SecureRandom#base64_urlsafe_uuid

securerandom.rb

module Random::Formatter
  # SecureRandom.base64_urlsafe_uuid generates a random v4 UUID (Universally Unique IDentifier) base64 string.
  #
  #   p SecureRandom.base64_urlsafe_uuid #=> "bg4vleJWQvuhyikuUJy3MA"
  #   p SecureRandom.base64_urlsafe_uuid #=> "KQn-06XIT3ShqWaZz4kXuA"
  #   p SecureRandom.base64_urlsafe_uuid #=> "jlu3dBFcQb-8MTAfoOZXRg"
  #
  # The version 4 UUID is purely random (except the version).
  # It doesn't contain meaningful information such as MAC addresses, timestamps, etc.
  #
  # The result contains 122 random bits (15.25 random bytes).
  #
  # See RFC 4122 for details of UUID.
  #
  # The uuid format produces 36 bytes and the base64 encoded format produces 22 bytes.
  # This format has the advantage of saving 14 bytes per uuid.
  def base64_urlsafe_uuid
    ary = random_bytes(16).unpack("NnnnnN")
    ary[2] = (ary[2] & 0x0fff) | 0x4000
    ary[3] = (ary[3] & 0x3fff) | 0x8000
    bin = ["%08x%04x%04x%04x%04x%08x" % ary].pack('H*')
    [bin].pack("m0").tr("+/", "-_").delete("=")
  end
end