(defn stack-hash
    "Creates a hash of in which fits in size with minimal rehashing given various sizes. Optional n argument can be specified if it has been precomputed"
    [in size]
    (let [n (Math/ceil (/ (Math/log size) (Math/log 2)))
          mask (int (- (Math/pow 2 n) 1))]
        (loop [in in]
            (let [Hv (loop [i 0
                            h 0]
                        (if (> (count in) i)
                            (recur  (+ i 1)
                                (mod (+ (* h 31) (int (.charAt in i))) Integer/MAX_VALUE))
                        h))
                  first-four (bit-and Hv mask)]
                (if (< first-four size)
                    first-four
                    (recur (str first-four)))))
    ))