Passing array as a parameter to an external ASM (Assembly) x86 and accessing it

Question

As there isn't too much information I could find on mixing C++ and Assembly, I wanted some clarification on some issues I am having with assembly.

I am working on a project where we have to pass an array to a separate .asm document in order to reverse the string. Please see the code of the .cpp file I started with (not including header below):

extern"C" int swap(char*, int);

int main()
{
    const int SIZE = 20;
    char str1[20] = { '\0' };

    cout << "Please enter a string: ";
    cin >> str1;

    swap(str1,SIZE);

    return 0;
}

From here, I would start the following in my .asm document (not including the header in the code below):

_swap PROC
    push ebp
    mov ebp,esp ;stack pointer to ebp

    mov ebx,[ebp+8] ; address of first array element
    mov ecx,[ebp+12]

The asm code above is what was shown in class to access the array. At this point, does the pointer iterate to the next index if I add 4 to ebx register?

Let say the first index (0) in my array is 'a'. Does performing mov ebx,[ebp+8] set ebx to the address of where 'a' is? If so, incrementing ebx 4 bytes should move it to the next index, correct?

Since I am still learning and this is very new to me, I apologize for any syntax mistakes. I believe I am just trying to get more clarifications rather than answers.

Answer 1

At this point, does the pointer iterate to the next index if I add 4 to ebx register?

Your declaration of swap is extern"C" int swap(char*, int);

Since the pointer is a pointer to char , you should add 1 to ebx to make it point to the next element.