gm2-libs-iso/TermFile (The GNU Modula-2 Compiler)

#### 4.4.72 gm2-libs-iso/TermFile ¶

    DEFINITION MODULE TermFile;

      (* Access to the terminal device *)

      (* Channels opened by this module are connected to a single
         terminal device; typed characters are distributed between
         channels according to the sequence of read requests.
      *)

    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 *)
      text = FlagSet{ChanConsts.textFlag};
      (* text operations are requested/available *)
      raw = FlagSet{ChanConsts.rawFlag};
      (* raw operations are requested/available *)
      echo = FlagSet{ChanConsts.echoFlag};
      (* echoing by interactive device on reading of
         characters from input stream requested/applies
      *)

    PROCEDURE Open (VAR cid: ChanId; flagset: FlagSet; VAR res: OpenResults);
      (* Attempts to obtain and open a channel connected to
         the terminal.  Without the raw flag, text is implied.
         Without the echo flag, line mode is requested,
         otherwise single character mode is requested.
         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 IsTermFile (cid: ChanId): BOOLEAN;
      (* Tests if the channel identified by cid is open to
         the terminal. *)

    PROCEDURE Close (VAR cid: ChanId);
      (* If the channel identified by cid is not open to the terminal,
         the exception wrongDevice is raised; otherwise closes the
         channel and assigns the value identifying the invalid channel
         to cid.
      *)

    END TermFile.