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Created December 18, 2012 07:14
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Clojure - Calculate MD5 hash of a given string.
(import '
(defn md5 [s]
(let [algorithm (MessageDigest/getInstance "MD5")
size (* 2 (.getDigestLength algorithm))
raw (.digest algorithm (.getBytes s))
sig (.toString (BigInteger. 1 raw) 16)
padding (apply str (repeat (- size (count sig)) "0"))]
(str padding sig)))
; for full digest support, use clj-digest:
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To import MessageDigest try the import without the quote:


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For a version that works on anything extended with (like File):

(require '[ :as io])

(defn md5 [io-factory]
  (let [bytes'
        (with-open [xin (io/input-stream io-factory)
                    xout (ByteArrayOutputStream.)]
          (io/copy xin xout)
          (.toByteArray xout))
        algorithm (MessageDigest/getInstance "MD5")
        raw (.digest algorithm bytes')]
    (format "%032x" (BigInteger. 1 raw))))

(spit "test.txt" "foo\nbar\n")
(md5 (io/file "test.txt"))
; => "f47c75614087a8dd938ba4acff252494"

Still has the disadvantage of reading the whole file into a byte array at once though. If that's a concern for anyone I think there are some pretty simple solutions here:

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Is it possible to get back the raw bytes from the md5 String "%032x" format?

Simply doing "f47c75614087a8dd938ba4acff252494".getBytes() does not produce the same result as the digested raw byte[].

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