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

#### 4.4.2 gm2-libs-iso/ChanConsts ¶

    DEFINITION MODULE ChanConsts;

      (* Common types and values for channel open requests and results *)

    TYPE
      ChanFlags =        (* Request flags possibly given when a channel is opened *)
      ( readFlag,        (* input operations are requested/available *)
        writeFlag,       (* output operations are requested/available *)
        oldFlag,         (* a file may/must/did exist before the channel is opened *)
        textFlag,        (* text operations are requested/available *)
        rawFlag,         (* raw operations are requested/available *)
        interactiveFlag, (* interactive use is requested/applies *)
        echoFlag         (* echoing by interactive device on removal of characters from input
                            stream requested/applies *)
      );

      FlagSet = SET OF ChanFlags;

      (* Singleton values of FlagSet, to allow for example, read + write *)

    CONST
      read = FlagSet{readFlag};   (* input operations are requested/available *)
      write = FlagSet{writeFlag}; (* output operations are requested/available *)
      old = FlagSet{oldFlag};     (* a file may/must/did exist before the channel is opened *)
      text = FlagSet{textFlag};   (* text operations are requested/available *)
      raw = FlagSet{rawFlag};     (* raw operations are requested/available *)
      interactive = FlagSet{interactiveFlag}; (* interactive use is requested/applies *)
      echo = FlagSet{echoFlag};   (* echoing by interactive device on removal of characters from
                                     input stream requested/applies *)

    TYPE
      OpenResults =        (* Possible results of open requests *)
        (opened,           (* the open succeeded as requested *)
         wrongNameFormat,  (* given name is in the wrong format for the implementation *)
         wrongFlags,       (* given flags include a value that does not apply to the device *)
         tooManyOpen,      (* this device cannot support any more open channels *)
         outOfChans,       (* no more channels can be allocated *)
         wrongPermissions, (* file or directory permissions do not allow request *)
         noRoomOnDevice,   (* storage limits on the device prevent the open *)
         noSuchFile,       (* a needed file does not exist *)
         fileExists,       (* a file of the given name already exists when a new one is required *)
         wrongFileType,    (* the file is of the wrong type to support the required operations *)
         noTextOperations, (* text operations have been requested, but are not supported *)
         noRawOperations,  (* raw operations have been requested, but are not supported *)
         noMixedOperations,(* text and raw operations have been requested, but they
                              are not supported in combination *)
         alreadyOpen,      (* the source/destination is already open for operations not supported
                              in combination with the requested operations *)
         otherProblem      (* open failed for some other reason *)
        );

    END ChanConsts.