wouldnt a interupt based debouncer more efficient
i can provide code in ANSI C, that works quite well
well you still have to have an array of unsigned bytes to store results and some bit array to stock kbd debounced state(with a student abused, cola filled matrix 4*4 kbd i had fair results, and i must admit much better than any loop could be) since low grade kbd button has something like 40 ms oscillation time (if you use better HW cold be LOT BETTER)