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.

