<?php
/** @file spldoublylinkedlist.inc
* @ingroup SPL
* @brief class SplDoublyLinkedList
* @author Etienne Kneuss
* @date 2008 - 2009
*
* SPL - Standard PHP Library
*/
/** @ingroup SPL
* @brief Doubly Linked List
* @since PHP 5.3
*
* The SplDoublyLinkedList class provides the main functionalities of a
* doubly linked list (DLL).
* @note The following userland implementation of Iterator is a bit different
* from the internal one. Internally, iterators generated by nested
* foreachs are independent, while they share the same traverse pointer
* in userland.
*/
class SplDoublyLinkedList implements Iterator, ArrayAccess, Countable
{
protected $_llist = array();
protected $_it_mode = 0;
protected $_it_pos = 0;
/** Iterator mode
* @see setIteratorMode
*/
const IT_MODE_LIFO = 0x00000002;
/** Iterator mode
* @see setIteratorMode
*/
const IT_MODE_FIFO = 0x00000000;
/** Iterator mode
* @see setIteratorMode
*/
const IT_MODE_KEEP = 0x00000000;
/** Iterator mode
* @see setIteratorMode
*/
const IT_MODE_DELETE = 0x00000001;
/** @return the element popped from the end of the DLL.
* @throw RuntimeException If the datastructure is empty.
*/
public function pop()
{
if (count($this->_llist) == 0) {
throw new RuntimeException("Can't pop from an empty datastructure");
}
return array_pop($this->_llist);
}
/** @return the element shifted from the beginning of the DLL.
* @throw RuntimeException If the datastructure is empty.
*/
public function shift()
{
if (count($this->_llist) == 0) {
throw new RuntimeException("Can't shift from an empty datastructure");
}
return array_shift($this->_llist);
}
/** Pushes an element to the end of the DLL.
* @param $data variable to add to the DLL.
*/
public function push($data)
{
array_push($this->_llist, $data);
return true;
}
/** Adds an element to the beginning of the DLL.
* @param $data variable to add to the DLL.
*/
public function unshift($data)
{
array_unshift($this->_llist, $data);
return true;
}
/** @return the element at the beginning of the DLL.
*/
public function top()
{
return end($this->_llist);
}
/** @return the element at the end of the DLL.
*/
public function bottom()
{
return reset($this->_llist);
}
/** @return number elements in the DLL.
*/
public function count()
{
return count($this->_llist);
}
/** @return whether the DLL is empty.
*/
public function isEmpty()
{
return ($this->count() == 0);
}
/** Changes the iteration mode. There are two orthogonal sets of modes that
* can be set:
* - The direction of the iteration (either one or the other)
* - SplDoublyLnkedList::IT_MODE_LIFO (Stack style)
* - SplDoublyLnkedList::IT_MODE_FIFO (Queue style)
*
* - 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_FIFO | SplDoublyLnkedList::IT_MODE_KEEP
*
* @param $mode new mode of iteration
*/
public function setIteratorMode($mode)
{
$this->_it_mode = $mode;
}
/** @return the current iteration mode
* @see setIteratorMode
*/
public function getIteratorMode()
{
return $this->_it_mode;
}
/** Rewind to top iterator as set in constructor
*/
public function rewind()
{
if ($this->_it_mode & self::IT_MODE_LIFO) {
$this->_it_pos = count($this->_llist)-1;
} else {
$this->_it_pos = 0;
}
}
/** @return whether iterator is valid
*/
public function valid()
{
return array_key_exists($this->_it_pos, $this->_llist);
}
/** @return current key
*/
public function key()
{
return $this->_it_pos;
}
/** @return current object
*/
public function current()
{
return $this->_llist[$this->_it_pos];
}
/** Forward to next element
*/
public function next()
{
if ($this->_it_mode & self::IT_MODE_LIFO) {
if ($this->_it_mode & self::IT_MODE_DELETE) {
$this->pop();
}
$this->_it_pos--;
} else {
if ($this->_it_mode & self::IT_MODE_DELETE) {
$this->shift();
} else {
$this->_it_pos++;
}
}
}
/** @return whether a certain offset exists in the DLL
*
* @param $offset The offset
* @throw OutOfRangeException If the offset is either invalid or out of
* range.
*/
public function offsetExists($offset)
{
if (!is_numeric($offset)) {
throw new OutOfRangeException("Offset invalid or out of range");
} else {
return array_key_exists($offset, $this->_llist);
}
}
/** @return the data at a certain offset in the DLL
*
* @param $offset The offset
* @throw OutOfRangeException If the offset is either invalid or out of
* range.
*/
public function offsetGet($offset)
{
if ($this->_it_mode & self::IT_MODE_LIFO) {
$realOffset = count($this->_llist)-$offset;
} else {
$realOffset = $offset;
}
if (!is_numeric($offset) || !array_key_exists($realOffset, $this->_llist)) {
throw new OutOfRangeException("Offset invalid or out of range");
} else {
return $this->_llist[$realOffset];
}
}
/** Defines the data at a certain offset in the DLL
*
* @param $offset The offset
* @param $value New value
* @throw OutOfRangeException If the offset is either invalid or out of
* range.
*/
public function offsetSet($offset, $value)
{
if ($offset === null) {
return $this->push($value);
}
if ($this->_it_mode & self::IT_MODE_LIFO) {
$realOffset = count($this->_llist)-$offset;
} else {
$realOffset = $offset;
}
if (!is_numeric($offset) || !array_key_exists($realOffset, $this->_llist)) {
throw new OutOfRangeException("Offset invalid or out of range");
} else {
$this->_llist[$realOffset] = $value;
}
}
/** Unsets the element at a certain offset in the DLL
*
* @param $offset The offset
* @throw OutOfRangeException If the offset is either invalid or out of
* range.
*/
public function offsetUnset($offset)
{
if ($this->_it_mode & self::IT_MODE_LIFO) {
$realOffset = count($this->_llist)-$offset;
} else {
$realOffset = $offset;
}
if (!is_numeric($offset) || !array_key_exists($realOffset, $this->_llist)) {
throw new OutOfRangeException("Offset invalid or out of range");
} else {
array_splice($this->_llist, $realOffset, 1);
}
}
}
?>
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