64bit_random.rb

module Id64 extend self
  Alphabet = "0123456789qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM_-"
  (Alphabet.size == 64) or raise "Alphabet should have 64 characters!"
  
  def random(length = 22)
    Array.new(length).map{ Alphabet[rand(2**6),1] }.join # 64**22 == 2**132
  end
end