Encode and Decode java.lang.Long as a web-safe, identically-sortable Base64 string. I.e., the Long and the string will both sort exactly the same way, and none of the characters of the string ever need to be escaped in a web context (e.g. in html, in xml, in any part of a url). Requires net.iharder.Base64 class which is Public Domain. See http:/…

b64longs.clj

(ns b64longs
  "Encode and Decode java.lang.Long as a web-safe, identically-sortable Base64 string.
  I.e., the Long and the string will both sort exactly the same way, and none of
  the characters of the string ever need to be escaped in a web context (e.g. in html,
  in xml, in any part of a url).

  Requires net.iharder.Base64 class which is Public Domain.
  See http://iharder.sourceforge.net/current/java/base64/

  Add this as a leinigen dependency.
  
      [net.iharder/base64 \"2.3.8\"]

  Example usage:
     (long->b64s 19234)
     ; => \"--------Hm7=\"
     (b64s->long \"--------Hm7=\")
     ; => 19234"
  (:import java.nio.ByteBuffer
           net.iharder.Base64))

(defn long->b64s
  "Return the string representation of a long in the ordered variant of Base64.
  The Base64 replacement table used is both web-safe and has the same lexical
  sorting as the bytes converted."
  [i]
  (Base64/encodeBytes
    (.. (ByteBuffer/allocate (/ Long/SIZE 8))
        (putLong i) (array))
    Base64/ORDERED))


(defn b64s->long
  "Return the long int represented by an ordered-Base64-encoded string."
  [s]
  (-> (.getBytes s "US-ASCII")
      (Base64/decode 0 12 Base64/ORDERED)
      (ByteBuffer/wrap)
      (.getLong)))