hash_of.clj

(defmulti hash-of
  "Returns a string representation of a SHA1 hash of the provided data, which can be
   a File, byte[], String (which will be converted to UTF-8 byte[]), or an InputStream."
  class)

(defmethod hash-of String
  [#^String s]
  (hash-of (.getBytes s "UTF-8")))

(defmethod hash-of (class (make-array Byte/TYPE 0))
  [bytes]
  (hash-of (java.io.ByteArrayInputStream. bytes)))

(defmethod hash-of java.io.File
  [#^java.io.File f]
  (-> f java.io.FileInputStream. java.io.BufferedInputStream. hash-of))

(defmethod hash-of java.io.InputStream
  [#^java.io.InputStream is]
  (let [digest (MiscUtilities/createDigester "SHA1")
        arr (make-array Byte/TYPE 2048)]
    (loop [len (.read is arr)]
      (when-not (== -1 len)
        (.update digest arr 0 len)
        (recur (.read is arr))))
    (-> digest .digest MiscUtilities/toHex)))