class Redis::SubscribedClient

def subscription(start, stop, channels, block)
  sub = Subscription.new(&block)
  unsubscribed = false
  begin
    @client.call_loop([start, *channels]) do |line|
      type, *rest = line
      sub.callbacks[type].call(*rest)
      unsubscribed = type == stop && rest.last == 0
      break if unsubscribed
    end
  ensure
    # No need to unsubscribe here. The real client closes the connection
    # whenever an exception is raised (see #ensure_connected).
  end
end