resources/lib/jquery/jquery.jStorage.js

   1 /*
   2  * ----------------------------- JSTORAGE -------------------------------------
   3  * Simple local storage wrapper to save data on the browser side, supporting
   4  * all major browsers - IE6+, Firefox2+, Safari4+, Chrome4+ and Opera 10.5+
   5  *
   6  * Author: Andris Reinman, andris.reinman@gmail.com
   7  * Project homepage: www.jstorage.info
   8  *
   9  * Licensed under Unlicense:
  10  *
  11  * This is free and unencumbered software released into the public domain.
  12  *
  13  * Anyone is free to copy, modify, publish, use, compile, sell, or
  14  * distribute this software, either in source code form or as a compiled
  15  * binary, for any purpose, commercial or non-commercial, and by any
  16  * means.
  17  *
  18  * In jurisdictions that recognize copyright laws, the author or authors
  19  * of this software dedicate any and all copyright interest in the
  20  * software to the public domain. We make this dedication for the benefit
  21  * of the public at large and to the detriment of our heirs and
  22  * successors. We intend this dedication to be an overt act of
  23  * relinquishment in perpetuity of all present and future rights to this
  24  * software under copyright law.
  25  *
  26  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  27  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  28  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
  29  * IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  30  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  31  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  32  * OTHER DEALINGS IN THE SOFTWARE.
  33  *
  34  * For more information, please refer to <http://unlicense.org/>
  35  */
  36
  37  (function(){
  38     var
  39         /* jStorage version */
  40         JSTORAGE_VERSION = "0.4.8",
  41
  42         /* detect a dollar object or create one if not found */
  43         $ = window.jQuery || window.$ || (window.$ = {}),
  44
  45         /* check for a JSON handling support */
  46         JSON = {
  47             parse:
  48                 window.JSON && (window.JSON.parse || window.JSON.decode) ||
  49                 String.prototype.evalJSON && function(str){return String(str).evalJSON();} ||
  50                 $.parseJSON ||
  51                 $.evalJSON,
  52             stringify:
  53                 Object.toJSON ||
  54                 window.JSON && (window.JSON.stringify || window.JSON.encode) ||
  55                 $.toJSON
  56         };
  57
  58     // Break if no JSON support was found
  59     if(!("parse" in JSON) || !("stringify" in JSON)){
  60         throw new Error("No JSON support found, include //cdnjs.cloudflare.com/ajax/libs/json2/20110223/json2.js to page");
  61     }
  62
  63     var
  64         /* This is the object, that holds the cached values */
  65         _storage = {__jstorage_meta:{CRC32:{}}},
  66
  67         /* Actual browser storage (localStorage or globalStorage["domain"]) */
  68         _storage_service = {jStorage:"{}"},
  69
  70         /* DOM element for older IE versions, holds userData behavior */
  71         _storage_elm = null,
  72
  73         /* How much space does the storage take */
  74         _storage_size = 0,
  75
  76         /* which backend is currently used */
  77         _backend = false,
  78
  79         /* onchange observers */
  80         _observers = {},
  81
  82         /* timeout to wait after onchange event */
  83         _observer_timeout = false,
  84
  85         /* last update time */
  86         _observer_update = 0,
  87
  88         /* pubsub observers */
  89         _pubsub_observers = {},
  90
  91         /* skip published items older than current timestamp */
  92         _pubsub_last = +new Date(),
  93
  94         /* Next check for TTL */
  95         _ttl_timeout,
  96
  97         /**
  98          * XML encoding and decoding as XML nodes can't be JSON'ized
  99          * XML nodes are encoded and decoded if the node is the value to be saved
 100          * but not if it's as a property of another object
 101          * Eg. -
 102          *   $.jStorage.set("key", xmlNode);        // IS OK
 103          *   $.jStorage.set("key", {xml: xmlNode}); // NOT OK
 104          */
 105         _XMLService = {
