The source code

    /**
     * @ignore
     *  use flash to accomplish cross domain request, usage scenario ? why not jsonp ?
     * @author yiminghe@gmail.com
     */
    KISSY.add('ajax/xdr-flash-transport', function (S, io, DOM) {

        var // current running request instances
            maps = {},
            ID = 'io_swf',
        // flash transporter
            flash,
            doc = S.Env.host.document,
        // whether create the flash transporter
            init = false;

        // create the flash transporter
        function _swf(uri, _, uid) {
            if (init) {
                return;
            }
            init = true;
            var o = '<object id="' + ID +
                    '" type="application/x-shockwave-flash" data="' +
                    uri + '" width="0" height="0">' +
                    '<param name="movie" value="' +
                    uri + '" />' +
                    '<param name="FlashVars" value="yid=' +
                    _ + '&uid=' +
                    uid +
                    '&host=KISSY.require(\'ajax\')" />' +
                    '<param name="allowScriptAccess" value="always" />' +
                    '</object>',
                c = doc.createElement('div');
            DOM.prepend(c, doc.body || doc.documentElement);
            c.innerHTML = o;
        }

        function XdrFlashTransport(io) {
            S.log('use XdrFlashTransport for: ' + io.config.url);
            this.io = io;
        }

        S.augment(XdrFlashTransport, {
            // rewrite send to support flash xdr
            send: function () {
                var self = this,
                    io = self.io,
                    c = io.config,
                    xdr = c['xdr'] || {};
                // 不提供则使用 cdn 默认的 flash
                _swf(xdr.src || (S.Config.base + 'ajax/io.swf'), 1, 1);
                // 简便起见，用轮训
                if (!flash) {
                    // S.log('detect xdr flash');
                    setTimeout(function () {
                        self.send();
                    }, 200);
                    return;
                }
                self._uid = S.guid();
                maps[self._uid] = self;

                // ie67 send 出错？
                flash.send(io._getUrlForSend(), {
                    id: self._uid,
                    uid: self._uid,
                    method: c.type,
                    data: c.hasContent && c.data || {}
                });
            },

            abort: function () {
                flash.abort(this._uid);
            },

            _xdrResponse: function (e, o) {
                // S.log(e);
                var self = this,
                    ret,
                    id = o.id,
                    responseText,
                    c = o.c,
                    io = self.io;

                // need decodeURI to get real value from flash returned value
                if (c && (responseText = c.responseText)) {
                    io.responseText = decodeURI(responseText);
                }

                switch (e) {
                    case 'success':
                        ret = { status: 200, statusText: 'success' };
                        delete maps[id];
                        break;
                    case 'abort':
                        delete maps[id];
                        break;
                    case 'timeout':
                    case 'transport error':
                    case 'failure':
                        delete maps[id];
                        ret = {
                            status: 'status' in c ? c.status : 500,
                            statusText: c.statusText || e
                        };
                        break;
                }
                if (ret) {
                    io._ioReady(ret.status, ret.statusText);
                }
            }
        });

        /*called by flash*/
        io['applyTo'] = function (_, cmd, args) {
            // S.log(cmd + ' execute');
            var cmds = cmd.split('.').slice(1),
                func = io;
            S.each(cmds, function (c) {
                func = func[c];
            });
            func.apply(null, args);
        };

        // when flash is loaded
        io['xdrReady'] = function () {
            flash = doc.getElementById(ID);
        };

        /*
         when response is returned from server
         @param e response status
         @param o internal data
         */
        io['xdrResponse'] = function (e, o) {
            var xhr = maps[o.uid];
            xhr && xhr._xdrResponse(e, o);
        };

        return XdrFlashTransport;

    }, {
        requires: ['./base', 'dom']
    });