# 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