/ memdif.s (emx+gcc) -- Copyright (c) 1993 by Eberhard Mattes

        .globl __memdif

/ size_t _memdif (const void *mem1, const void *mem2, size_t n)
/ {
/   size_t i;
/     
/   for (i = 0; i < n; ++i)
/     {
/       if (((char *)mem1)[i] != ((char *)mem2)[i])
/         return (i);
/     }
/   return (_MEMDIF_EQ);
/ }

/ assumes ds=es!

        .text

        .align  2, 0x90

__memdif:
        pushl   %esi
        pushl   %edi
        movl    3*4(%esp), %edi         / mem1
        movl    4*4(%esp), %esi         / mem2
        movl    5*4(%esp), %ecx         / n
        xorl    %eax, %eax
        jecxz   1f
        repe
        cmpsb
        je      1f
        decl    %edi
        subl    3*4(%esp), %edi
        movl    %edi, %eax
        jmp     9f

1:      movl    $-1, %eax               / _MEMDIF_EQ
9:      popl    %edi
        popl    %esi
        ret