    # File lib/nokogiri/css/tokenizer.rb, line 55
      def _next_token
        text = @ss.peek(1)
        @lineno  +=  1  if text == "\n"
        token = case @state
        when nil
          case
          when (text = @ss.scan(/has\([\s]*/))
             action { [:HAS, text] }

          when (text = @ss.scan(/[-@]?([_A-Za-z]|[^\0-\177]|\\[0-9A-Fa-f]{1,6}(\r\n|[\s])?|\\[^\n\r\f0-9A-Fa-f])([_A-Za-z0-9-]|[^\0-\177]|\\[0-9A-Fa-f]{1,6}(\r\n|[\s])?|\\[^\n\r\f0-9A-Fa-f])*\([\s]*/))
             action { [:FUNCTION, text] }

          when (text = @ss.scan(/[-@]?([_A-Za-z]|[^\0-\177]|\\[0-9A-Fa-f]{1,6}(\r\n|[\s])?|\\[^\n\r\f0-9A-Fa-f])([_A-Za-z0-9-]|[^\0-\177]|\\[0-9A-Fa-f]{1,6}(\r\n|[\s])?|\\[^\n\r\f0-9A-Fa-f])*/))
             action { [:IDENT, text] }

          when (text = @ss.scan(/\#([_A-Za-z0-9-]|[^\0-\177]|\\[0-9A-Fa-f]{1,6}(\r\n|[\s])?|\\[^\n\r\f0-9A-Fa-f])+/))
             action { [:HASH, text] }

          when (text = @ss.scan(/[\s]*~=[\s]*/))
             action { [:INCLUDES, text] }

          when (text = @ss.scan(/[\s]*\|=[\s]*/))
             action { [:DASHMATCH, text] }

          when (text = @ss.scan(/[\s]*\^=[\s]*/))
             action { [:PREFIXMATCH, text] }

          when (text = @ss.scan(/[\s]*\$=[\s]*/))
             action { [:SUFFIXMATCH, text] }

          when (text = @ss.scan(/[\s]*\*=[\s]*/))
             action { [:SUBSTRINGMATCH, text] }

          when (text = @ss.scan(/[\s]*!=[\s]*/))
             action { [:NOT_EQUAL, text] }

          when (text = @ss.scan(/[\s]*=[\s]*/))
             action { [:EQUAL, text] }

          when (text = @ss.scan(/[\s]*\)/))
             action { [:RPAREN, text] }

          when (text = @ss.scan(/[\s]*\[[\s]*/))
             action { [:LSQUARE, text] }

          when (text = @ss.scan(/[\s]*\]/))
             action { [:RSQUARE, text] }

          when (text = @ss.scan(/[\s]*\+[\s]*/))
             action { [:PLUS, text] }

          when (text = @ss.scan(/[\s]*>[\s]*/))
             action { [:GREATER, text] }

          when (text = @ss.scan(/[\s]*,[\s]*/))
             action { [:COMMA, text] }

          when (text = @ss.scan(/[\s]*~[\s]*/))
             action { [:TILDE, text] }

          when (text = @ss.scan(/\:not\([\s]*/))
             action { [:NOT, text] }

          when (text = @ss.scan(/-?([0-9]+|[0-9]*\.[0-9]+)/))
             action { [:NUMBER, text] }

          when (text = @ss.scan(/[\s]*\/\/[\s]*/))
             action { [:DOUBLESLASH, text] }

          when (text = @ss.scan(/[\s]*\/[\s]*/))
             action { [:SLASH, text] }

          when (text = @ss.scan(/U\+[0-9a-f?]{1,6}(-[0-9a-f]{1,6})?/))
             action {[:UNICODE_RANGE, text] }

          when (text = @ss.scan(/[\s]+/))
             action { [:S, text] }

          when (text = @ss.scan(/"([^\n\r\f"]|\n|\r\n|\r|\f|[^\0-\177]|\\[0-9A-Fa-f]{1,6}(\r\n|[\s])?|\\[^\n\r\f0-9A-Fa-f])*"|'([^\n\r\f']|\n|\r\n|\r|\f|[^\0-\177]|\\[0-9A-Fa-f]{1,6}(\r\n|[\s])?|\\[^\n\r\f0-9A-Fa-f])*'/))
             action { [:STRING, text] }

          when (text = @ss.scan(/./))
             action { [text, text] }

          else
            text = @ss.string[@ss.pos .. -1]
            raise  ScanError, "can not match: '" + text + "'"
          end  # if

        else
          raise  ScanError, "undefined state: '" + state.to_s + "'"
        end  # case state
        token
      end