DOCUMENT:Q61590  06-MAY-2001  [masm]
TITLE   :Passing a long* from a C Module to an Assembly Module
PRODUCT :Microsoft Macro Assembler
PROD/VER::5.1,5.1a,6.0,6.0a,6.0b
OPER/SYS:
KEYWORDS:

======================================================================
-------------------------------------------------------------------------------
The information in this article applies to:

 - Microsoft Macro Assembler (MASM), versions 5.1, 5.1a, 6.0, 6.0a, 6.0b 
-------------------------------------------------------------------------------

SUMMARY
=======

The following code demonstrates passing a LONG INT (4 bytes) via a far pointer
(4 bytes) to an assembly routine that accesses the LONG integer.

Each integer is incremented in the assembly routine and its new value returned to
the calling C program.

MORE INFORMATION
================

Sample Code
-----------

   /* Compile options needed: /AL
   */ 

   #include <stdio.h>
   #include <process.h>
   #include <conio.h>

   extern void IncLongs( long *, long * );

   void main()
   {
      long *n1,*n2;               /* 4 byte pointers  */ 

      long int t1 = 9999999L;     /* 4 byte variables */ 
      long int t2 = 2256789L;

      n1 = &t1;
      n2 = &t2;

      /* initial values */ 
      printf( "The values are  %ld and  %ld\n ", *n1, *n2 );

      printf( "Incrementing values...\n" );
      IncLongs( n1, n2 );

      /* values returned by the assembly routine */ 
      printf( "The values are  %ld and  %ld\n ", *n1, *n2 );
   }

   ========================================================

   ; Assemble options needed: none

            .model large, c
            .data
            .code
   IncLongs PROC far arg1:dword, arg2:dword
            PUSH es                 ; save registers
            PUSH si
            LES si,arg1             ; load in es:si the seg:offset of n1
            INC word ptr es:[si]
            JNC doarg2
            INC word ptr es:[si+2]  ; if carry, increment high word of n1

   doarg2:
            LES si,arg2             ; load in es:si the seg:offset of n2
            INC word ptr es:[si]
            JNC finis
            INC word ptr es:[si+2]  ; if carry, increment high word of n2

   finis:
            POP si                  ; restore registers
            POP es
            MOV sp,bp
            RET
   IncLongs ENDP

            END

Additional query words: 5.10 5.10a 6.00 6.00a 6.00b

======================================================================
Keywords          :  
Technology        : kbMASMsearch kbAudDeveloper kbMASM510 kbMASM600 kbMASM600a kbMASM510a kbMASM600b
Version           : :5.1,5.1a,6.0,6.0a,6.0b

=============================================================================

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