The source code

    /*
    	Queue Plug-in

    	Features:
    		*Adds a cancelQueue() method for cancelling the entire queue.
    		*All queued files are uploaded when startUpload() is called.
    		*If false is returned from uploadComplete then the queue upload is stopped.
    		 If false is not returned (strict comparison) then the queue upload is continued.
    		*Adds a QueueComplete event that is fired when all the queued files have finished uploading.
    		 Set the event handler with the queue_complete_handler setting.

    	*/

    var SWFUpload;
    if (typeof(SWFUpload) === "function") {
    	SWFUpload.queue = {};

    	SWFUpload.prototype.initSettings = (function (oldInitSettings) {
    		return function () {
    			if (typeof(oldInitSettings) === "function") {
    				oldInitSettings.call(this);
    			}

    			this.queueSettings = {};

    			this.queueSettings.queue_cancelled_flag = false;
    			this.queueSettings.queue_upload_count = 0;

    			this.queueSettings.user_upload_complete_handler = this.settings.upload_complete_handler;
    			this.queueSettings.user_upload_start_handler = this.settings.upload_start_handler;
    			this.settings.upload_complete_handler = SWFUpload.queue.uploadCompleteHandler;
    			this.settings.upload_start_handler = SWFUpload.queue.uploadStartHandler;

    			this.settings.queue_complete_handler = this.settings.queue_complete_handler || null;
    		};
    	})(SWFUpload.prototype.initSettings);

    	SWFUpload.prototype.startUpload = function (fileID) {
    		this.queueSettings.queue_cancelled_flag = false;
    		this.callFlash("StartUpload", [fileID]);
    	};

    	SWFUpload.prototype.cancelQueue = function () {
    		this.queueSettings.queue_cancelled_flag = true;
    		this.stopUpload();

    		var stats = this.getStats();
    		while (stats.files_queued > 0) {
    			this.cancelUpload();
    			stats = this.getStats();
    		}
    	};

    	SWFUpload.queue.uploadStartHandler = function (file) {
    		var returnValue;
    		if (typeof(this.queueSettings.user_upload_start_handler) === "function") {
    			returnValue = this.queueSettings.user_upload_start_handler.call(this, file);
    		}

    		// To prevent upload a real "FALSE" value must be returned, otherwise default to a real "TRUE" value.
    		returnValue = (returnValue === false) ? false : true;

    		this.queueSettings.queue_cancelled_flag = !returnValue;

    		return returnValue;
    	};

    	SWFUpload.queue.uploadCompleteHandler = function (file) {
    		var user_upload_complete_handler = this.queueSettings.user_upload_complete_handler;
    		var continueUpload;

    		if (file.filestatus === SWFUpload.FILE_STATUS.COMPLETE) {
    			this.queueSettings.queue_upload_count++;
    		}

    		if (typeof(user_upload_complete_handler) === "function") {
    			continueUpload = (user_upload_complete_handler.call(this, file) === false) ? false : true;
    		} else if (file.filestatus === SWFUpload.FILE_STATUS.QUEUED) {
    			// If the file was stopped and re-queued don't restart the upload
    			continueUpload = false;
    		} else {
    			continueUpload = true;
    		}

    		if (continueUpload) {
    			var stats = this.getStats();
    			if (stats.files_queued > 0 && this.queueSettings.queue_cancelled_flag === false) {
    				this.startUpload();
    			} else if (this.queueSettings.queue_cancelled_flag === false) {
    				this.queueEvent("queue_complete_handler", [this.queueSettings.queue_upload_count]);
    				this.queueSettings.queue_upload_count = 0;
    			} else {
    				this.queueSettings.queue_cancelled_flag = false;
    				this.queueSettings.queue_upload_count = 0;
    			}
    		}
    	};
    }