Why Not a Function #14: uuids->named-uuid

(import '(java.nio ByteBuffer) '(java.util UUID))

(defn uuids->named-uuid
  [^UUID id1 ^UUID id2]
  (let [buffer (doto (ByteBuffer/allocate 32)
                 (.putLong (.getMostSignificantBits id1))
                 (.putLong (.getLeastSignificantBits id1))
                 (.putLong (.getMostSignificantBits id2))
                 (.putLong (.getLeastSignificantBits id2)))]
    (UUID/nameUUIDFromBytes (.array buffer))))

uuids->named-uuid “combines” two UUIDs into a version 3 namespace name-based UUID. This can be useful if we need a repeatable way of generating always the same UUID based on two known UUIDs.

(def id1 (UUID/randomUUID))
=> #'user/id1

(def id2 (UUID/randomUUID))
=> #'user/id2

id1
=> #uuid"9df3af32-dd8b-4d4b-9c3c-b3f6f674c3e7"

id2
=> #uuid"8af86769-a324-455d-a118-6703103c357d"

(uuids->named-uuid id1 id2)
=> #uuid"5a262f76-9504-3668-839e-c49319a11aea"

(uuids->named-uuid id1 id2)
=> #uuid"5a262f76-9504-3668-839e-c49319a11aea"

Written on March 30, 2020