Turning a binary matrix into a vector of the last nonzero index in a fast, vectorized fashion

Suppose, in MATLAB, that I have a matrix, A, whose elements are either 0 or 1.

How do I get a vector of the index of the last non-zero element of each column in a faster, vectorized way?

I could do

[B, I] = max(cumsum(A));

and use I, but is there a faster way? (I'm assuming cumsum would cost a bit of time even suming 0's and 1's).

Edit: I guess that I vectorized even more than I need fast - Mr. Fooz' loop is great but each loop in MATLAB seems to cost me a lot in debugging time even if it is fast.