 106
 107             /**
 108              * Validates a XML node to be XML
 109              * based on jQuery.isXML function
 110              */
 111             isXML: function(elm){
 112                 var documentElement = (elm ? elm.ownerDocument || elm : 0).documentElement;
 113                 return documentElement ? documentElement.nodeName !== "HTML" : false;
 114             },
 115
 116             /**
 117              * Encodes a XML node to string
 118              * based on http://www.mercurytide.co.uk/news/article/issues-when-working-ajax/
 119              */
 120             encode: function(xmlNode) {
 121                 if(!this.isXML(xmlNode)){
 122                     return false;
 123                 }
 124                 try{ // Mozilla, Webkit, Opera
 125                     return new XMLSerializer().serializeToString(xmlNode);
 126                 }catch(E1) {
 127                     try {  // IE
 128                         return xmlNode.xml;
 129                     }catch(E2){}
 130                 }
 131                 return false;
 132             },
 133
 134             /**
 135              * Decodes a XML node from string
 136              * loosely based on http://outwestmedia.com/jquery-plugins/xmldom/
 137              */
 138             decode: function(xmlString){
 139                 var dom_parser = ("DOMParser" in window && (new DOMParser()).parseFromString) ||
 140                         (window.ActiveXObject && function(_xmlString) {
 141                     var xml_doc = new ActiveXObject("Microsoft.XMLDOM");
 142                     xml_doc.async = "false";
 143                     xml_doc.loadXML(_xmlString);
 144                     return xml_doc;
 145                 }),
 146                 resultXML;
 147                 if(!dom_parser){
 148                     return false;
 149                 }
 150                 resultXML = dom_parser.call("DOMParser" in window && (new DOMParser()) || window, xmlString, "text/xml");
 151                 return this.isXML(resultXML)?resultXML:false;
 152             }
 153         };
 154
 155
 156     ////////////////////////// PRIVATE METHODS ////////////////////////
 157
 158     /**
 159      * Initialization function. Detects if the browser supports DOM Storage
 160      * or userData behavior and behaves accordingly.
 161      */
 162     function _init(){
 163         /* Check if browser supports localStorage */
 164         var localStorageReallyWorks = false;
 165         if("localStorage" in window){
 166             try {
 167                 window.localStorage.setItem("_tmptest", "tmpval");
 168                 localStorageReallyWorks = true;
 169                 window.localStorage.removeItem("_tmptest");
 170             } catch(BogusQuotaExceededErrorOnIos5) {
 171                 // Thanks be to iOS5 Private Browsing mode which throws
 172                 // QUOTA_EXCEEDED_ERRROR DOM Exception 22.
 173             }
 174         }
 175
 176         if(localStorageReallyWorks){
 177             try {
 178                 if(window.localStorage) {
 179                     _storage_service = window.localStorage;
 180                     _backend = "localStorage";
 181                     _observer_update = _storage_service.jStorage_update;
 182                 }
 183             } catch(E3) {/* Firefox fails when touching localStorage and cookies are disabled */}
 184         }
 185         /* Check if browser supports globalStorage */
 186         else if("globalStorage" in window){
 187             try {
 188                 if(window.globalStorage) {
 189                     if(window.location.hostname == "localhost"){
 190                         _storage_service = window.globalStorage["localhost.localdomain"];
 191                     }
 192                     else{
 193                         _storage_service = window.globalStorage[window.location.hostname];
 194                     }
 195                     _backend = "globalStorage";
 196                     _observer_update = _storage_service.jStorage_update;
 197                 }
 198             } catch(E4) {/* Firefox fails when touching localStorage and cookies are disabled */}
 199         }
 200         /* Check if browser supports userData behavior */
 201         else {
