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(* Library module defined by the International Standard
Information technology - programming languages
BS ISO/IEC 10514-1:1996E Part 1: Modula-2, Base Language.
Copyright ISO/IEC (International Organization for Standardization
and International Electrotechnical Commission) 1996-2021.
It may be freely copied for the purpose of implementation (see page
707 of the Information technology - Programming languages Part 1:
Modula-2, Base Language. BS ISO/IEC 10514-1:1996). *)
DEFINITION MODULE StreamFile;
(* Independent sequential data streams *)
IMPORT IOChan, ChanConsts;
TYPE
ChanId = IOChan.ChanId;
FlagSet = ChanConsts.FlagSet;
OpenResults = ChanConsts.OpenResults;
(* Accepted singleton values of FlagSet *)
CONST
read = FlagSet{ChanConsts.readFlag}; (* input operations are requested/available *)
write = FlagSet{ChanConsts.writeFlag}; (* output operations are requested/available *)
old = FlagSet{ChanConsts.oldFlag}; (* a file may/must/did exist before the channel is
opened *)
text = FlagSet{ChanConsts.textFlag}; (* text operations are requested/available *)
raw = FlagSet{ChanConsts.rawFlag}; (* raw operations are requested/available *)
PROCEDURE Open (VAR cid: ChanId; name: ARRAY OF CHAR;
flags: FlagSet; VAR res: OpenResults);
(* Attempts to obtain and open a channel connected to a
sequential stream of the given name.
The read flag implies old; without the raw flag, text is
implied. If successful, assigns to cid the identity of
the opened channel, and 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.
*)
PROCEDURE IsStreamFile (cid: ChanId): BOOLEAN;
(* Tests if the channel identified by cid is open to a sequential stream. *)
PROCEDURE Close (VAR cid: ChanId);
(* If the channel identified by cid is not open to a sequential stream, the exception
wrongDevice is raised; otherwise closes the channel, and assigns the value identifying
the invalid channel to cid.
*)
END StreamFile.
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