Implement division without using * / %

I'll start by implementing multiplication to warm up

The first function relies on binary operation (shr and shl). It is way too complex but it is the first one I came up with. It looks ok but I haven't checked it. The second one is what I should have come up with at first.

def multiply (n,p)
        r = 0
        while p
                p2 = shr (p)
                if (p == 2*p + 1)
                        r += n
                n = shl(n)
                p = p2
        return r

def multiply2 (n,p)
        r = 0
        for k = 0 ; k < p k++
                r += n
        return r

Now for division, we understand that it will be almost as easy as multiply2.
General idea: we need to find q so that n = pq+r with r < p