 202             _storage_elm = document.createElement("link");
 203             if(_storage_elm.addBehavior){
 204
 205                 /* Use a DOM element to act as userData storage */
 206                 _storage_elm.style.behavior = "url(#default#userData)";
 207
 208                 /* userData element needs to be inserted into the DOM! */
 209                 document.getElementsByTagName("head")[0].appendChild(_storage_elm);
 210
 211                 try{
 212                     _storage_elm.load("jStorage");
 213                 }catch(E){
 214                     // try to reset cache
 215                     _storage_elm.setAttribute("jStorage", "{}");
 216                     _storage_elm.save("jStorage");
 217                     _storage_elm.load("jStorage");
 218                 }
 219
 220                 var data = "{}";
 221                 try{
 222                     data = _storage_elm.getAttribute("jStorage");
 223                 }catch(E5){}
 224
 225                 try{
 226                     _observer_update = _storage_elm.getAttribute("jStorage_update");
 227                 }catch(E6){}
 228
 229                 _storage_service.jStorage = data;
 230                 _backend = "userDataBehavior";
 231             }else{
 232                 _storage_elm = null;
 233                 return;
 234             }
 235         }
 236
 237         // Load data from storage
 238         _load_storage();
 239
 240         // remove dead keys
 241         _handleTTL();
 242
 243         // start listening for changes
 244         _setupObserver();
 245
 246         // initialize publish-subscribe service
 247         _handlePubSub();
 248
 249         // handle cached navigation
 250         if("addEventListener" in window){
 251             window.addEventListener("pageshow", function(event){
 252                 if(event.persisted){
 253                     _storageObserver();
 254                 }
 255             }, false);
 256         }
 257     }
 258
 259     /**
 260      * Reload data from storage when needed
 261      */
 262     function _reloadData(){
 263         var data = "{}";
 264
 265         if(_backend == "userDataBehavior"){
 266             _storage_elm.load("jStorage");
 267
 268             try{
 269                 data = _storage_elm.getAttribute("jStorage");
 270             }catch(E5){}
 271
 272             try{
 273                 _observer_update = _storage_elm.getAttribute("jStorage_update");
 274             }catch(E6){}
 275
 276             _storage_service.jStorage = data;
 277         }
 278
 279         _load_storage();
 280
 281         // remove dead keys
 282         _handleTTL();
 283
 284         _handlePubSub();
 285     }
 286
 287     /**
 288      * Sets up a storage change observer
 289      */
 290     function _setupObserver(){
 291         if(_backend == "localStorage" || _backend == "globalStorage"){
 292             if("addEventListener" in window){
 293                 window.addEventListener("storage", _storageObserver, false);
 294             }else{
 295                 document.attachEvent("onstorage", _storageObserver);
 296             }
 297         }else if(_backend == "userDataBehavior"){
 298             setInterval(_storageObserver, 1000);
 299         }
 300     }
 301
 302     /**
 303      * Fired on any kind of data change, needs to check if anything has
 304      * really been changed
 305      */
 306     function _storageObserver(){
 307         var updateTime;
 308         // cumulate change notifications with timeout
 309         clearTimeout(_observer_timeout);
 310         _observer_timeout = setTimeout(function(){
 311
 312             if(_backend == "localStorage" || _backend == "globalStorage"){
 313                 updateTime = _storage_service.jStorage_update;
 314             }else if(_backend == "userDataBehavior"){
 315                 _storage_elm.load("jStorage");
 316                 try{
 317                     updateTime = _storage_elm.getAttribute("jStorage_update");
 318                 }catch(E5){}
 319             }
 320
 321             if(updateTime && updateTime != _observer_update){
 322                 _observer_update = updateTime;
 323                 _checkUpdatedKeys();
 324             }
 325
 326         }, 25);
 327     }
 328
