hashing.clj

(ns clj-hashing
  (:import
    [com.google.common.hash     Hashing HashFunction HashCode ]
    [java.nio.charset           Charset                       ]))

  (def ^:private ^HashFunction murmur-fun (Hashing/murmur3_128))
  (def ^:private ^HashFunction sha1-fun   (Hashing/sha1))
  (def ^:private ^HashFunction md5-fun    (Hashing/md5))

  (def ^:private ^sun.nio.cs.UTF_8 utf8-chr-set (Charset/forName "UTF-8"))

  (defn gen-hash-no-type 
    "General generator for hashing functions"
    [fun] 
    (fn [string] 
      (.toString (.hashString fun string utf8-chr-set))))

  (def murmur2 (gen-hash-no-type murmur-fun))

  (defn gen-hash 
    "General generator for hashing functions"
    [^HashFunction fun] 
    (fn ^String [^String string] 
      (.toString (.hashString fun string utf8-chr-set))))

  (def murmur (gen-hash murmur-fun))
  (def sha1   (gen-hash sha1-fun))
  (def md5    (gen-hash md5-fun))

;clj-hashing=> (time (count (map murmur (repeat 10000 "asdf"))))
;"Elapsed time: 8.523 msecs"
;10000
;clj-hashing=> (time (count (map murmur2 (repeat 10000 "asdf"))))
;"Elapsed time: 48.583 msecs"
;10000