xref: /PHP-7.1/ext/spl/internal/splqueue.inc (revision 7f6387b5)
1<?php
2
3/** @file splqueue.inc
4 * @ingroup SPL
5 * @brief class SplQueue
6 * @author  Etienne Kneuss
7 * @date    2008 - 2009
8 *
9 * SPL - Standard PHP Library
10 */
11
12/** @ingroup SPL
13 * @brief Implementation of a Queue through a DoublyLinkedList. As SplQueue
14 *        extends SplDoublyLinkedList, unshift() and pop() are still available
15 *        even though they don't make much sense for a queue. For convenience,
16 *        two aliases are available:
17 *         - enqueue() is an alias of push()
18 *         - dequeue() is an alias of shift()
19 *
20 * @since PHP 5.3
21 *
22 * The SplQueue class provides the main functionalities of a
23 * queue implemented using a doubly linked list (DLL).
24 */
25class SplQueue extends SplDoublyLinkedList
26{
27	protected $_it_mode = parent::IT_MODE_FIFO;
28
29	/** Changes the iteration mode. There are two orthogonal sets of modes that
30	 * can be set:
31	 *
32	 * - The behavior of the iterator (either one or the other)
33	 *  - SplDoublyLnkedList::IT_MODE_DELETE (Elements are deleted by the iterator)
34	 *  - SplDoublyLnkedList::IT_MODE_KEEP   (Elements are traversed by the iterator)
35	 *
36	 * The default mode is 0 : SplDoublyLnkedList::IT_MODE_LIFO | SplDoublyLnkedList::IT_MODE_KEEP
37	 *
38	 * @note The iteration's direction is not modifiable for queue instances
39	 * @param $mode              New mode of iteration
40	 * @throw RuntimeException   If the new mode affects the iteration's direction.
41	 */
42	public function setIteratorMode($mode)
43	{
44		if ($mode & parent::IT_MODE_LIFO === parent::IT_MODE_LIFO) {
45			throw new RuntimeException("Iterators' LIFO/FIFO modes for SplStack/SplQueue objects are frozen");
46		}
47
48		$this->_it_mode = $mode;
49	}
50
51	/** @return the first element of the queue.
52	 * @note dequeue is an alias of push()
53	 * @see splDoublyLinkedList::push()
54	 */
55	public function dequeue()
56	{
57		return parent::shift();
58	}
59
60	/** Pushes an element at the end of the queue.
61	 * @param $data variable to add to the queue.
62	 * @note enqueue is an alias of shift()
63	 * @see splDoublyLinkedList::shift()
64	 */
65	public function enqueue($data)
66	{
67		return parent::push($data);
68	}
69}
70
71?>
72