 329     /**
 330      * Reloads the data and checks if any keys are changed
 331      */
 332     function _checkUpdatedKeys(){
 333         var oldCrc32List = JSON.parse(JSON.stringify(_storage.__jstorage_meta.CRC32)),
 334             newCrc32List;
 335
 336         _reloadData();
 337         newCrc32List = JSON.parse(JSON.stringify(_storage.__jstorage_meta.CRC32));
 338
 339         var key,
 340             updated = [],
 341             removed = [];
 342
 343         for(key in oldCrc32List){
 344             if(oldCrc32List.hasOwnProperty(key)){
 345                 if(!newCrc32List[key]){
 346                     removed.push(key);
 347                     continue;
 348                 }
 349                 if(oldCrc32List[key] != newCrc32List[key] && String(oldCrc32List[key]).substr(0,2) == "2."){
 350                     updated.push(key);
 351                 }
 352             }
 353         }
 354
 355         for(key in newCrc32List){
 356             if(newCrc32List.hasOwnProperty(key)){
 357                 if(!oldCrc32List[key]){
 358                     updated.push(key);
 359                 }
 360             }
 361         }
 362
 363         _fireObservers(updated, "updated");
 364         _fireObservers(removed, "deleted");
 365     }
 366
 367     /**
 368      * Fires observers for updated keys
 369      *
 370      * @param {Array|String} keys Array of key names or a key
 371      * @param {String} action What happened with the value (updated, deleted, flushed)
 372      */
 373     function _fireObservers(keys, action){
 374         keys = [].concat(keys || []);
 375         if(action == "flushed"){
 376             keys = [];
 377             for(var key in _observers){
 378                 if(_observers.hasOwnProperty(key)){
 379                     keys.push(key);
 380                 }
 381             }
 382             action = "deleted";
 383         }
 384         for(var i=0, len = keys.length; i<len; i++){
 385             if(_observers[keys[i]]){
 386                 for(var j=0, jlen = _observers[keys[i]].length; j<jlen; j++){
 387                     _observers[keys[i]][j](keys[i], action);
 388                 }
 389             }
 390             if(_observers["*"]){
 391                 for(var j=0, jlen = _observers["*"].length; j<jlen; j++){
 392                     _observers["*"][j](keys[i], action);
 393                 }
 394             }
 395         }
 396     }
 397
 398     /**
 399      * Publishes key change to listeners
 400      */
 401     function _publishChange(){
 402         var updateTime = (+new Date()).toString();
 403
 404         if(_backend == "localStorage" || _backend == "globalStorage"){
 405             try {
 406                 _storage_service.jStorage_update = updateTime;
 407             } catch (E8) {
 408                 // safari private mode has been enabled after the jStorage initialization
 409                 _backend = false;
 410             }
 411         }else if(_backend == "userDataBehavior"){
 412             _storage_elm.setAttribute("jStorage_update", updateTime);
 413             _storage_elm.save("jStorage");
 414         }
 415
 416         _storageObserver();
 417     }
 418
 419     /**
 420      * Loads the data from the storage based on the supported mechanism
 421      */
 422     function _load_storage(){
 423         /* if jStorage string is retrieved, then decode it */
 424         if(_storage_service.jStorage){
 425             try{
 426                 _storage = JSON.parse(String(_storage_service.jStorage));
 427             }catch(E6){_storage_service.jStorage = "{}";}
 428         }else{
 429             _storage_service.jStorage = "{}";
 430         }
 431         _storage_size = _storage_service.jStorage?String(_storage_service.jStorage).length:0;
 432
 433         if(!_storage.__jstorage_meta){
 434             _storage.__jstorage_meta = {};
 435         }
 436         if(!_storage.__jstorage_meta.CRC32){
 437             _storage.__jstorage_meta.CRC32 = {};
 438         }
 439     }
 440
 441     /**
 442      * This functions provides the "save" mechanism to store the jStorage object
 443      */
 444     function _save(){
 445         _dropOldEvents(); // remove expired events
 446         try{
 447             _storage_service.jStorage = JSON.stringify(_storage);
