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wp-content/plugins/wp-optimize/js/queue.js

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+/**
+Adapted and extended from the work of Stephen Morley - http://code.stephenmorley.org/javascript/queues/
+
+Queue.js
+
+A function to represent a queue
+
+Created by Stephen Morley - http://code.stephenmorley.org/ - and released under
+the terms of the CC0 1.0 Universal legal code:
+
+http://creativecommons.org/publicdomain/zero/1.0/legalcode
+ */
+
+/**
+ * Creates a new queue. A queue is a first-in-first-out (FIFO) data structure -
+ * items are added to the end of the queue and removed from the front.
+ *
+ * @return {void}
+ */
+function Updraft_Queue() {
+
+	// Initialise the queue and offset.
+	var queue  = [];
+	var offset = 0;
+	var locked = false;
+
+	/**
+	* Returns the length of the queue.
+	*
+	* @returns {number} - the length of the queue
+	*/
+	this.get_length = function () {
+		return (queue.length - offset);
+	}
+
+	/**
+	* Query whether the queue is empty or not
+	*
+	* @returns {boolean} - returns true if the queue is empty, and false otherwise.
+	*/
+	this.is_empty = function () {
+		return (queue.length == 0);
+	}
+
+	/**
+	 * Enqueues the specified item. The parameter is:
+	 *
+	 * @param {*} item The item to enqueue
+	 *
+	 * @return {void}
+	 */
+	this.enqueue = function (item) {
+		queue.push(item);
+	}
+	
+	/**
+	 * Returns the queue lock status
+	 *
+	 * @returns {boolean} - whether the queue is locked or not
+	 */
+	this.is_locked = function () {
+		return locked;
+	}
+	
+	/**
+	 * Attempt to get the queue lock
+	 *
+	 * @returns {boolean} - whether the attempt succeeded or not
+	 */
+	this.get_lock = function () {
+		if (locked) { return false; }
+		this.lock();
+		return true;
+	}
+
+	/**
+	* Dequeues an item and returns it. If the queue is empty, the value
+	* 'undefined' is returned.
+	*
+	* @returns {*} - returns and removes the item at the front of the queue, or undefined if the queue is empty
+	*/
+	this.dequeue = function () {
+
+		// If the queue is empty, return immediately.
+		if (queue.length == 0) return undefined;
+
+		// Store the item at the front of the queue.
+		var item = queue[offset];
+
+		// Increment the offset and remove the free space if necessary.
+		if ((++offset * 2) >= queue.length) {
+			queue  = queue.slice(offset);
+			offset = 0;
+		}
+
+		// Return the dequeued item.
+		return item;
+	}
+
+	/**
+	 * Lock the queue
+	 *
+	 * @returns {void}
+	 */
+	this.lock = function () {
+		locked = true;
+	}
+	
+	/**
+	 * Unlock the queue
+	 *
+	 * @returns {void}
+	 */
+	this.unlock = function () {
+		locked = false;
+	}
+	
+	/**
+	* Returns the item at the front of the queue (without dequeuing it). If the
+	* queue is empty then undefined is returned.
+	*
+	* @returns {*} - returns the item at the front of the queue, or undefined if the queue is empty
+	*/
+	this.peek = function () {
+		return (queue.length > 0 ? queue[offset] : undefined);
+	}
+	
+	/**
+	 * Replaces the item at the front of the queue (if any)
+	 *
+	 * @param {*} item       The item to put at the front of the queue.
+	 *
+	 * @return {boolean}      Whether or not the item was successfully replaced.
+	 */
+	this.replace_front = function (item) {
+		if (queue.length < 1) { return false; }
+		queue[offset] = item;
+		return true;
+	}
+
+}
+