Nano squids

nanosquid.clj

;; for comparison, have the squid generator from the clojure cookbook that uses seconds
;; from https://github.com/clojure-cookbook/clojure-cookbook/blob/master/01_primitive-data/1-24_uuids.asciidoc
(defn squuid-secs []
  (let [uuid (java.util.UUID/randomUUID)
        time (System/currentTimeMillis)
        secs (quot time 1000)
        lsb (.getLeastSignificantBits uuid)
        msb (.getMostSignificantBits uuid)
        timed-msb (bit-or (bit-shift-left secs 32)
                          (bit-and 0x00000000ffffffff msb))]
    (java.util.UUID. timed-msb lsb)))

;; let's see if it's okay
(let [squids (take 10 (repeatedly squuid-secs))]
  (assert (= squids (sort squids))))

;; how about using nanoseconds instead?
(defn squuid-nanos []
  (let [uuid (java.util.UUID/randomUUID)
        time (System/nanoTime)
        lsb (.getLeastSignificantBits uuid)
        msb (.getMostSignificantBits uuid)
        timed-msb (bit-or (bit-shift-left time 32)
                          (bit-and 0x00000000ffffffff msb))]
    (java.util.UUID. timed-msb lsb)))

;; let's see if it's okay
(let [squids (take 10 (repeatedly squuid-nanos))]
  (assert (= squids (sort squids))))