IMPLEMENTATION MODULE StreamFile;
(* Open/Close map onto IOChan's OpenRead/OpenWrite.  A channel is a
   stream channel whenever it is open (V3's channels are all streams). *)

IMPORT IOChan, ChanConsts;
FROM ChanConsts IMPORT opened, noSuchFile, wrongFlags;
FROM ChanConsts IMPORT readFlag, writeFlag;

PROCEDURE HasFlag (flags : ChanConsts.FlagSet;
                   f : ChanConsts.ChanFlags) : BOOLEAN;
BEGIN
  RETURN f IN flags
END HasFlag;

PROCEDURE Open (VAR cid : ChanId; name : ARRAY OF CHAR;
                flags : FlagSet; VAR res : OpenResults);
  VAR c : ChanId;
BEGIN
  IF HasFlag(flags, readFlag) THEN
    c := IOChan.OpenRead(name);
    IF NOT IOChan.IsOpen(c) THEN
      cid := IOChan.MakeChan(NIL); res := noSuchFile; RETURN
    END
  ELSIF HasFlag(flags, writeFlag) THEN
    c := IOChan.OpenWrite(name);
    IF NOT IOChan.IsOpen(c) THEN
      cid := IOChan.MakeChan(NIL); res := noSuchFile; RETURN
    END
  ELSE
    cid := IOChan.MakeChan(NIL); res := wrongFlags; RETURN
  END;
  cid := c;
  res := opened
END Open;

PROCEDURE IsStreamFile (cid : ChanId) : BOOLEAN;
BEGIN
  RETURN IOChan.IsOpen(cid)
END IsStreamFile;

PROCEDURE Close (VAR cid : ChanId);
BEGIN
  IOChan.Close(cid)
END Close;

END StreamFile.