include/javascript/yui/build/connection/connection_core.js

   1 /*
   2 Copyright (c) 2009, Yahoo! Inc. All rights reserved.
   3 Code licensed under the BSD License:
   4 http://developer.yahoo.net/yui/license.txt
   5 version: 2.8.0r4
   6 */
   7 /**
   8  * The Connection Manager provides a simplified interface to the XMLHttpRequest
   9  * object.  It handles cross-browser instantiantion of XMLHttpRequest, negotiates the
  10  * interactive states and server response, returning the results to a pre-defined
  11  * callback you create.
  12  *
  13  * @namespace YAHOO.util
  14  * @module connection
  15  * @requires yahoo
  16  * @requires event
  17  */
  18
  19 /**
  20  * The Connection Manager singleton provides methods for creating and managing
  21  * asynchronous transactions.
  22  *
  23  * @class Connect
  24  */
  25
  26 YAHOO.util.Connect =
  27 {
  28   /**
  29    * @description Array of MSFT ActiveX ids for XMLHttpRequest.
  30    * @property _msxml_progid
  31    * @private
  32    * @static
  33    * @type array
  34    */
  35         _msxml_progid:[
  36                 'Microsoft.XMLHTTP',
  37                 'MSXML2.XMLHTTP.3.0',
  38                 'MSXML2.XMLHTTP'
  39                 ],
  40
  41   /**
  42    * @description Object literal of HTTP header(s)
  43    * @property _http_header
  44    * @private
  45    * @static
  46    * @type object
  47    */
  48         _http_headers:{},
  49
  50   /**
  51    * @description Determines if HTTP headers are set.
  52    * @property _has_http_headers
  53    * @private
  54    * @static
  55    * @type boolean
  56    */
  57         _has_http_headers:false,
  58
  59  /**
  60   * @description Determines if a default header of
  61   * Content-Type of 'application/x-www-form-urlencoded'
  62   * will be added to any client HTTP headers sent for POST
  63   * transactions.
  64   * @property _use_default_post_header
  65   * @private
  66   * @static
  67   * @type boolean
  68   */
  69     _use_default_post_header:true,
  70
  71  /**
  72   * @description The default header used for POST transactions.
  73   * @property _default_post_header
  74   * @private
  75   * @static
  76   * @type boolean
  77   */
  78     _default_post_header:'application/x-www-form-urlencoded; charset=UTF-8',
  79
  80  /**
  81   * @description The default header used for transactions involving the
  82   * use of HTML forms.
  83   * @property _default_form_header
  84   * @private
  85   * @static
  86   * @type boolean
  87   */
  88     _default_form_header:'application/x-www-form-urlencoded',
  89
  90  /**
  91   * @description Determines if a default header of
  92   * 'X-Requested-With: XMLHttpRequest'
  93   * will be added to each transaction.
  94   * @property _use_default_xhr_header
  95   * @private
  96   * @static
  97   * @type boolean
  98   */
  99     _use_default_xhr_header:true,
 100
 101  /**
 102   * @description The default header value for the label
 103   * "X-Requested-With".  This is sent with each
 104   * transaction, by default, to identify the
 105   * request as being made by YUI Connection Manager.
 106   * @property _default_xhr_header
 107   * @private
 108   * @static
 109   * @type boolean
 110   */
 111     _default_xhr_header:'XMLHttpRequest',
 112
 113  /**
 114   * @description Determines if custom, default headers
 115   * are set for each transaction.
 116   * @property _has_default_header
 117   * @private
 118   * @static
 119   * @type boolean
 120   */
 121     _has_default_headers:true,
 122
 123  /**
 124   * @description Determines if custom, default headers
 125   * are set for each transaction.
 126   * @property _has_default_header
 127   * @private
 128   * @static
 129   * @type boolean
 130   */
 131     _default_headers:{},
 132
 133  /**
 134   * @description Collection of polling references to the polling mechanism in handleReadyState.
