API: Storage StorageEngineSWF.js (YUI Library)

# Yahoo! UI Library

### Storage 2.8.1

Yahoo! UI Library > Storage > StorageEngineSWF.js (source view)
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    /*
     * SWF limitation:
     *  - only 100,000 bytes of data may be stored this way
     *  - data is publicly available on user machine
     *
     * Thoughts:
     *  - data can be shared across browsers
     *  - how can we not use cookies to handle session location
     */
    (function() {
        // internal shorthand
    var Y = YAHOO.util,
        YL = YAHOO.lang,
        YD = Y.Dom,

        /*
         * The minimum width required to be able to display the settings panel within the SWF.
         */
        MINIMUM_WIDTH = 215,

        /*
         * The minimum height required to be able to display the settings panel within the SWF.
         */
        MINIMUM_HEIGHT = 138,

        // local variables
        _engine = null,

        /*
         * Creates a location bound key.
         */
        _getKey = function(that, key) {
            return that._location + that.DELIMITER + key;
        },

        /*
         * Initializes the engine, if it isn't already initialized.
         */
        _initEngine = function(cfg) {
            if (! _engine) {
                if (! YL.isString(cfg.swfURL)) {cfg.swfURL = Y.StorageEngineSWF.SWFURL;}
                if (! cfg.containerID) {
                    var bd = document.getElementsByTagName('body')[0],
                        container = bd.appendChild(document.createElement('div'));
                    cfg.containerID = YD.generateId(container);
                }

                if (! cfg.attributes) {cfg.attributes  = {};}
                if (! cfg.attributes.flashVars) {cfg.attributes.flashVars = {};}
                cfg.attributes.flashVars.useCompression = 'true';
                cfg.attributes.version = 9.115;
                _engine = new YAHOO.widget.SWF(cfg.containerID, cfg.swfURL, cfg.attributes);
            }
        };

        /**
         * The StorageEngineSWF class implements the SWF storage engine.
         * @namespace YAHOO.util
         * @class StorageEngineSWF
         * @uses YAHOO.widget.SWF
         * @constructor
         * @extend YAHOO.util.Storage
         * @param location {String} Required. The storage location.
         * @param conf {Object} Required. A configuration object.
         */
        Y.StorageEngineSWF = function(location, conf) {
            var _this = this;
            Y.StorageEngineSWF.superclass.constructor.call(_this, location, Y.StorageEngineSWF.ENGINE_NAME, conf);

            _initEngine(_this._cfg);

            // evaluates when the SWF is loaded
    		_engine.unsubscribe('contentReady'); // prevents local and session content ready callbacks from firing, when switching between context
            _engine.addListener("contentReady", function() {
                _this._swf = _engine._swf;
                _engine.initialized = true;

    			var isSessionStorage = Y.StorageManager.LOCATION_SESSION === _this._location,
    				sessionKey = Y.Cookie.get('sessionKey' + Y.StorageEngineSWF.ENGINE_NAME);

                for (var i = _engine.callSWF("getLength", []) - 1; 0 <= i; i -= 1) {
                    var key = _engine.callSWF("getNameAt", [i]),
                        isKeySessionStorage = -1 < key.indexOf(Y.StorageManager.LOCATION_SESSION + _this.DELIMITER);

                    // this is session storage, but the session key is not set, so remove item
                    if (isSessionStorage && ! sessionKey) {
                        _engine.callSWF("removeItem", [key]);
                    }
                    // the key matches the storage type, add to key collection
                    else if (isSessionStorage === isKeySessionStorage) {
                        _this._addKey(key);
                    }
                }

                // this is session storage, ensure that the session key is set
                if (isSessionStorage) {
                    Y.Cookie.set('sessionKey' + Y.StorageEngineSWF.ENGINE_NAME, true);
                }

                _this.length = _this._keys.length;
                _this.fireEvent(_this.CE_READY);
            });

            // required for pages with both a session and local storage
            if (_engine.initialized) {_engine.fireEvent('contentReady');}
        };

        YL.extend(Y.StorageEngineSWF, Y.StorageEngineKeyed, {
            /**
             * The underlying SWF of the engine, exposed so developers can modify the adapter behavior.
             * @property _swf
             * @type {Object}
             * @protected
             */
            _swf: null,

            /*
             * Implementation to clear the values from the storage engine.
             * @see YAHOO.util.Storage._clear
             */
            _clear: function() {
                for (var i = this._keys.length - 1; 0 <= i; i -= 1) {
                    var key = this._keys[i];
                    _engine.callSWF("removeItem", [key]);
                }

                this._keys = [];
                this.length = 0;
            },

            /*
             * Implementation to fetch an item from the storage engine.
             * @see YAHOO.util.Storage._getItem
             */
            _getItem: function(key) {
                var _key = _getKey(this, key);
                return _engine.callSWF("getValueOf", [_key]);
            },

            /*
             * Implementation to fetch a key from the storage engine.
             * @see YAHOO.util.Storage.key
             */
            _key: function(index) {
                return (this._keys[index] || '').replace(/^.*?__/, '');
            },

            /*
             * Implementation to remove an item from the storage engine.
             * @see YAHOO.util.Storage._removeItem
             */
            _removeItem: function(key) {
                var _key = _getKey(this, key);
                _engine.callSWF("removeItem", [_key]);
                this._removeKey(_key);
            },

            /*
             * Implementation to remove an item from the storage engine.
             * @see YAHOO.util.Storage._setItem
             */
            _setItem: function(key, data) {
                var _key = _getKey(this, key), swfNode;

                // setting the value returns false if the value didn't change,
                // so I changed this to clear the key if it exists so that the
                // fork below works.
                if (_engine.callSWF("getValueOf", [_key])) {
                    this._removeItem(key);
                }

                this._addKey(_key);

                if (_engine.callSWF("setItem", [_key, data])) {
                    return true;
                } else {

                    // @TODO we should not assume that a false return means that
                    // the quota has been exceeded.  this dialog should only be
                    // displayed if the quotaExceededError event fired.
                    swfNode = YD.get(_engine._id);
                    if (MINIMUM_WIDTH > YD.getStyle(swfNode, 'width').replace(/\D+/g, '')) {
                        YD.setStyle(swfNode, 'width', MINIMUM_WIDTH + 'px');
                    }
                    if (MINIMUM_HEIGHT > YD.getStyle(swfNode, 'height').replace(/\D+/g, '')) {
                        YD.setStyle(swfNode, 'height', MINIMUM_HEIGHT + 'px');
                    }
                    return _engine.callSWF("displaySettings", []);
                }
            }
        });

        Y.StorageEngineSWF.SWFURL = "swfstore.swf";
        Y.StorageEngineSWF.ENGINE_NAME = 'swf';
        Y.StorageEngineSWF.isAvailable = function() {
            return (6 <= YAHOO.env.ua.flash && YAHOO.widget.SWF);
        };
        Y.StorageManager.register(Y.StorageEngineSWF);
    }());

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