DEFINITION MODULE SysShim;
(* Low-level bridge from V3 Modula-2 to the C runtime shim
   (runtime/syslib/shim.c). Descriptor-aware: ARRAY OF CHAR is
   passed as its descriptor address, matching V3's string layout.
   This is the self-hosted counterpart of the host FileIO. *)

FROM SYSTEM IMPORT ADDRESS;

PROCEDURE fopenread (VAR name : ARRAY OF CHAR) : ADDRESS;
(* Opens name for reading; NIL on failure. *)
PROCEDURE fopenwrite (VAR name : ARRAY OF CHAR) : ADDRESS;
(* Creates/truncates name for writing; NIL on failure. *)
PROCEDURE fclose (h : ADDRESS);

PROCEDURE fread (h : ADDRESS; VAR buf : ARRAY OF CHAR;
                 max : CARDINAL) : CARDINAL;
(* Reads up to max bytes into buf; buf's length is set to the
   number read, which is also returned. *)

PROCEDURE freadline (h : ADDRESS; VAR buf : ARRAY OF CHAR;
                     max : CARDINAL) : CARDINAL;
(* Reads one line (the newline is dropped) into buf; buf's length is
   set to the number of bytes stored, which is also returned. *)
PROCEDURE fputc (h : ADDRESS; c : CHAR);
PROCEDURE fputs (h : ADDRESS; VAR s : ARRAY OF CHAR);
PROCEDURE fwriteln (h : ADDRESS);
PROCEDURE fwriteintw (h : ADDRESS; v : INTEGER; wid : CARDINAL);

PROCEDURE stdin () : ADDRESS;
PROCEDURE stdout () : ADDRESS;
PROCEDURE stderr () : ADDRESS;

PROCEDURE ftell (h : ADDRESS) : INTEGER;
(* Byte offset of the current position (-1 on error). *)
PROCEDURE fseek (h : ADDRESS; pos : INTEGER) : BOOLEAN;
(* Seek to absolute byte offset pos; FALSE on failure. *)

PROCEDURE fgetc (h : ADDRESS) : CHAR;
(* Reads one byte from h; 0C at end of file. *)
PROCEDURE freadint (h : ADDRESS) : INTEGER;
(* Reads a signed decimal integer from h, skipping leading blanks. *)
PROCEDURE fwriteint (h : ADDRESS; v : INTEGER);
(* Writes v in decimal to h (no field width). *)

PROCEDURE argc () : CARDINAL;
(* Number of command-line words, including the program name. *)

PROCEDURE arg (i : CARDINAL; VAR s : ARRAY OF CHAR;
               cap : CARDINAL) : BOOLEAN;
(* Copies command-line argument i into s (capacity cap); FALSE when
   no such argument. *)

END SysShim.