IMPLEMENTATION MODULE IOChan;
(* A ChanId is a C FILE* handle; all operations go through SysShim
   (which degrades a NIL handle to a safe no-op / 0C). *)

IMPORT SysShim;
FROM SYSTEM IMPORT ADDRESS;

TYPE ChanId = ADDRESS;

PROCEDURE StdInChan() : ChanId;
BEGIN
  RETURN SysShim.stdin()
END StdInChan;

PROCEDURE StdOutChan() : ChanId;
BEGIN
  RETURN SysShim.stdout()
END StdOutChan;

PROCEDURE StdErrChan() : ChanId;
BEGIN
  RETURN SysShim.stderr()
END StdErrChan;

PROCEDURE OpenRead(VAR name : ARRAY OF CHAR) : ChanId;
BEGIN
  RETURN SysShim.fopenread(name)
END OpenRead;

PROCEDURE OpenWrite(VAR name : ARRAY OF CHAR) : ChanId;
BEGIN
  RETURN SysShim.fopenwrite(name)
END OpenWrite;

PROCEDURE Close(VAR cid : ChanId);
BEGIN
  SysShim.fclose(cid);
  cid := NIL
END Close;

PROCEDURE IsOpen(cid : ChanId) : BOOLEAN;
BEGIN
  RETURN cid # NIL
END IsOpen;

PROCEDURE Handle(cid : ChanId) : ADDRESS;
BEGIN
  RETURN cid
END Handle;

PROCEDURE MakeChan(h : ADDRESS) : ChanId;
BEGIN
  RETURN h
END MakeChan;

PROCEDURE ReadChar(cid : ChanId) : CHAR;
BEGIN
  RETURN SysShim.fgetc(cid)
END ReadChar;

PROCEDURE ReadString(cid : ChanId; VAR s : ARRAY OF CHAR);
BEGIN
  IF SysShim.freadline(cid, s, HIGH(s) + 1) < 0 THEN
  END
END ReadString;

PROCEDURE ReadInt(cid : ChanId) : INTEGER;
BEGIN
  RETURN SysShim.freadint(cid)
END ReadInt;

PROCEDURE WriteChar(cid : ChanId; c : CHAR);
BEGIN
  SysShim.fputc(cid, c)
END WriteChar;

PROCEDURE WriteString(cid : ChanId; VAR s : ARRAY OF CHAR);
BEGIN
  SysShim.fputs(cid, s)
END WriteString;

PROCEDURE WriteInt(cid : ChanId; n : INTEGER);
BEGIN
  SysShim.fwriteint(cid, n)
END WriteInt;

PROCEDURE WriteLn(cid : ChanId);
BEGIN
  SysShim.fwriteln(cid)
END WriteLn;

PROCEDURE Position(cid : ChanId) : INTEGER;
BEGIN
  RETURN SysShim.ftell(cid)
END Position;

PROCEDURE Seek(cid : ChanId; pos : INTEGER) : BOOLEAN;
BEGIN
  RETURN SysShim.fseek(cid, pos)
END Seek;

PROCEDURE Rewind(cid : ChanId) : BOOLEAN;
BEGIN
  RETURN SysShim.fseek(cid, 0)
END Rewind;

END IOChan.