 448             // If userData is used as the storage engine, additional
 449             if(_storage_elm) {
 450                 _storage_elm.setAttribute("jStorage",_storage_service.jStorage);
 451                 _storage_elm.save("jStorage");
 452             }
 453             _storage_size = _storage_service.jStorage?String(_storage_service.jStorage).length:0;
 454         }catch(E7){/* probably cache is full, nothing is saved this way*/}
 455     }
 456
 457     /**
 458      * Function checks if a key is set and is string or numberic
 459      *
 460      * @param {String} key Key name
 461      */
 462     function _checkKey(key){
 463         if(typeof key != "string" && typeof key != "number"){
 464             throw new TypeError("Key name must be string or numeric");
 465         }
 466         if(key == "__jstorage_meta"){
 467             throw new TypeError("Reserved key name");
 468         }
 469         return true;
 470     }
 471
 472     /**
 473      * Removes expired keys
 474      */
 475     function _handleTTL(){
 476         var curtime, i, TTL, CRC32, nextExpire = Infinity, changed = false, deleted = [];
 477
 478         clearTimeout(_ttl_timeout);
 479
 480         if(!_storage.__jstorage_meta || typeof _storage.__jstorage_meta.TTL != "object"){
 481             // nothing to do here
 482             return;
 483         }
 484
 485         curtime = +new Date();
 486         TTL = _storage.__jstorage_meta.TTL;
 487
 488         CRC32 = _storage.__jstorage_meta.CRC32;
 489         for(i in TTL){
 490             if(TTL.hasOwnProperty(i)){
 491                 if(TTL[i] <= curtime){
 492                     delete TTL[i];
 493                     delete CRC32[i];
 494                     delete _storage[i];
 495                     changed = true;
 496                     deleted.push(i);
 497                 }else if(TTL[i] < nextExpire){
 498                     nextExpire = TTL[i];
 499                 }
 500             }
 501         }
 502
 503         // set next check
 504         if(nextExpire != Infinity){
 505             _ttl_timeout = setTimeout(Math.min(_handleTTL, nextExpire - curtime, 0x7FFFFFFF));
 506         }
 507
 508         // save changes
 509         if(changed){
 510             _save();
 511             _publishChange();
 512             _fireObservers(deleted, "deleted");
 513         }
 514     }
 515
 516     /**
 517      * Checks if there's any events on hold to be fired to listeners
 518      */
 519     function _handlePubSub(){
 520         var i, len;
 521         if(!_storage.__jstorage_meta.PubSub){
 522             return;
 523         }
 524         var pubelm,
 525             _pubsubCurrent = _pubsub_last;
 526
 527         for(i=len=_storage.__jstorage_meta.PubSub.length-1; i>=0; i--){
 528             pubelm = _storage.__jstorage_meta.PubSub[i];
 529             if(pubelm[0] > _pubsub_last){
 530                 _pubsubCurrent = pubelm[0];
 531                 _fireSubscribers(pubelm[1], pubelm[2]);
 532             }
 533         }
 534
 535         _pubsub_last = _pubsubCurrent;
 536     }
 537
 538     /**
 539      * Fires all subscriber listeners for a pubsub channel
 540      *
 541      * @param {String} channel Channel name
 542      * @param {Mixed} payload Payload data to deliver
 543      */
 544     function _fireSubscribers(channel, payload){
 545         if(_pubsub_observers[channel]){
 546             for(var i=0, len = _pubsub_observers[channel].length; i<len; i++){
 547                 // send immutable data that can't be modified by listeners
 548                 try{
 549                     _pubsub_observers[channel][i](channel, JSON.parse(JSON.stringify(payload)));
 550                 }catch(E){};
 551             }
 552         }
 553     }
 554
 555     /**
 556      * Remove old events from the publish stream (at least 2sec old)
 557      */
 558     function _dropOldEvents(){
 559         if(!_storage.__jstorage_meta.PubSub){
 560             return;
 561         }
 562
 563         var retire = +new Date() - 2000;
 564
 565         for(var i=0, len = _storage.__jstorage_meta.PubSub.length; i<len; i++){
 566             if(_storage.__jstorage_meta.PubSub[i][0] <= retire){
 567                 // deleteCount is needed for IE6
