DEFINITION MODULE M2makeOS;
(* OS bridge for M2make: file existence/timestamps, command execution,
   process exit, and sequential text input.
   This definition module is compiler-neutral (plain ISO Modula-2 plus
   SYSTEM.ADDRESS, available in both GNU Modula-2 and the V3 M2
   compiler).  The two implementations share no source:
     M2makeOS_gm2.mod  binds m2make_os.c via M2makeC (FOR "C"),
     M2makeOS_v3.mod   binds m2make_os.c via EXTERNAL.
   Strings are NUL-terminated buffers on both sides (V3 fixed buffers
   are NUL-padded with count == capacity), so no length bookkeeping
   crosses this boundary. *)

FROM SYSTEM IMPORT ADDRESS;

TYPE
  RdFile = ADDRESS;  (* opaque read handle; NIL when OpenRead fails *)

PROCEDURE FileExists(VAR name: ARRAY OF CHAR): BOOLEAN;
(* TRUE when name can be statted. *)

PROCEDURE FileMTime(VAR name: ARRAY OF CHAR; VAR t: LONGINT): BOOLEAN;
(* t := modification time (seconds since the epoch) of name.
   FALSE when the file cannot be statted. *)

PROCEDURE ExecCmd(VAR cmd: ARRAY OF CHAR): INTEGER;
(* Runs cmd via /bin/sh; returns the system() status (0 = success). *)

PROCEDURE ExitNow(code: INTEGER);
(* Terminates the process with the given exit code. Does not return. *)

PROCEDURE OpenRead(VAR name: ARRAY OF CHAR): RdFile;
(* Opens name for sequential text input; NIL on failure. *)

PROCEDURE ArgCount(): CARDINAL;
(* Number of command-line arguments, not counting the program name. *)

PROCEDURE GetArg(i: CARDINAL; VAR s: ARRAY OF CHAR;
                 cap: CARDINAL): BOOLEAN;
(* Copies argument i (0-based, program name excluded) into s, truncated
   to cap-1 characters plus NUL.  FALSE when there is no such
   argument or cap is 0. *)

PROCEDURE ReadLine(h: RdFile; VAR buf: ARRAY OF CHAR;
                   cap: CARDINAL): BOOLEAN;
(* Reads the next physical line (newline stripped) into buf, truncated
   to cap-1 characters plus NUL.  FALSE at end of file (a final line
   without a newline still returns TRUE once). *)

PROCEDURE CloseRead(h: RdFile);
(* Closes a handle from OpenRead (NIL is ignored). *)

END M2makeOS.