU compiler to produce an executable, this does not cause
      the resulting executable to be covered by the GNU General Public
      License. This exception does not however invalidate any other
      reasons why the executable file might be covered by the GNU
      General Public License. }

    {$gnu-pascal,I-}
    {$if __GPC_RELEASE__ < 20030303}
    {$error This unit requires GPC release 20030303 or newer.}
    {$endif}
    {$ifndef __i386__}
    {$error The Ports unit is only for the IA32 platform}
    {$endif}

    unit Ports;

    interface

    { Port access functions }
    function  InPortB  (PortNumber: ShortWord): Byte;
    function  InPortW  (PortNumber: ShortWord): ShortWord;
    procedure OutPortB (PortNumber: ShortWord; aValue: Byte);
    procedure OutPortW (PortNumber, aValue: ShortWord);

    { libc functions for getting access to the ports -- only for root
      processes, of course -- and to give up root privileges after
      getting access to the ports for setuid root programs. Dummies
      under DJGPP. }
    {$ifdef MSDOS}
    function  IOPerm (From, Num: MedCard; On: Integer): Integer;
      attribute (name = 'ioperm');
    function  IOPL (Level: Integer): Integer; attribute (name = 'iopl');
    function  SetEUID (EUID: Integer): Integer; attribute (name
      = 'seteuid');
    {$else}
    function  IOPerm (From, Num: MedCard; On: Integer): Integer;
      external name 'ioperm';
    function  IOPL (Level: Integer): Integer; external name 'iopl';
    function  SetEUID (EUID: Integer): Integer; external name 'seteuid';
    {$endif}