which_encoding (OpenID::Server::ProtocolError)

    # File lib/openid/server.rb, line 1458
          def which_encoding
            if has_return_to()
              if @openid_message.is_openid2 and
                  encode_to_url().length > OPENID1_URL_LIMIT
                return ENCODE_HTML_FORM
              else
                return ENCODE_URL
              end
            end

            if @openid_message.nil?
              return nil
            end

            mode = @openid_message.get_arg(OPENID_NS, 'mode')
            if mode
              if !BROWSER_REQUEST_MODES.member?(mode)
                return ENCODE_KVFORM
              end
            end

            # If your request was so broken that you didn't manage to
            # include an openid.mode, I'm not going to worry too much
            # about returning you something you can't parse.
            return nil
          end