(* MemStream.def provide a memory stream channel.

Copyright (C) 2015-2023 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 MemStream ;

(*
    Title      : MemStream
    Author     : Gaius Mulley
    System     : GNU Modula-2
    Date       : Wed Jan 28 16:44:30 2015
    Revision   : $Version$
    Description: provides an ISO module which can write to a memory
                 buffer or read from a memory buffer.
*)

FROM IOChan IMPORT ChanId ;
FROM ChanConsts IMPORT FlagSet, OpenResults ;
FROM SYSTEM IMPORT ADDRESS, LOC ;


(*
   Attempts to obtain and open a channel connected to a contigeous
   buffer in memory.  The write flag is implied; without the raw
   flag, text is implied.  If successful, assigns to cid the identity of
   the opened channel, assigns the value opened to res.
   If a channel cannot be opened as required,
   the value of res indicates the reason, and cid identifies the
   invalid channel.

   The parameters, buffer, length and used maybe updated as
   data is written.  The buffer maybe reallocated
   and its address might alter, however the parameters will
   always reflect the current active buffer.  When this
   channel is closed the buffer is deallocated and
   buffer will be set to NIL, length and used will be set to
   zero.
*)

PROCEDURE OpenWrite (VAR cid: ChanId; flags: FlagSet;
                     VAR res: OpenResults;
                     VAR buffer: ADDRESS;
                     VAR length: CARDINAL;
                     VAR used: CARDINAL;
                     deallocOnClose: BOOLEAN) ;


(*
   Attempts to obtain and open a channel connected to a contigeous
   buffer in memory.  The read and old flags are implied; without
   the raw flag, text is implied.  If successful, assigns to cid the
   identity of the opened channel, assigns the value opened to res, and
   selects input mode, with the read position corresponding to the start
   of the buffer.  If a channel cannot be opened as required, the value of
   res indicates the reason, and cid identifies the invalid channel.
*)

PROCEDURE OpenRead (VAR cid: ChanId; flags: FlagSet;
                    VAR res: OpenResults;
                    buffer: ADDRESS; length: CARDINAL;
                    deallocOnClose: BOOLEAN) ;


(*
   Close - if the channel identified by cid is not open to
           a memory stream, the exception wrongDevice is
           raised; otherwise closes the channel, and assigns
           the value identifying the invalid channel to cid.
*)

PROCEDURE Close (VAR cid: ChanId) ;


(*
   Rewrite - assigns the buffer index to zero.  Subsequent
             writes will overwrite the previous buffer contents.
*)

PROCEDURE Rewrite (cid: ChanId) ;


(*
   Reread - assigns the buffer index to zero.  Subsequent
            reads will read the previous buffer contents.
*)

PROCEDURE Reread (cid: ChanId) ;


(*
   IsMem - tests if the channel identified by cid is open as
           a memory stream.
*)

PROCEDURE IsMem (cid: ChanId) : BOOLEAN ;


END MemStream.