 135   * @property _poll
 136   * @private
 137   * @static
 138   * @type object
 139   */
 140     _poll:{},
 141
 142  /**
 143   * @description Queue of timeout values for each transaction callback with a defined timeout value.
 144   * @property _timeOut
 145   * @private
 146   * @static
 147   * @type object
 148   */
 149     _timeOut:{},
 150
 151   /**
 152    * @description The polling frequency, in milliseconds, for HandleReadyState.
 153    * when attempting to determine a transaction's XHR readyState.
 154    * The default is 50 milliseconds.
 155    * @property _polling_interval
 156    * @private
 157    * @static
 158    * @type int
 159    */
 160      _polling_interval:50,
 161
 162   /**
 163    * @description A transaction counter that increments the transaction id for each transaction.
 164    * @property _transaction_id
 165    * @private
 166    * @static
 167    * @type int
 168    */
 169      _transaction_id:0,
 170
 171   /**
 172    * @description Custom event that fires at the start of a transaction
 173    * @property startEvent
 174    * @private
 175    * @static
 176    * @type CustomEvent
 177    */
 178         startEvent: new YAHOO.util.CustomEvent('start'),
 179
 180   /**
 181    * @description Custom event that fires when a transaction response has completed.
 182    * @property completeEvent
 183    * @private
 184    * @static
 185    * @type CustomEvent
 186    */
 187         completeEvent: new YAHOO.util.CustomEvent('complete'),
 188
 189   /**
 190    * @description Custom event that fires when handleTransactionResponse() determines a
 191    * response in the HTTP 2xx range.
 192    * @property successEvent
 193    * @private
 194    * @static
 195    * @type CustomEvent
 196    */
 197         successEvent: new YAHOO.util.CustomEvent('success'),
 198
 199   /**
 200    * @description Custom event that fires when handleTransactionResponse() determines a
 201    * response in the HTTP 4xx/5xx range.
 202    * @property failureEvent
 203    * @private
 204    * @static
 205    * @type CustomEvent
 206    */
 207         failureEvent: new YAHOO.util.CustomEvent('failure'),
 208
 209   /**
 210    * @description Custom event that fires when a transaction is successfully aborted.
 211    * @property abortEvent
 212    * @private
 213    * @static
 214    * @type CustomEvent
 215    */
 216         abortEvent: new YAHOO.util.CustomEvent('abort'),
 217
 218   /**
 219    * @description A reference table that maps callback custom events members to its specific
 220    * event name.
 221    * @property _customEvents
 222    * @private
 223    * @static
 224    * @type object
 225    */
 226         _customEvents:
 227         {
 228                 onStart:['startEvent', 'start'],
 229                 onComplete:['completeEvent', 'complete'],
 230                 onSuccess:['successEvent', 'success'],
 231                 onFailure:['failureEvent', 'failure'],
 232                 onUpload:['uploadEvent', 'upload'],
 233                 onAbort:['abortEvent', 'abort']
 234         },
 235
 236   /**
 237    * @description Member to add an ActiveX id to the existing xml_progid array.
 238    * In the event(unlikely) a new ActiveX id is introduced, it can be added
 239    * without internal code modifications.
 240    * @method setProgId
 241    * @public
 242    * @static
 243    * @param {string} id The ActiveX id to be added to initialize the XHR object.
 244    * @return void
 245    */
 246         setProgId:function(id)
 247         {
 248                 this._msxml_progid.unshift(id);
 249         },
 250
 251   /**
 252    * @description Member to override the default POST header.
 253    * @method setDefaultPostHeader
 254    * @public
 255    * @static
 256    * @param {boolean} b Set and use default header - true or false .
 257    * @return void
 258    */
 259         setDefaultPostHeader:function(b)
 260         {
 261                 if(typeof b == 'string'){
 262                         this._default_post_header = b;
 263                 }
 264                 else if(typeof b == 'boolean'){
 265                         this._use_default_post_header = b;
 266                 }
 267         },
 268
 269   /**
 270    * @description Member to override the default transaction header..
