gm2-libs-iso/MemStream

DEFINITION MODULE MemStream ;

(*
    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.
*)

OpenWrite
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.
*)

OpenRead
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.
*)

Close
PROCEDURE Close (VAR cid: ChanId) ;

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

Rewrite
PROCEDURE Rewrite (cid: ChanId) ;

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

Reread
PROCEDURE Reread (cid: ChanId) ;

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

IsMem
PROCEDURE IsMem (cid: ChanId) : BOOLEAN ;

END MemStream.