Question

Ive got a problem. I send a pointer in function that replace 3 last elements of array to 3 first. I should use unsigned char array to send and it should work with ASM.

    int main(int argc, char* argv[])
{
    unsigned char arr[24]={
        1,2,3,4,5,6,
        7,8,9,10,11,12,
        13,14,15,16,17,18,
        19,20,21,22,23,24
        };// example

        AsmFlipVertical(arr);
};
void AsmFlipVertical(unsigned char  *arr)
{
_asm
    {
        les esi,arr ; esi=adress of first elem
        mov eax,esi
        add eax,21  
        mov edi,eax ; edi=adress of first elem+21;edi is a adress of 21th elem of array
        cld 
        mov ecx,3
        rep movsb 
    }
}

movsb from esi to edi
Ive got error in “rep movsb” What’s wrong? If use this ASM code in main function that’s okay,but I have to use ASM code in function…

Answer 1

You should not use any instructions that affect the segment registers in flat memory models. So, replace les esi,arr with mov esi,arr