# File lib/gibbler.rb, line 558
    def __gibbler(digest_type=nil)
      klass = self.class
      if self.nil? 
        first, last, exclude = "\0", "\0", "\0"
      else
        first, last, exclude = self.first, self.last, self.exclude_end?
      end
      a = Gibbler.digest "%s:%s:%s:%s" % [klass, exclude, first, last], digest_type
      gibbler_debug klass, a, [klass, exclude, first, last]
      a
    end