 271    * @method setDefaultXhrHeader
 272    * @public
 273    * @static
 274    * @param {boolean} b Set and use default header - true or false .
 275    * @return void
 276    */
 277         setDefaultXhrHeader:function(b)
 278         {
 279                 if(typeof b == 'string'){
 280                         this._default_xhr_header = b;
 281                 }
 282                 else{
 283                         this._use_default_xhr_header = b;
 284                 }
 285         },
 286
 287   /**
 288    * @description Member to modify the default polling interval.
 289    * @method setPollingInterval
 290    * @public
 291    * @static
 292    * @param {int} i The polling interval in milliseconds.
 293    * @return void
 294    */
 295         setPollingInterval:function(i)
 296         {
 297                 if(typeof i == 'number' && isFinite(i)){
 298                         this._polling_interval = i;
 299                 }
 300         },
 301
 302   /**
 303    * @description Instantiates a XMLHttpRequest object and returns an object with two properties:
 304    * the XMLHttpRequest instance and the transaction id.
 305    * @method createXhrObject
 306    * @private
 307    * @static
 308    * @param {int} transactionId Property containing the transaction id for this transaction.
 309    * @return object
 310    */
 311         createXhrObject:function(transactionId)
 312         {
 313                 var obj,http,i;
 314                 try
 315                 {
 316                         // Instantiates XMLHttpRequest in non-IE browsers and assigns to http.
 317                         http = new XMLHttpRequest();
 318                         //  Object literal with http and tId properties
 319                         obj = { conn:http, tId:transactionId, xhr: true };
 320                 }
 321                 catch(e)
 322                 {
 323                         for(i=0; i<this._msxml_progid.length; ++i){
 324                                 try
 325                                 {
 326                                         // Instantiates XMLHttpRequest for IE and assign to http
 327                                         http = new ActiveXObject(this._msxml_progid[i]);
 328                                         //  Object literal with conn and tId properties
 329                                         obj = { conn:http, tId:transactionId, xhr: true };
 330                                         break;
 331                                 }
 332                                 catch(e1){}
 333                         }
 334                 }
 335                 finally
 336                 {
 337                         return obj;
 338                 }
 339         },
 340
 341   /**
 342    * @description This method is called by asyncRequest to create a
 343    * valid connection object for the transaction.  It also passes a
 344    * transaction id and increments the transaction id counter.
 345    * @method getConnectionObject
 346    * @private
 347    * @static
 348    * @return {object}
 349    */
 350         getConnectionObject:function(t)
 351         {
 352                 var o, tId = this._transaction_id;
 353
 354                 try
 355                 {
 356                         if(!t){
 357                                 o = this.createXhrObject(tId);
 358                         }
 359                         else{
 360                                 o = {tId:tId};
 361                                 if(t==='xdr'){
 362                                         o.conn = this._transport;
 363                                         o.xdr = true;
 364                                 }
 365                                 else if(t==='upload'){
 366                                         o.upload = true;
 367                                 }
 368                         }
 369
 370                         if(o){
 371                                 this._transaction_id++;
 372                         }
 373                 }
 374                 catch(e){}
 375                 return o;
 376         },
 377
 378   /**
 379    * @description Method for initiating an asynchronous request via the XHR object.
 380    * @method asyncRequest
 381    * @public
 382    * @static
 383    * @param {string} method HTTP transaction method
 384    * @param {string} uri Fully qualified path of resource
 385    * @param {callback} callback User-defined callback function or object
 386    * @param {string} postData POST body
 387    * @return {object} Returns the connection object
 388    */
 389         asyncRequest:function(method, uri, callback, postData)
 390         {
 391                 var o,t,args = (callback && callback.argument)?callback.argument:null;
 392
 393                 if(this._isFileUpload){
 394                         t = 'upload';
 395                 }
 396                 else if(callback.xdr){
 397                         t = 'xdr';
 398                 }
 399
 400                 o = this.getConnectionObject(t);
 401                 if(!o){
 402                         return null;
 403                 }
 404                 else{
 405
 406                         // Intialize any transaction-specific custom events, if provided.
