ULID implementation in Common Lisp

A ULID is a universally unique lexicographically sortable identifier.

It is:

128-bit compatible with UUID
1.21e+24 unique ULIDs per millisecond
Lexicographically sortable!
Canonically encoded as a 26 character string, as opposed to the 36 character UUID
Uses Crockford’s base32 for better efficiency and readability (5 bits per character)
Case insensitive
No special characters (URL safe)

In general the structure of a ULID is as follows:

01AN4Z07BY	79KA1307SR9X4MV3
Timestamp	Randomness
48bits	80bits

For more information have a look at the original specification.

Installation

cl-ulid is not in quicklisp. It will need to be installed in the local-projects quicklisp directory:

> cd /$USER_HOME/quicklisp/local-projects/
> git clone https://github.com/jolby/cl-ulid.git

Basic Usage at the REPL

CL-USER>(ql:quickload :cl-ulid)
> (:CL-ULID)
CL-USER> ;; (ulid:ulid) returns the values of a ULID encoded as a string as well as a byte array
CL-USER> (ulid::ulid)
>"01H7NR28J0FEDWV9G66ZRKJY4V"
#(1 137 235 129 34 64 123 155 205 166 6 55 241 57 120 155)
CL-USER> ;; (Retrieve the encoded values from the string or byte array
CL-USER> (let* ((ulid-generator (ulid:make-ulid-generator :random-number-fn (lambda (x) 1)))
                (time (ulid:get-unix-time-ms)))
           (multiple-value-bind (ulid-str ulid-bytes) (funcall ulid-generator time)
             (multiple-value-bind (ts random) (ulid:decode-to-values ulid-str)
               (assert (= ts time))
               (assert (= random 1)))
             (multiple-value-bind (ts random) (ulid:decode-to-values ulid-bytes)
               (assert (= ts time))
               (assert (= random 1))))
           (format nil "DONE~%"))

Strong Random

The default cl-ulid system uses ironclad’s strong-random for the RNG. It is very easy to provide another RNG source if desired. Look at the ironclad-random.lisp file to see how it is done.

Other Common Lisp implementations.

There is at least one other common lisp implementation that I know of: https://gitlab.com/colinstrickland/cms-ulid.git

Unfortunately, I was already in the middle of this implementation when I found that one. The code in that implementation seems cleaner than this project, but it probably never hurts to have more than one implementation to choose from.