Convert UUIDs to/from base58

uu58.rb

module Uu58
  # Convert a string UUID to a base58 string representation.
  #
  # Output will be padded up to 22 digits if necessary.
  #
  # Behaviour is undefined if passing something other than a 128-bit
  # hex string in network order with optional interstitial hyphens.
  def self.uuid_to_base58(uuid, alphabet = SecureRandom::BASE58_ALPHABET)
    ary = uuid.delete("-").to_i(16).digits(58).reverse
    ary.unshift(0) while ary.length < 22
    alphabet.values_at(*ary).join
  end

  # Convert a base58 number to a UUID.
  #
  # Input should be a big-endian base58 string representation of
  # a whole number less than 2^128.
  def self.base58_to_uuid(base58_val, alphabet = SecureRandom::BASE58_ALPHABET)
    num = base58_val.chars.reverse_each.with_index.inject(0) do |acc, (digit, position)|
      digit_integer_value = alphabet.index(digit)
      raise ArgumentError, 'invalid base58 string' if digit_integer_value.nil?
      acc + digit_integer_value * 58**position
    end

    "%08x-%04x-%04x-%04x-%04x%08x" % [
      (num >> 96) & 0xFFFFFFFF,
      (num >> 80) & 0xFFFF,
      (num >> 64) & 0xFFFF,
      (num >> 48) & 0xFFFF,
      (num >> 32) & 0xFFFF,
      num & 0xFFFFFFFF
    ]
  end
end