 568                 _storage.__jstorage_meta.PubSub.splice(i, _storage.__jstorage_meta.PubSub.length - i);
 569                 break;
 570             }
 571         }
 572
 573         if(!_storage.__jstorage_meta.PubSub.length){
 574             delete _storage.__jstorage_meta.PubSub;
 575         }
 576
 577     }
 578
 579     /**
 580      * Publish payload to a channel
 581      *
 582      * @param {String} channel Channel name
 583      * @param {Mixed} payload Payload to send to the subscribers
 584      */
 585     function _publish(channel, payload){
 586         if(!_storage.__jstorage_meta){
 587             _storage.__jstorage_meta = {};
 588         }
 589         if(!_storage.__jstorage_meta.PubSub){
 590             _storage.__jstorage_meta.PubSub = [];
 591         }
 592
 593         _storage.__jstorage_meta.PubSub.unshift([+new Date, channel, payload]);
 594
 595         _save();
 596         _publishChange();
 597     }
 598
 599
 600     /**
 601      * JS Implementation of MurmurHash2
 602      *
 603      *  SOURCE: https://github.com/garycourt/murmurhash-js (MIT licensed)
 604      *
 605      * @author <a href="mailto:gary.court@gmail.com">Gary Court</a>
 606      * @see http://github.com/garycourt/murmurhash-js
 607      * @author <a href="mailto:aappleby@gmail.com">Austin Appleby</a>
 608      * @see http://sites.google.com/site/murmurhash/
 609      *
 610      * @param {string} str ASCII only
 611      * @param {number} seed Positive integer only
 612      * @return {number} 32-bit positive integer hash
 613      */
 614
 615     function murmurhash2_32_gc(str, seed) {
 616         var
 617             l = str.length,
 618             h = seed ^ l,
 619             i = 0,
 620             k;
 621
 622         while (l >= 4) {
 623             k =
 624                 ((str.charCodeAt(i) & 0xff)) |
 625                 ((str.charCodeAt(++i) & 0xff) << 8) |
 626                 ((str.charCodeAt(++i) & 0xff) << 16) |
 627                 ((str.charCodeAt(++i) & 0xff) << 24);
 628
 629             k = (((k & 0xffff) * 0x5bd1e995) + ((((k >>> 16) * 0x5bd1e995) & 0xffff) << 16));
 630             k ^= k >>> 24;
 631             k = (((k & 0xffff) * 0x5bd1e995) + ((((k >>> 16) * 0x5bd1e995) & 0xffff) << 16));
 632
 633             h = (((h & 0xffff) * 0x5bd1e995) + ((((h >>> 16) * 0x5bd1e995) & 0xffff) << 16)) ^ k;
 634
 635             l -= 4;
 636             ++i;
 637         }
 638
 639         switch (l) {
 640             case 3: h ^= (str.charCodeAt(i + 2) & 0xff) << 16;
 641             case 2: h ^= (str.charCodeAt(i + 1) & 0xff) << 8;
 642             case 1: h ^= (str.charCodeAt(i) & 0xff);
 643                 h = (((h & 0xffff) * 0x5bd1e995) + ((((h >>> 16) * 0x5bd1e995) & 0xffff) << 16));
 644         }
 645
 646         h ^= h >>> 13;
 647         h = (((h & 0xffff) * 0x5bd1e995) + ((((h >>> 16) * 0x5bd1e995) & 0xffff) << 16));
 648         h ^= h >>> 15;
 649
 650         return h >>> 0;
 651     }
 652
 653     ////////////////////////// PUBLIC INTERFACE /////////////////////////
 654
 655     $.jStorage = {
 656         /* Version number */
 657         version: JSTORAGE_VERSION,
 658
 659         /**
 660          * Sets a key's value.
 661          *
 662          * @param {String} key Key to set. If this value is not set or not
 663          *              a string an exception is raised.
 664          * @param {Mixed} value Value to set. This can be any value that is JSON
 665          *              compatible (Numbers, Strings, Objects etc.).
 666          * @param {Object} [options] - possible options to use
 667          * @param {Number} [options.TTL] - optional TTL value, in milliseconds
 668          * @return {Mixed} the used value
 669          */
 670         set: function(key, value, options){
 671             _checkKey(key);
 672
 673             options = options || {};
 674
 675             // undefined values are deleted automatically
 676             if(typeof value == "undefined"){
 677                 this.deleteKey(key);
 678                 return value;
 679             }
 680
 681             if(_XMLService.isXML(value)){
 682                 value = {_is_xml:true,xml:_XMLService.encode(value)};
 683             }else if(typeof value == "function"){
 684                 return undefined; // functions can't be saved!
