MODULE mkdemo ;

(* Generates boot.MC4, a single-module MC64 image that prints
   "Hello MC64!" via the SYSTEM write-string service (§9.3). *)

FROM FileIO IMPORT WriteFile ;
FROM Console IMPORT Fatal ;
FROM SYSTEM IMPORT ADR ;

CONST
  HeaderSize = 64 ;
  DescDeps = 0 ;
  DescLink = 256 ;
  DescName = 264 ;
  DescLoadAddr = 280 ;
  DescChecksum = 288 ;
  DescFlags = 292 ;
  DescVarCount = 293 ;
  DescDepCount = 294 ;
  DescPad = 295 ;
  DescProcs = 296 ;
  ProcTable = 304 ;
  CodeOff = 312 ;
  FileSize = 396 ;
  StrOff = 314 ;        (* image offset of the string *)
  StrLen = 14 ;         (* 11 chars + CR + LF + NUL *)

VAR
  buf : ARRAY [0 .. FileSize - 1] OF CHAR ;
  i : CARDINAL ;
  sum : CARDINAL ;

PROCEDURE Put32 (off, v : CARDINAL) ;
BEGIN
  buf [off] := CHR (v MOD 256) ;
  buf [off + 1] := CHR ((v DIV 256) MOD 256) ;
  buf [off + 2] := CHR ((v DIV 65536) MOD 256) ;
  buf [off + 3] := CHR (v DIV 16777216) ;
END Put32 ;

PROCEDURE Put64 (off : CARDINAL; v : LONGCARD) ;
VAR j : CARDINAL ;
BEGIN
  FOR j := 0 TO 7 DO
    buf [off + j] := CHR (VAL (CARDINAL, v MOD 256)) ;
    v := v DIV 256 ;
  END ;
END Put64 ;

BEGIN
  FOR i := 0 TO FileSize - 1 DO
    buf [i] := 0C ;
  END ;

  (* file header (64 bytes) : magic *)
  buf [0] := 'M' ;
  buf [1] := 'C' ;
  buf [2] := '6' ;
  buf [3] := '4' ;

  (* descriptor *)
  buf [HeaderSize + DescName] := 'd' ;
  buf [HeaderSize + DescName + 1] := 'e' ;
  buf [HeaderSize + DescName + 2] := 'm' ;
  buf [HeaderSize + DescName + 3] := 'o' ;
  buf [HeaderSize + DescFlags] := CHR (4) ;      (* TOINIT *)
  buf [HeaderSize + DescVarCount] := CHR (0) ;
  buf [HeaderSize + DescDepCount] := CHR (0) ;
  Put64 (HeaderSize + DescProcs, 304) ;          (* proc table image offset *)

  (* procedure table : proc0 at image offset 312 *)
  Put64 (HeaderSize + ProcTable, 8) ;

  (* code : call_rel 14 ; "Hello MC64!\r\n\0" ; load_imm_byte 1 ; system ; end *)
  buf [HeaderSize + CodeOff] := CHR (8CH) ;      (* call_rel *)
  buf [HeaderSize + CodeOff + 1] := CHR (14) ;
  buf [HeaderSize + StrOff] := 'H' ;
  buf [HeaderSize + StrOff + 1] := 'e' ;
  buf [HeaderSize + StrOff + 2] := 'l' ;
  buf [HeaderSize + StrOff + 3] := 'l' ;
  buf [HeaderSize + StrOff + 4] := 'o' ;
  buf [HeaderSize + StrOff + 5] := ' ' ;
  buf [HeaderSize + StrOff + 6] := 'M' ;
  buf [HeaderSize + StrOff + 7] := 'C' ;
  buf [HeaderSize + StrOff + 8] := '6' ;
  buf [HeaderSize + StrOff + 9] := '4' ;
  buf [HeaderSize + StrOff + 10] := '!' ;
  buf [HeaderSize + StrOff + 11] := 13C ;        (* CR *)
  buf [HeaderSize + StrOff + 12] := 12C ;        (* LF *)
  buf [HeaderSize + StrOff + 13] := 0C ;         (* NUL *)
  buf [HeaderSize + CodeOff + 16] := CHR (8DH) ; (* load_imm_byte *)
  buf [HeaderSize + CodeOff + 17] := CHR (1) ;
  buf [HeaderSize + CodeOff + 18] := CHR (0C3H) ; (* system *)
  buf [HeaderSize + CodeOff + 19] := CHR (50H) ;  (* end_program *)

  (* checksum over the image, excluding the checksum field itself *)
  sum := 0 ;
  FOR i := HeaderSize TO FileSize - 1 DO
    IF NOT ((i >= 352) AND (i <= 355)) THEN
      sum := sum + ORD (buf [i]) ;
    END ;
  END ;
  Put32 (HeaderSize + DescChecksum, sum) ;

  IF NOT WriteFile ("boot.MC4", buf, FileSize) THEN
    Fatal ("mkdemo: cannot write boot.MC4") ;
  END ;
END mkdemo.