jQuery.error( callbackName + " was not called" );
}
return responseContainer[ 0 ];
};

// force json dataType
s.dataTypes[ 0 ] = "json";

// Install callback
overwritten = window[ callbackName ];
window[ callbackName ] = function() {
responseContainer = arguments;
};

// Clean-up function (fires after converters)
jqXHR.always(function() {
// Restore preexisting value
window[ callbackName ] = overwritten;

// Save back as free
if ( s[ callbackName ] ) {
// make sure that re-using the options doesn't screw things around
s.jsonpCallback = originalSettings.jsonpCallback;

// save the callback name for future use
oldCallbacks.push( callbackName );
}

// Call if it was a function and we have a response
if ( responseContainer && jQuery.isFunction( overwritten ) ) {
overwritten( responseContainer[ 0 ] );
}

responseContainer = overwritten = undefined;
});

// Delegate to script
return "script";
}
});
var xhrCallbacks, xhrSupported,
xhrId = 0,
// #5280: Internet Explorer will keep connections alive if we don't abort on unload
xhrOnUnloadAbort = window.ActiveXObject && function() {
// Abort all pending requests
var key;
for ( key in xhrCallbacks ) {
xhrCallbacks[ key ]( undefined, true );
}
};

// Functions to create xhrs
function createStandardXHR() {
try {
return new window.XMLHttpRequest();
} catch( e ) {}
}

function createActiveXHR() {
try {
return new window.ActiveXObject("Microsoft.XMLHTTP");
} catch( e ) {}
}

// Create the request object
// (This is still attached to ajaxSettings for backward compatibility)
jQuery.ajaxSettings.xhr = window.ActiveXObject ?
/* Microsoft failed to properly
* implement the XMLHttpRequest in IE7 (can't request local files),
* so we use the ActiveXObject when it is available
* Additionally XMLHttpRequest can be disabled in IE7/IE8 so
* we need a fallback.
*/
function() {
return !this.isLocal && createStandardXHR() || createActiveXHR();
} :
// For all other browsers, use the standard XMLHttpRequest object
createStandardXHR;

// Determine support properties
xhrSupported = jQuery.ajaxSettings.xhr();
jQuery.support.cors = !!xhrSupported && ( "withCredentials" in xhrSupported );
xhrSupported = jQuery.support.ajax = !!xhrSupported;

// Create transport if the browser can provide an xhr
if ( xhrSupported ) {

jQuery.ajaxTransport(function( s ) {
// Cross domain only allowed if supported through XMLHttpRequest
if ( !s.crossDomain || jQuery.support.cors ) {

var callback;

return {
send: function( headers, complete ) {

// Get a new xhr
var handle, i,
xhr = s.xhr();

// Open the socket
// Passing null username, generates a login popup on Opera (#2865)
if ( s.username ) {
xhr.open( s.type, s.url, s.async, s.username, s.password );
} else {
xhr.open( s.type, s.url, s.async );
}

// Apply custom fields if provided
if ( s.xhrFields ) {
for ( i in s.xhrFields ) {
xhr[ i ] = s.xhrFields[ i ];
}
}

// Override mime type if needed
if ( s.mimeType && xhr.overrideMimeType ) {
xhr.overrideMimeType( s.mimeType );
}

// X-Requested-With header
// For cross-domain requests, seeing as conditions for a preflight are
// akin to a jigsaw puzzle, we simply never set it to be sure.
// (it can always be set on a per-request basis or even using ajaxSetup)
// For same-domain requests, won't change header if already provided.
if ( !s.crossDomain && !headers["X-Requested-With"] ) {
headers["X-Requested-With"] = "XMLHttpRequest";
}

// Need an extra try/catch for cross domain requests in Firefox 3
try {
for ( i in headers ) {
xhr.setRequestHeader( i, headers[ i ] );
}
} catch( err ) {}

// Do send the request
// This may raise an exception which is actually
// handled in jQuery.ajax (so no try/catch here)
xhr.send( ( s.hasContent && s.data ) || null );

// Listener
callback = function( _, isAbort ) {
var status, responseHeaders, statusText, responses;

// Firefox throws exceptions when accessing properties
// of an xhr when a network error occurred
// http://helpful.knobs-dials.com/index.php/Component_returned_failure_code:_0x80040111_(NS_ERROR_NOT_AVAILABLE)
try {

// Was never called and is aborted or complete
if ( callback && ( isAbort || xhr.readyState === 4 ) ) {

// Only called once
callback = undefined;

// Do not keep as active anymore
if ( handle ) {
xhr.onreadystatechange = jQuery.noop;
if ( xhrOnUnloadAbort ) {
delete xhrCallbacks[ handle ];
}
}

// If it's an abort
if ( isAbort ) {
// Abort it manually if needed
if ( xhr.readyState !== 4 ) {
xhr.abort();
}
} else {
responses = {};
status = xhr.status;
responseHeaders = xhr.getAllResponseHeaders();

// When requesting binary data, IE6-9 will throw an exception
// on any attempt to access responseText (#11426)
if ( typeof xhr.responseText === "string" ) {
responses.text = xhr.responseText;
}

// Firefox throws an exception when accessing
// statusText for faulty cross-domain requests
try {
statusText = xhr.statusText;
} catch( e ) {
// We normalize with Webkit giving an empty statusText
statusText = "";
}

// Filter status for non standard behaviors

// If the request is local and we have data: assume a success
// (success with no data won't get notified, that's the best we
// can do given current implementations)
if ( !status && s.isLocal && !s.crossDomain ) {
status = responses.text ? 200 : 404;
// IE - #1450: sometimes returns 1223 when it should be 204
} else if ( status === 1223 ) {
status = 204;
}
}
}