Map-reduce snippet for a blog post.

blog-map-reduce.clj

(ns blog-map-reduce.core
  (:import java.security.MessageDigest))

(defn digest [string]
  "Returns a SHA-1 digest of the given string."
  (.digest (MessageDigest/getInstance "SHA-1")
           (.getBytes string)))

(defn hex [bt]
  "Returns a hexadecimal value of the given byte."
  (if (< (bit-and 0xff bt) 0x10)
    (str 0 (Integer/toHexString (bit-and 0xff bt)))
    (Integer/toHexString (bit-and 0xff bt))))

(defn sha1 [string]
  "Returns a SHA-1 hash of the given string."
  (reduce str (map hex (digest string))))
  
(defn sha1-map [strings]
  "Returns a map of SHA-1 hashes as a keyword keys
   and given string as a value."
  (zipmap (map keyword (map sha1 strings)) strings))