Random UUID compressed into a Binary 16 byte array in Clojure.

binary16-uuid.clj

;; Random UUID compressed into a Binary 16 byte array in Clojure.
;; by James Thornton, http://jamesthornton.com

(ns espeed.uuid
  (require  [clojure.data.codec.base64 :as b64]))


(defn uuid4 [] (java.util.UUID/randomUUID))

(defn uuid-as-byte-array []
  (let [u (uuid4)                              ; uuid4
        ^long lo (.getLeastSignificantBits u)  ; least significant bits
        ^long hi (.getMostSignificantBits u)]  ; most significant bits (left-most bits)
    (-> (java.nio.ByteBuffer/allocate 16)      ; http://docs.oracle.com/javase/6/docs/api/java/util/UUID.html
      (.putLong hi)
      (.putLong lo)
      (.array))))

(defn bytes-to-base64-bytes
  [bytes]
  (b64/encode bytes))

(defn bytes-to-base64-str
  [bytes]
  (-> bytes b64/encode (String. "UTF-8")))

;; originally derived from...
;; http://corfield.org/blog/post.cfm/to-uuid-or-not-to-uuid

(comment defn uuid2 [] (com.eaio.uuid.UUID.))
(comment defn uuid-as-byte-array []
  (let [u (uuid2)                         
        ^long lo (.getClockSeqAndNode u)  
        ^long hi (.getTime u)]            
    (-> (java.nio.ByteBuffer/allocate 16) 
      (.putLong hi)
      (.putLong lo)
      (.array))))


;; Notes...
;; http://www.thebinaryidiot.com/archives/2011/06/25/jpa-and-uuid-primary-keys/
;; http://www.mysqlperformanceblog.com/2007/03/13/to-uuid-or-not-to-uuid/
;; https://bugzilla.mozilla.org/show_bug.cgi?id=843013
;; https://news.ycombinator.com/item?id=2339120
;; http://stackoverflow.com/questions/11825444/clojure-base64-encoding