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<?php
/** @file splqueue.inc
* @ingroup SPL
* @brief class SplQueue
* @author Etienne Kneuss
* @date 2008
*
* SPL - Standard PHP Library
*/
/** @ingroup SPL
* @brief Implementation of a Queue through a DoublyLinkedList. As SplQueue
* extends SplDoublyLinkedList, unshift() and pop() are still available
* even though they don't make much sense for a queue. For convenience,
* two aliases are available:
* - enqueue() is an alias of push()
* - dequeue() is an alias of shift()
*
* @since PHP 5.3
*
* The SplQueue class provides the main functionalities of a
* queue implemented using a doubly linked list (DLL).
*/
class SplQueue extends SplDoublyLinkedList
{
protected $_it_mode = parent::IT_MODE_FIFO;
/** Changes the iteration mode. There are two orthogonal sets of modes that
* can be set:
*
* - The behavior of the iterator (either one or the other)
* - SplDoublyLnkedList::IT_MODE_DELETE (Elements are deleted by the iterator)
* - SplDoublyLnkedList::IT_MODE_KEEP (Elements are traversed by the iterator)
*
* The default mode is 0 : SplDoublyLnkedList::IT_MODE_LIFO | SplDoublyLnkedList::IT_MODE_KEEP
*
* @note The iteration's direction is not modifiable for queue instances
* @param $mode New mode of iteration
* @throw RuntimeException If the new mode affects the iteration's direction.
*/
public function setIteratorMode($mode)
{
if ($mode & parent::IT_MODE_LIFO === parent::IT_MODE_LIFO) {
throw new RuntimeException("Iterators' LIFO/FIFO modes for SplStack/SplQueue objects are frozen");
}
$this->_it_mode = $mode;
}
/** @return the first element of the queue.
* @note dequeue is an alias of push()
* @see splDoublyLinkedList::push()
*/
public function dequeue()
{
return parent::shift();
}
/** Pushes an element at the end of the queue.
* @param $data variable to add to the queue.
* @note enqueue is an alias of shift()
* @see splDoublyLinkedList::shift()
*/
public function enqueue($data)
{
return parent::push($data);
}
}
?>
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