Universally Unique Lexicographically Sortable Identifier for Lua

Based on the implementation by alizain

UUID can be suboptimal for many uses-cases because:

It isn't the most character efficient way of encoding 128 bits of randomness
UUID v1/v2 is impractical in many environments, as it requires access to a unique, stable MAC address
UUID v3/v5 requires a unique seed and produces randomly distributed IDs, which can cause fragmentation in many data structures
UUID v4 provides no other information than randomness which can cause fragmentation in many data structures

Instead, herein is proposed ULID:

128-bit compatibility 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)

Lua

Installation

luarocks install ulid

Usage

local ulid_mod = require("ulid")

print(ulid_mod.ulid())  -- 01ARZ3NDEKTSV4RRFFQ69G5FAV

Specification

Below is the current specification of ULID as implemented in this repository.

Note: the binary format has not been implemented.

 01AN4Z07BY      79KA1307SR9X4MV3

|----------|    |----------------|
 Timestamp          Randomness
   48bits             80bits

Components

Timestamp

48 bit integer
UNIX-time in milliseconds
Won't run out of space till the year 10895 AD.

Randomness

80 bits
Please make sure to use cryptographically secure source of randomness, if possible

Sorting

The left-most character must be sorted first, and the right-most character sorted last (lexical order). The default ASCII character set must be used. Within the same millisecond, sort order is not guaranteed

Encoding

Crockford's Base32 is used as shown. This alphabet excludes the letters I, L, O, and U to avoid confusion and abuse.

0123456789ABCDEFGHJKMNPQRSTVWXYZ

String Representation

ttttttttttrrrrrrrrrrrrrrrr

where
t is Timestamp
r is Randomness

Test Suite

Tests can be run from the repo using busted

busted

License

Tieske/ulid.lua

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