 407                         if(callback && callback.customevents){
 408                                 this.initCustomEvents(o, callback);
 409                         }
 410
 411                         if(this._isFormSubmit){
 412                                 if(this._isFileUpload){
 413                                         this.uploadFile(o, callback, uri, postData);
 414                                         return o;
 415                                 }
 416
 417                                 // If the specified HTTP method is GET, setForm() will return an
 418                                 // encoded string that is concatenated to the uri to
 419                                 // create a querystring.
 420                                 if(method.toUpperCase() == 'GET'){
 421                                         if(this._sFormData.length !== 0){
 422                                                 // If the URI already contains a querystring, append an ampersand
 423                                                 // and then concatenate _sFormData to the URI.
 424                                                 uri += ((uri.indexOf('?') == -1)?'?':'&') + this._sFormData;
 425                                         }
 426                                 }
 427                                 else if(method.toUpperCase() == 'POST'){
 428                                         // If POST data exist in addition to the HTML form data,
 429                                         // it will be concatenated to the form data.
 430                                         postData = postData?this._sFormData + "&" + postData:this._sFormData;
 431                                 }
 432                         }
 433
 434                         if(method.toUpperCase() == 'GET' && (callback && callback.cache === false)){
 435                                 // If callback.cache is defined and set to false, a
 436                                 // timestamp value will be added to the querystring.
 437                                 uri += ((uri.indexOf('?') == -1)?'?':'&') + "rnd=" + new Date().valueOf().toString();
 438                         }
 439
 440                         // Each transaction will automatically include a custom header of
 441                         // "X-Requested-With: XMLHttpRequest" to identify the request as
 442                         // having originated from Connection Manager.
 443                         if(this._use_default_xhr_header){
 444                                 if(!this._default_headers['X-Requested-With']){
 445                                         this.initHeader('X-Requested-With', this._default_xhr_header, true);
 446                                 }
 447                         }
 448
 449                         //If the transaction method is POST and the POST header value is set to true
 450                         //or a custom value, initalize the Content-Type header to this value.
 451                         if((method.toUpperCase() === 'POST' && this._use_default_post_header) && this._isFormSubmit === false){
 452                                 this.initHeader('Content-Type', this._default_post_header);
 453                         }
 454
 455                         if(o.xdr){
 456                                 this.xdr(o, method, uri, callback, postData);
 457                                 return o;
 458                         }
 459
 460                         o.conn.open(method, uri, true);
 461                         //Initialize all default and custom HTTP headers,
 462                         if(this._has_default_headers || this._has_http_headers){
 463                                 this.setHeader(o);
 464                         }
 465
 466                         this.handleReadyState(o, callback);
 467                         o.conn.send(postData || '');
 468
 469                         // Reset the HTML form data and state properties as
 470                         // soon as the data are submitted.
 471                         if(this._isFormSubmit === true){
 472                                 this.resetFormState();
 473                         }
 474
 475                         // Fire global custom event -- startEvent
 476                         this.startEvent.fire(o, args);
 477
 478                         if(o.startEvent){
 479                                 // Fire transaction custom event -- startEvent
 480                                 o.startEvent.fire(o, args);
 481                         }
 482
 483                         return o;
 484                 }
 485         },
 486
 487   /**
 488    * @description This method creates and subscribes custom events,
 489    * specific to each transaction
 490    * @method initCustomEvents
 491    * @private
 492    * @static
 493    * @param {object} o The connection object
 494    * @param {callback} callback The user-defined callback object
 495    * @return {void}
 496    */
 497         initCustomEvents:function(o, callback)
 498         {
 499                 var prop;
 500                 // Enumerate through callback.customevents members and bind/subscribe
 501                 // events that match in the _customEvents table.
