<?php
/**
* <p>Title: Double linked list</p>
* <p>Description: Implementation of a double linked list in PHP</p>
* @author Oddleif Halvorsen | leif-h@online.no
* @version 1.2
*/
class Iterator{
var $currentNode;
var $previousNode;
var $nextNode;
var $list; //should not be nessesary to use. Ineffecive on large lists.
/**
* Constructs an iterator.
* @param &$head The object/value of the node
* @param &$list The LinkedList, used for easy deletes of nodes.
*/
function Iterator(&$head, &$list){
$this->currentNode = &$head;
$this->previousNode = &$this->currentNode->getPrevious();
$this->nextNode = &$this->currentNode->getNext();
$this->list = &$list;
}
/**
* Checks if more nodes exist
* @return TRUE == hasNext || FALSE == no next node.
*/
function hasNext(){
//current node must exist and be different from NULL OR next node exists.
return (($this->currentNode != NULL && $this->currentNode->getNext() != NULL) || $this->nextNode != NULL ? TRUE : FALSE);
}
/**
* Get the the next node.
* Checks if there is a next node, if no next node it
* returns false.
* @return The object at current node
*/
function getNext(){
if($this->hasNext()){
//checks if current node is deleted.
if($this->currentNode != NULL)
$this->currentNode = &$this->currentNode->getNext();
else
$this->currentNode = &$this->nextNode;
$this->previousNode = &$this->currentNode->getPrevious();
$this->nextNode = &$this->currentNode->getNext();
return $this->currentNode->getNodeValue();
}
return FALSE;
}
/**
* Removes the current node
* Uses the list removeObjectAtIndex it it is the head
* or tail that is to be removed.
*/
function remove(){
if($this->currentNode->getPrevious() == NULL)
$this->list->removeObjectAtIndex(0);
else
if($this->currentNode->getNext() == NULL)
$this->list->removeObjectAtIndex(($this->list->size()-1));
else{
//updates the references for the before and after the current node.
$this->previousNode->setNext(&$this->nextNode);
$this->nextNode->setPrevious(&$this->previousNode);
$this->list->decSize();
}
$this->currentNode->setNext(NULL);
$this->currentNode->setPrevious(NULL);
$this->currentNode = NULL;
}
}
?>
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