# File lib/openid/store/filesystem.rb, line 29
      def get_association_filename(server_url, handle)
        unless server_url.index('://')
          raise ArgumentError, "Bad server URL: #{server_url}"
        end

        proto, rest = server_url.split('://', 2)
        domain = filename_escape(rest.split('/',2)[0])
        url_hash = safe64(server_url)
        if handle
          handle_hash = safe64(handle)
        else
          handle_hash = ''
        end
        filename = [proto,domain,url_hash,handle_hash].join('-')
        @association_dir.join(filename)
      end