 502                 for(prop in callback.customevents){
 503                         if(this._customEvents[prop][0]){
 504                                 // Create the custom event
 505                                 o[this._customEvents[prop][0]] = new YAHOO.util.CustomEvent(this._customEvents[prop][1], (callback.scope)?callback.scope:null);
 506
 507                                 // Subscribe the custom event
 508                                 o[this._customEvents[prop][0]].subscribe(callback.customevents[prop]);
 509                         }
 510                 }
 511         },
 512
 513   /**
 514    * @description This method serves as a timer that polls the XHR object's readyState
 515    * property during a transaction, instead of binding a callback to the
 516    * onreadystatechange event.  Upon readyState 4, handleTransactionResponse
 517    * will process the response, and the timer will be cleared.
 518    * @method handleReadyState
 519    * @private
 520    * @static
 521    * @param {object} o The connection object
 522    * @param {callback} callback The user-defined callback object
 523    * @return {void}
 524    */
 525
 526     handleReadyState:function(o, callback)
 527
 528     {
 529                 var oConn = this,
 530                         args = (callback && callback.argument)?callback.argument:null;
 531
 532                 if(callback && callback.timeout){
 533                         this._timeOut[o.tId] = window.setTimeout(function(){ oConn.abort(o, callback, true); }, callback.timeout);
 534                 }
 535
 536                 this._poll[o.tId] = window.setInterval(
 537                         function(){
 538                                 if(o.conn && o.conn.readyState === 4){
 539
 540                                         // Clear the polling interval for the transaction
 541                                         // and remove the reference from _poll.
 542                                         window.clearInterval(oConn._poll[o.tId]);
 543                                         delete oConn._poll[o.tId];
 544
 545                                         if(callback && callback.timeout){
 546                                                 window.clearTimeout(oConn._timeOut[o.tId]);
 547                                                 delete oConn._timeOut[o.tId];
 548                                         }
 549
 550                                         // Fire global custom event -- completeEvent
 551                                         oConn.completeEvent.fire(o, args);
 552
 553                                         if(o.completeEvent){
 554                                                 // Fire transaction custom event -- completeEvent
 555                                                 o.completeEvent.fire(o, args);
 556                                         }
 557
 558                                         oConn.handleTransactionResponse(o, callback);
 559                                 }
 560                         }
 561                 ,this._polling_interval);
 562     },
 563
 564   /**
 565    * @description This method attempts to interpret the server response and
 566    * determine whether the transaction was successful, or if an error or
 567    * exception was encountered.
 568    * @method handleTransactionResponse
 569    * @private
 570    * @static
 571    * @param {object} o The connection object
 572    * @param {object} callback The user-defined callback object
 573    * @param {boolean} isAbort Determines if the transaction was terminated via abort().
 574    * @return {void}
 575    */
 576     handleTransactionResponse:function(o, callback, isAbort)
 577     {
 578                 var httpStatus, responseObject,
 579                         args = (callback && callback.argument)?callback.argument:null,
 580                         xdrS = (o.r && o.r.statusText === 'xdr:success')?true:false,
 581                         xdrF = (o.r && o.r.statusText === 'xdr:failure')?true:false,
 582                         xdrA = isAbort;
 583
 584                 try
 585                 {
 586                         if((o.conn.status !== undefined && o.conn.status !== 0) || xdrS){
 587                                 // XDR requests will not have HTTP status defined. The
 588                                 // statusText property will define the response status
 589                                 // set by the Flash transport.
 590                                 httpStatus = o.conn.status;
 591                         }
 592                         else if(xdrF && !xdrA){
 593                                 // Set XDR transaction failure to a status of 0, which
 594                                 // resolves as an HTTP failure, instead of an exception.
 595                                 httpStatus = 0;
 596                         }
 597                         else{
 598                                 httpStatus = 13030;
 599                         }
 600                 }
 601                 catch(e){
 602
 603                          // 13030 is a custom code to indicate the condition -- in Mozilla/FF --
 604                          // when the XHR object's status and statusText properties are
 605                          // unavailable, and a query attempt throws an exception.
