to_case

# File activesupport/lib/active_support/multibyte/handlers/utf8_handler.rb, line 453
      def to_case(way, str)
        u_unpack(str).map do |codepoint|
          cp = UCD[codepoint] 
          unless cp.nil?
            ncp = cp.send(way)
            ncp > 0 ? ncp : codepoint
          else
            codepoint
          end
        end.pack('U*')
      end