Passing Integers Between QuickBASIC and MPW Pascal 3.00 (57350)

MORE INFORMATION

When doing interlanguage calling with Microsoft QuickBASIC, the other language can make calls to the BASIC run time to get the address of passed arguments. This is accomplished with the GetNextLibArg statement.

GetNextLibArg returns a pointer to a variant record containing another pointer to each possible type of QuickBASIC variable (single precision, double precision, integer, etc.). Usually a double indirection of pointers is used to get the actual passed data.

Using double indirection of pointers with Apple MPW (Macintosh Programmer's Workshop) Pascal, however, does not return the correct value. This is a QuickBASIC header file problem. The routine below demonstrates how an inline assembly-language routine can be used in place of the double indirection to work around the problem.

More information on interlanguage calling with Microsoft QuickBASIC can be found in the "Microsoft QuickBASIC for Apple Macintosh: Language Reference," starting on page 444.

Compile and link SumIntArgs.p from Apple MPW Pascal version 3.00 as follows: Note: The file BasicLib.a.o comes with Microsoft QuickBASIC for the Apple Macintosh on the Examples disk in the User Libraries:MBPC Rsrcs:MPWP PCR Folder.

Once SumIntArgs is compiled and linked, ResEdit should be used to change parameters in SumIntArgs as follows:

1. In ResEdit, find the newly created file SumIntArgs and click once on the name so that it is highlighted.
2. While holding down the COMMAND key, press the "I" key. This is the same as choosing Get Info from the File menu. Change the following in the dialog box that appears:
   
   
   1. Change the File field to "SumIntArgs".
   2. Change the Type field to "MBPC".
   3. Change the Creator field to "MSBB".
3. Close the dialog box and click Yes when asked if you want to save.
4. Double-click SumIntArgs to open it. There should be one resource of MBPC displayed; double-click this also. Single-click the displayed MBPC and press COMMAND+I. In the Get Info dialog box that is brought up, change the Name field to SumIntArgs.

SumIntArgs is now a pure code resource that can be used with the SumInt QuickBASIC program.

Code Example

The following QuickBASIC program is SumInt, which invokes an Apple MPW Pascal routine to sum a series of passed integers:

   DEFINT a-z
   LIBRARY "SumIntArgs"

   a = 0     ' Initialize passed values
   b = 2
   c = 4
   d = 8
   CALL PrintIntArgs(a, b, c, d)        ' CALL Pascal routine
   PRINT "Sum of: "  b;" ";c;" and ";d  ' Display returned
                                        ' values
   PRINT "Is: "a
   WHILE INKEY$ = "" : WEND             ' Wait for keypress
				

The following Apple MPW Pascal routine is SumIntArgs.p, which accepts a series of passed integers from a Microsoft QuickBASIC program and returns the sum of the integers:

{**************************************************************}
{ * IntSum.p (c) 1989 Microsoft Corporation                   *}
{**************************************************************}
{ * Description:  Example to show how to pass integers from   *}
{ *               QuickBASIC to MPW Pascal and back.          *}
{**************************************************************}
{$R-}     { Turn off range checking}
unit IntSum;

interface

{*======================== INCLUDE FILES
======================*}
   uses
   {$U MemTypes.p }
      MemTypes,
   {$U BasicLibMPWP.p }
   {$U BasicLibMPWP.p }
      BasicLib;

   procedure AssignInt (ptr: LIBARGPTR; val: INT16);
   inline
      $3e1f,   { move.w  (a7)+,d7  ;get int value           }
      $205f,   { movea.l (a7)+,a0  ;get ptr to Int variable }
      $3087;   { move.w   d7, (a0) ;assign the Int value    }

   procedure Main;

implementation

{$S Main}

{--------------------------------------------------------------}
{  A routine to find the sum of the argument list              }
{    Called from BASIC as:                                     }
{    CALL IntSum (Sum, < Integer argument list >)              }
{--------------------------------------------------------------}
   procedure MAIN;
      var
          Sum, tempflag, argtype, NextInt: INT16;
          valptr, pSum: LIBARGPTR;

   begin
      Sum := 0;
      argtype := GetNextLibArg(pSum, tempflag);
      argtype := GetNextLibArg(valptr, tempflag);

      while (argtype <> _ARGSEND) do
         begin
            if (argtype <> _NULLARG) then
               begin
                 if (argtype = _STRGARG) then
                     BasicError(13)
                  else
                     begin
                        NextInt := IntegerArg;
                        Sum := Sum + NextInt;
                     end;
               end;
            argtype := GetNextLibArg(valptr, tempflag);
         end;

      AssignInt(pSum, Sum);
  end; {* of MAIN *}
				

Running SumInt produces the following output:

   Sum of:  2   4 and 8
   Is:  14