 606                         httpStatus = 13030;
 607                 }
 608
 609                 if((httpStatus >= 200 && httpStatus < 300) || httpStatus === 1223 || xdrS){
 610                         responseObject = o.xdr ? o.r : this.createResponseObject(o, args);
 611                         if(callback && callback.success){
 612                                 if(!callback.scope){
 613                                         callback.success(responseObject);
 614                                 }
 615                                 else{
 616                                         // If a scope property is defined, the callback will be fired from
 617                                         // the context of the object.
 618                                         callback.success.apply(callback.scope, [responseObject]);
 619                                 }
 620                         }
 621
 622                         // Fire global custom event -- successEvent
 623                         this.successEvent.fire(responseObject);
 624
 625                         if(o.successEvent){
 626                                 // Fire transaction custom event -- successEvent
 627                                 o.successEvent.fire(responseObject);
 628                         }
 629                 }
 630                 else{
 631                         switch(httpStatus){
 632                                 // The following cases are wininet.dll error codes that may be encountered.
 633                                 case 12002: // Server timeout
 634                                 case 12029: // 12029 to 12031 correspond to dropped connections.
 635                                 case 12030:
 636                                 case 12031:
 637                                 case 12152: // Connection closed by server.
 638                                 case 13030: // See above comments for variable status.
 639                                         // XDR transactions will not resolve to this case, since the
 640                                         // response object is already built in the xdr response.
 641                                         responseObject = this.createExceptionObject(o.tId, args, (isAbort?isAbort:false));
 642                                         if(callback && callback.failure){
 643                                                 if(!callback.scope){
 644                                                         callback.failure(responseObject);
 645                                                 }
 646                                                 else{
 647                                                         callback.failure.apply(callback.scope, [responseObject]);
 648                                                 }
 649                                         }
 650
 651                                         break;
 652                                 default:
 653                                         responseObject = (o.xdr) ? o.response : this.createResponseObject(o, args);
 654                                         if(callback && callback.failure){
 655                                                 if(!callback.scope){
 656                                                         callback.failure(responseObject);
 657                                                 }
 658                                                 else{
 659                                                         callback.failure.apply(callback.scope, [responseObject]);
 660                                                 }
 661                                         }
 662                         }
 663
 664                         // Fire global custom event -- failureEvent
 665                         this.failureEvent.fire(responseObject);
 666
 667                         if(o.failureEvent){
 668                                 // Fire transaction custom event -- failureEvent
 669                                 o.failureEvent.fire(responseObject);
 670                         }
 671
 672                 }
 673
 674                 this.releaseObject(o);
 675                 responseObject = null;
 676     },
 677
 678   /**
 679    * @description This method evaluates the server response, creates and returns the results via
 680    * its properties.  Success and failure cases will differ in the response
 681    * object's property values.
 682    * @method createResponseObject
 683    * @private
 684    * @static
 685    * @param {object} o The connection object
 686    * @param {callbackArg} callbackArg The user-defined argument or arguments to be passed to the callback
 687    * @return {object}
 688    */
 689     createResponseObject:function(o, callbackArg)
 690     {
 691                 var obj = {}, headerObj = {},
 692                         i, headerStr, header, delimitPos;
 693
 694                 try
 695                 {
 696                         headerStr = o.conn.getAllResponseHeaders();
 697                         header = headerStr.split('\n');
 698                         for(i=0; i<header.length; i++){
 699                                 delimitPos = header[i].indexOf(':');
 700                                 if(delimitPos != -1){
 701                                         headerObj[header[i].substring(0,delimitPos)] = YAHOO.lang.trim(header[i].substring(delimitPos+2));
 702                                 }
 703                         }
 704                 }
 705                 catch(e){}
 706
 707                 obj.tId = o.tId;
 708                 // Normalize IE's response to HTTP 204 when Win error 1223.
 709                 obj.status = (o.conn.status == 1223)?204:o.conn.status;
 710                 // Normalize IE's statusText to "No Content" instead of "Unknown".