 685             }else if(value && typeof value == "object"){
 686                 // clone the object before saving to _storage tree
 687                 value = JSON.parse(JSON.stringify(value));
 688             }
 689
 690             _storage[key] = value;
 691
 692             _storage.__jstorage_meta.CRC32[key] = "2." + murmurhash2_32_gc(JSON.stringify(value), 0x9747b28c);
 693
 694             this.setTTL(key, options.TTL || 0); // also handles saving and _publishChange
 695
 696             _fireObservers(key, "updated");
 697             return value;
 698         },
 699
 700         /**
 701          * Looks up a key in cache
 702          *
 703          * @param {String} key - Key to look up.
 704          * @param {mixed} def - Default value to return, if key didn't exist.
 705          * @return {Mixed} the key value, default value or null
 706          */
 707         get: function(key, def){
 708             _checkKey(key);
 709             if(key in _storage){
 710                 if(_storage[key] && typeof _storage[key] == "object" && _storage[key]._is_xml) {
 711                     return _XMLService.decode(_storage[key].xml);
 712                 }else{
 713                     return _storage[key];
 714                 }
 715             }
 716             return typeof(def) == "undefined" ? null : def;
 717         },
 718
 719         /**
 720          * Deletes a key from cache.
 721          *
 722          * @param {String} key - Key to delete.
 723          * @return {Boolean} true if key existed or false if it didn't
 724          */
 725         deleteKey: function(key){
 726             _checkKey(key);
 727             if(key in _storage){
 728                 delete _storage[key];
 729                 // remove from TTL list
 730                 if(typeof _storage.__jstorage_meta.TTL == "object" &&
 731                   key in _storage.__jstorage_meta.TTL){
 732                     delete _storage.__jstorage_meta.TTL[key];
 733                 }
 734
 735                 delete _storage.__jstorage_meta.CRC32[key];
 736
 737                 _save();
 738                 _publishChange();
 739                 _fireObservers(key, "deleted");
 740                 return true;
 741             }
 742             return false;
 743         },
 744
 745         /**
 746          * Sets a TTL for a key, or remove it if ttl value is 0 or below
 747          *
 748          * @param {String} key - key to set the TTL for
 749          * @param {Number} ttl - TTL timeout in milliseconds
 750          * @return {Boolean} true if key existed or false if it didn't
 751          */
 752         setTTL: function(key, ttl){
 753             var curtime = +new Date();
 754             _checkKey(key);
 755             ttl = Number(ttl) || 0;
 756             if(key in _storage){
 757
 758                 if(!_storage.__jstorage_meta.TTL){
 759                     _storage.__jstorage_meta.TTL = {};
 760                 }
 761
 762                 // Set TTL value for the key
 763                 if(ttl>0){
 764                     _storage.__jstorage_meta.TTL[key] = curtime + ttl;
 765                 }else{
 766                     delete _storage.__jstorage_meta.TTL[key];
 767                 }
 768
 769                 _save();
 770
 771                 _handleTTL();
 772
 773                 _publishChange();
 774                 return true;
 775             }
 776             return false;
 777         },
 778
 779         /**
 780          * Gets remaining TTL (in milliseconds) for a key or 0 when no TTL has been set
 781          *
 782          * @param {String} key Key to check
 783          * @return {Number} Remaining TTL in milliseconds
 784          */
 785         getTTL: function(key){
 786             var curtime = +new Date(), ttl;
 787             _checkKey(key);
 788             if(key in _storage && _storage.__jstorage_meta.TTL && _storage.__jstorage_meta.TTL[key]){
 789                 ttl = _storage.__jstorage_meta.TTL[key] - curtime;
 790                 return ttl || 0;
 791             }
 792             return 0;
 793         },
 794
 795         /**
 796          * Deletes everything in cache.
