gcc/m2/gm2-libs-iso/StreamFile.def

   1 (* Library module defined by the International Standard
   2    Information technology - programming languages
   3    BS ISO/IEC 10514-1:1996E Part 1: Modula-2, Base Language.
   4
   5    Copyright ISO/IEC (International Organization for Standardization
   6    and International Electrotechnical Commission) 1996-2021.
   7
   8    It may be freely copied for the purpose of implementation (see page
   9    707 of the Information technology - Programming languages Part 1:
  10    Modula-2, Base Language.  BS ISO/IEC 10514-1:1996).  *)
  11
  12 DEFINITION MODULE StreamFile;
  13
  14   (* Independent sequential data streams *)
  15
  16 IMPORT IOChan, ChanConsts;
  17
  18 TYPE
  19   ChanId = IOChan.ChanId;
  20   FlagSet = ChanConsts.FlagSet;
  21   OpenResults = ChanConsts.OpenResults;
  22
  23   (* Accepted singleton values of FlagSet *)
  24
  25 CONST
  26   read = FlagSet{ChanConsts.readFlag};   (* input operations are requested/available *)
  27   write = FlagSet{ChanConsts.writeFlag}; (* output operations are requested/available *)
  28   old = FlagSet{ChanConsts.oldFlag};     (* a file may/must/did exist before the channel is
  29                                             opened *)
  30   text = FlagSet{ChanConsts.textFlag};   (* text operations are requested/available *)
  31   raw = FlagSet{ChanConsts.rawFlag};     (* raw operations are requested/available *)
  32
  33
  34 PROCEDURE Open (VAR cid: ChanId; name: ARRAY OF CHAR;
  35                 flags: FlagSet; VAR res: OpenResults);
  36   (* Attempts to obtain and open a channel connected to a
  37      sequential stream of the given name.
  38      The read flag implies old; without the raw flag, text is
  39      implied.  If successful, assigns to cid the identity of
  40      the opened channel, and assigns the value opened to res.
  41      If a channel cannot be opened as required, the value of
  42      res indicates the reason, and cid identifies the invalid
  43      channel.
  44   *)
  45
  46 PROCEDURE IsStreamFile (cid: ChanId): BOOLEAN;
  47   (* Tests if the channel identified by cid is open to a sequential stream. *)
  48
  49 PROCEDURE Close (VAR cid: ChanId);
  50   (* If the channel identified by cid is not open to a sequential stream, the exception
  51      wrongDevice is raised; otherwise closes the channel, and assigns the value identifying
  52      the invalid channel to cid.
  53   *)
  54
  55 END StreamFile.
  56