 711                 obj.statusText = (o.conn.status == 1223)?"No Content":o.conn.statusText;
 712                 obj.getResponseHeader = headerObj;
 713                 obj.getAllResponseHeaders = headerStr;
 714                 obj.responseText = o.conn.responseText;
 715                 obj.responseXML = o.conn.responseXML;
 716
 717                 if(callbackArg){
 718                         obj.argument = callbackArg;
 719                 }
 720
 721                 return obj;
 722     },
 723
 724   /**
 725    * @description If a transaction cannot be completed due to dropped or closed connections,
 726    * there may be not be enough information to build a full response object.
 727    * The failure callback will be fired and this specific condition can be identified
 728    * by a status property value of 0.
 729    *
 730    * If an abort was successful, the status property will report a value of -1.
 731    *
 732    * @method createExceptionObject
 733    * @private
 734    * @static
 735    * @param {int} tId The Transaction Id
 736    * @param {callbackArg} callbackArg The user-defined argument or arguments to be passed to the callback
 737    * @param {boolean} isAbort Determines if the exception case is caused by a transaction abort
 738    * @return {object}
 739    */
 740     createExceptionObject:function(tId, callbackArg, isAbort)
 741     {
 742                 var COMM_CODE = 0,
 743                         COMM_ERROR = 'communication failure',
 744                         ABORT_CODE = -1,
 745                         ABORT_ERROR = 'transaction aborted',
 746                         obj = {};
 747
 748                 obj.tId = tId;
 749                 if(isAbort){
 750                         obj.status = ABORT_CODE;
 751                         obj.statusText = ABORT_ERROR;
 752                 }
 753                 else{
 754                         obj.status = COMM_CODE;
 755                         obj.statusText = COMM_ERROR;
 756                 }
 757
 758                 if(callbackArg){
 759                         obj.argument = callbackArg;
 760                 }
 761
 762                 return obj;
 763     },
 764
 765   /**
 766    * @description Method that initializes the custom HTTP headers for the each transaction.
 767    * @method initHeader
 768    * @public
 769    * @static
 770    * @param {string} label The HTTP header label
 771    * @param {string} value The HTTP header value
 772    * @param {string} isDefault Determines if the specific header is a default header
 773    * automatically sent with each transaction.
 774    * @return {void}
 775    */
 776         initHeader:function(label, value, isDefault)
 777         {
 778                 var headerObj = (isDefault)?this._default_headers:this._http_headers;
 779
 780                 headerObj[label] = value;
 781                 if(isDefault){
 782                         this._has_default_headers = true;
 783                 }
 784                 else{
 785                         this._has_http_headers = true;
 786                 }
 787         },
 788
 789
 790   /**
 791    * @description Accessor that sets the HTTP headers for each transaction.
 792    * @method setHeader
 793    * @private
 794    * @static
 795    * @param {object} o The connection object for the transaction.
 796    * @return {void}
 797    */
 798         setHeader:function(o)
 799         {
 800                 var prop;
 801                 if(this._has_default_headers){
 802                         for(prop in this._default_headers){
 803                                 if(YAHOO.lang.hasOwnProperty(this._default_headers, prop)){
 804                                         o.conn.setRequestHeader(prop, this._default_headers[prop]);
 805                                 }
 806                         }
 807                 }
 808
 809                 if(this._has_http_headers){
 810                         for(prop in this._http_headers){
 811                                 if(YAHOO.lang.hasOwnProperty(this._http_headers, prop)){
 812                                         o.conn.setRequestHeader(prop, this._http_headers[prop]);
 813                                 }
 814                         }
 815
 816                         this._http_headers = {};
 817                         this._has_http_headers = false;
 818                 }
 819         },
 820
 821   /**
 822    * @description Resets the default HTTP headers object
 823    * @method resetDefaultHeaders
 824    * @public
 825    * @static
 826    * @return {void}
 827    */
 828         resetDefaultHeaders:function(){
 829                 this._default_headers = {};
 830                 this._has_default_headers = false;
 831         },
 832
 833   /**
 834    * @description Method to terminate a transaction, if it has not reached readyState 4.
