DEFINITION MODULE ChanConsts;
(* Common types and values for device open requests and results *)

(* Device modules may allow combinations of the following flags to be given
   when a channel is opened. An open procedure may not accept or honor all
   combinations. *)

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


(* Possible results of open requests: *)
TYPE
  OpenResults = (
    opened,
        (* the open succeeded as requested *)
    wrongNameFormat,
        (* given name is in the wrong format for the implementation *)
    wrongFlags,
        (* given flahs 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 binary 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.