 797          *
 798          * @return {Boolean} Always true
 799          */
 800         flush: function(){
 801             _storage = {__jstorage_meta:{CRC32:{}}};
 802             _save();
 803             _publishChange();
 804             _fireObservers(null, "flushed");
 805             return true;
 806         },
 807
 808         /**
 809          * Returns a read-only copy of _storage
 810          *
 811          * @return {Object} Read-only copy of _storage
 812         */
 813         storageObj: function(){
 814             function F() {}
 815             F.prototype = _storage;
 816             return new F();
 817         },
 818
 819         /**
 820          * Returns an index of all used keys as an array
 821          * ["key1", "key2",.."keyN"]
 822          *
 823          * @return {Array} Used keys
 824         */
 825         index: function(){
 826             var index = [], i;
 827             for(i in _storage){
 828                 if(_storage.hasOwnProperty(i) && i != "__jstorage_meta"){
 829                     index.push(i);
 830                 }
 831             }
 832             return index;
 833         },
 834
 835         /**
 836          * How much space in bytes does the storage take?
 837          *
 838          * @return {Number} Storage size in chars (not the same as in bytes,
 839          *                  since some chars may take several bytes)
 840          */
 841         storageSize: function(){
 842             return _storage_size;
 843         },
 844
 845         /**
 846          * Which backend is currently in use?
 847          *
 848          * @return {String} Backend name
 849          */
 850         currentBackend: function(){
 851             return _backend;
 852         },
 853
 854         /**
 855          * Test if storage is available
 856          *
 857          * @return {Boolean} True if storage can be used
 858          */
 859         storageAvailable: function(){
 860             return !!_backend;
 861         },
 862
 863         /**
 864          * Register change listeners
 865          *
 866          * @param {String} key Key name
 867          * @param {Function} callback Function to run when the key changes
 868          */
 869         listenKeyChange: function(key, callback){
 870             _checkKey(key);
 871             if(!_observers[key]){
 872                 _observers[key] = [];
 873             }
 874             _observers[key].push(callback);
 875         },
 876
 877         /**
 878          * Remove change listeners
 879          *
 880          * @param {String} key Key name to unregister listeners against
 881          * @param {Function} [callback] If set, unregister the callback, if not - unregister all
 882          */
 883         stopListening: function(key, callback){
 884             _checkKey(key);
 885
 886             if(!_observers[key]){
 887                 return;
 888             }
 889
 890             if(!callback){
 891                 delete _observers[key];
 892                 return;
 893             }
 894
 895             for(var i = _observers[key].length - 1; i>=0; i--){
 896                 if(_observers[key][i] == callback){
 897                     _observers[key].splice(i,1);
 898                 }
 899             }
 900         },
 901
 902         /**
 903          * Subscribe to a Publish/Subscribe event stream
 904          *
 905          * @param {String} channel Channel name
 906          * @param {Function} callback Function to run when the something is published to the channel
 907          */
 908         subscribe: function(channel, callback){
 909             channel = (channel || "").toString();
 910             if(!channel){
 911                 throw new TypeError("Channel not defined");
 912             }
 913             if(!_pubsub_observers[channel]){
 914                 _pubsub_observers[channel] = [];
 915             }
 916             _pubsub_observers[channel].push(callback);
 917         },
 918
 919         /**
 920          * Publish data to an event stream
 921          *
 922          * @param {String} channel Channel name
 923          * @param {Mixed} payload Payload to deliver
 924          */
 925         publish: function(channel, payload){
 926             channel = (channel || "").toString();
 927             if(!channel){
 928                 throw new TypeError("Channel not defined");
 929             }
 930
 931             _publish(channel, payload);
 932         },
 933
 934         /**
 935          * Reloads the data from browser storage
 936          */
 937         reInit: function(){
 938             _reloadData();
 939         },
 940
 941         /**
 942          * Removes reference from global objects and saves it as jStorage
 943          *
 944          * @param {Boolean} option if needed to save object as simple "jStorage" in windows context
 945          */
 946          noConflict: function( saveInGlobal ) {
 947             delete window.$.jStorage
 948
 949             if ( saveInGlobal ) {
 950                 window.jStorage = this;
 951             }
 952
 953             return this;
 954          }
 955     };
 956
 957     // Initialize jStorage
 958     _init();
 959
 960 })();