Q61590

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page	Q61590: Passing a LONG INT in C to an Assembly Module	/pubs/pc/reference/microsoft/kb/Q61590/

Q61590: Passing a LONG INT in C to an Assembly Module

Article: Q61590
Version(s): 5.10 5.10a
Operating System: MS-DOS
Flags: ENDUSER |
Last Modified: 21-MAY-1990

The following code demonstrates passing a LONG INT (4 bytes) via a
LONG 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.

The code is as follows:

*********************************************************

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

 extern void stuff (long *, long *);

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");
  stuff(n1,n2);

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

}

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

.LALL
.model large,C
.data
.code
  stuff 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 then increment the 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 then increment the high
                           ;word of n2
finis:
    pop si                 ;restore registers
    pop es
    mov sp,bp
    ret
  stuff endp

  end

*********************************************************
*Makefile 'new':-
*
*all=1.obj 2.obj    (macro for all the obj's)
*
*1.obj: 1.c         (compiles the C module)
*  cl /AL /c 1.c
*
*2.obj: 2.asm       (assembles the Assembler module)
*  masm 2.asm,,2;
*
*1.exe: $(all)      (links modules with library)
*   link /co $(all),,1,/nod llibcer;  (emulator lib name)
*
*Command Line to run makefile:  MAKE new
*
*********************************************************