IMPLEMENTATION MODULE Files;
(* Layered on IOChan: a File holds a channel handle (a C FILE
   pointer), exposed as ADDRESS.  No direct shim binding here. *)

FROM SYSTEM IMPORT ADDRESS;

IMPORT IOChan;

TYPE
  FileRec = RECORD
    cid : IOChan.ChanId;
  END;

PROCEDURE OpenRead(VAR name : ARRAY OF CHAR) : File;
  VAR f : File;
BEGIN
  NEW(f);
  f^.cid := IOChan.OpenRead(name);
  RETURN f
END OpenRead;

PROCEDURE OpenWrite(VAR name : ARRAY OF CHAR) : File;
  VAR f : File;
BEGIN
  NEW(f);
  f^.cid := IOChan.OpenWrite(name);
  RETURN f
END OpenWrite;

PROCEDURE Close(f : File);
BEGIN
  IF f # NIL THEN
    IOChan.Close(f^.cid);
    DISPOSE(f)
  END
END Close;

PROCEDURE ReadChar(f : File) : CHAR;
BEGIN
  IF f = NIL THEN RETURN CHR(0) END;
  RETURN IOChan.ReadChar(f^.cid)
END ReadChar;

PROCEDURE ReadString(f : File; VAR s : ARRAY OF CHAR);
BEGIN
  IF f # NIL THEN IOChan.ReadString(f^.cid, s) END
END ReadString;

PROCEDURE ReadInt(f : File) : INTEGER;
BEGIN
  IF f = NIL THEN RETURN 0 END;
  RETURN IOChan.ReadInt(f^.cid)
END ReadInt;

PROCEDURE WriteChar(f : File; c : CHAR);
BEGIN
  IF f # NIL THEN IOChan.WriteChar(f^.cid, c) END
END WriteChar;

PROCEDURE WriteInt(f : File; n : INTEGER);
BEGIN
  IF f # NIL THEN IOChan.WriteInt(f^.cid, n) END
END WriteInt;

PROCEDURE WriteString(f : File; VAR s : ARRAY OF CHAR);
BEGIN
  IF f # NIL THEN IOChan.WriteString(f^.cid, s) END
END WriteString;

PROCEDURE WriteLn(f : File);
BEGIN
  IF f # NIL THEN IOChan.WriteLn(f^.cid) END
END WriteLn;

END Files.