 835    * @method abort
 836    * @public
 837    * @static
 838    * @param {object} o The connection object returned by asyncRequest.
 839    * @param {object} callback  User-defined callback object.
 840    * @param {string} isTimeout boolean to indicate if abort resulted from a callback timeout.
 841    * @return {boolean}
 842    */
 843         abort:function(o, callback, isTimeout)
 844         {
 845                 var abortStatus,
 846                         args = (callback && callback.argument)?callback.argument:null;
 847                         o = o || {};
 848
 849                 if(o.conn){
 850                         if(o.xhr){
 851                                 if(this.isCallInProgress(o)){
 852                                         // Issue abort request
 853                                         o.conn.abort();
 854
 855                                         window.clearInterval(this._poll[o.tId]);
 856                                         delete this._poll[o.tId];
 857
 858                                         if(isTimeout){
 859                                                 window.clearTimeout(this._timeOut[o.tId]);
 860                                                 delete this._timeOut[o.tId];
 861                                         }
 862
 863                                         abortStatus = true;
 864                                 }
 865                         }
 866                         else if(o.xdr){
 867                                 o.conn.abort(o.tId);
 868                                 abortStatus = true;
 869                         }
 870                 }
 871                 else if(o.upload){
 872                         var frameId = 'yuiIO' + o.tId;
 873                         var io = document.getElementById(frameId);
 874
 875                         if(io){
 876                                 // Remove all listeners on the iframe prior to
 877                                 // its destruction.
 878                                 YAHOO.util.Event.removeListener(io, "load");
 879                                 // Destroy the iframe facilitating the transaction.
 880                                 document.body.removeChild(io);
 881
 882                                 if(isTimeout){
 883                                         window.clearTimeout(this._timeOut[o.tId]);
 884                                         delete this._timeOut[o.tId];
 885                                 }
 886
 887                                 abortStatus = true;
 888                         }
 889                 }
 890                 else{
 891                         abortStatus = false;
 892                 }
 893
 894                 if(abortStatus === true){
 895                         // Fire global custom event -- abortEvent
 896                         this.abortEvent.fire(o, args);
 897
 898                         if(o.abortEvent){
 899                                 // Fire transaction custom event -- abortEvent
 900                                 o.abortEvent.fire(o, args);
 901                         }
 902
 903                         this.handleTransactionResponse(o, callback, true);
 904                 }
 905
 906                 return abortStatus;
 907         },
 908
 909   /**
 910    * @description Determines if the transaction is still being processed.
 911    * @method isCallInProgress
 912    * @public
 913    * @static
 914    * @param {object} o The connection object returned by asyncRequest
 915    * @return {boolean}
 916    */
 917         isCallInProgress:function(o)
 918         {
 919                 o = o || {};
 920                 // if the XHR object assigned to the transaction has not been dereferenced,
 921                 // then check its readyState status.  Otherwise, return false.
 922                 if(o.xhr && o.conn){
 923                         return o.conn.readyState !== 4 && o.conn.readyState !== 0;
 924                 }
 925                 else if(o.xdr && o.conn){
 926                         return o.conn.isCallInProgress(o.tId);
 927                 }
 928                 else if(o.upload === true){
 929                         return document.getElementById('yuiIO' + o.tId)?true:false;
 930                 }
 931                 else{
 932                         return false;
 933                 }
 934         },
 935
 936   /**
 937    * @description Dereference the XHR instance and the connection object after the transaction is completed.
 938    * @method releaseObject
 939    * @private
 940    * @static
 941    * @param {object} o The connection object
 942    * @return {void}
 943    */
 944         releaseObject:function(o)
 945         {
 946                 if(o && o.conn){
 947                         //dereference the XHR instance.
 948                         o.conn = null;
 949
 950
 951                         //dereference the connection object.
 952                         o = null;
 953                 }
 954         }
 955 };
 956
 957 YAHOO.register("connection_core", YAHOO.util.Connect, {version: "2.8.0r4", build: "2449"});