(* SimpleCipher.def provides a pegalogical caesar cipher.

Copyright (C) 2008-2025 Free Software Foundation, Inc.
Contributed by Gaius Mulley <gaius.mulley@southwales.ac.uk>.

This file is part of GNU Modula-2.

GNU Modula-2 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 3, or (at your option)
any later version.

GNU Modula-2 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.

Under Section 7 of GPL version 3, you are granted additional
permissions described in the GCC Runtime Library Exception, version
3.1, as published by the Free Software Foundation.

You should have received a copy of the GNU General Public License and
a copy of the GCC Runtime Library Exception along with this program;
see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
<http://www.gnu.org/licenses/>.  *)

DEFINITION MODULE SimpleCipher ;

(*
    Title      : SimpleCipher
    Author     : Gaius Mulley
    System     : GNU Modula-2
    Date       : Mon Sep 29 11:02:56 2008
    Revision   : $Version$ 
    Description: provides a simple Caesar cipher layer which
                 can be attached to any channel device.  This,
                 pedagogical, module is designed to show how
                 it is possible to add further layers underneath
                 the channel devices.
*)

FROM IOChan IMPORT ChanId ;


(*
   InsertCipherLayer - inserts a caesar cipher below channel, cid.
                       The encryption, key, is specified.
*)

PROCEDURE InsertCipherLayer (cid: ChanId; key: INTEGER) ;


(*
   RemoveCipherLayer - removes a Caesar cipher below channel, cid.
*)

PROCEDURE RemoveCipherLayer (cid: ChanId) ;


END SimpleCipher.
