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<?php
/**
* TQueue, TQueueIterator classes
*
* @author Qiang Xue <qiang.xue@gmail.com>
* @link http://www.pradosoft.com/
* @copyright Copyright © 2005-2014 PradoSoft
* @license http://www.pradosoft.com/license/
* @version $Id$
* @package System.Collections
*/
/**
* TQueue class
*
* TQueue implements a queue.
*
* The typical queue operations are implemented, which include
* {@link enqueue()}, {@link dequeue()} and {@link peek()}. In addition,
* {@link contains()} can be used to check if an item is contained
* in the queue. To obtain the number of the items in the queue,
* check the {@link getCount Count} property.
*
* Items in the queue may be traversed using foreach as follows,
* <code>
* foreach($queue as $item) ...
* </code>
*
* @author Qiang Xue <qiang.xue@gmail.com>
* @author Knut Urdalen <knut.urdalen@gmail.com>
* @version $Id$
* @package System.Collections
* @since 3.1
*/
class TQueue extends TComponent implements IteratorAggregate,Countable
{
/**
* internal data storage
* @var array
*/
private $_d=array();
/**
* number of items
* @var integer
*/
private $_c=0;
/**
* Constructor.
* Initializes the queue with an array or an iterable object.
* @param array|Iterator the intial data. Default is null, meaning no initialization.
* @throws TInvalidDataTypeException If data is not null and neither an array nor an iterator.
*/
public function __construct($data=null)
{
if($data!==null)
$this->copyFrom($data);
}
/**
* @return array the list of items in queue
*/
public function toArray()
{
return $this->_d;
}
/**
* Copies iterable data into the queue.
* Note, existing data in the list will be cleared first.
* @param mixed the data to be copied from, must be an array or object implementing Traversable
* @throws TInvalidDataTypeException If data is neither an array nor a Traversable.
*/
public function copyFrom($data)
{
if(is_array($data) || ($data instanceof Traversable))
{
$this->clear();
foreach($data as $item)
{
$this->_d[]=$item;
++$this->_c;
}
}
else if($data!==null)
throw new TInvalidDataTypeException('queue_data_not_iterable');
}
/**
* Removes all items in the queue.
*/
public function clear()
{
$this->_c=0;
$this->_d=array();
}
/**
* @param mixed the item
* @return boolean whether the queue contains the item
*/
public function contains($item)
{
return array_search($item,$this->_d,true)!==false;
}
/**
* Returns the first item at the front of the queue.
* Unlike {@link dequeue()}, this method does not remove the item from the queue.
* @return mixed item at the top of the queue
* @throws TInvalidOperationException if the queue is empty
*/
public function peek()
{
if($this->_c===0)
throw new TInvalidOperationException('queue_empty');
else
return $this->_d[0];
}
/**
* Removes and returns the object at the beginning of the queue.
* @return mixed the item at the beginning of the queue
* @throws TInvalidOperationException if the queue is empty
*/
public function dequeue()
{
if($this->_c===0)
throw new TInvalidOperationException('queue_empty');
else
{
--$this->_c;
return array_shift($this->_d);
}
}
/**
* Adds an object to the end of the queue.
* @param mixed the item to be appended into the queue
*/
public function enqueue($item)
{
++$this->_c;
$this->_d[] = $item;
}
/**
* Returns an iterator for traversing the items in the queue.
* This method is required by the interface IteratorAggregate.
* @return Iterator an iterator for traversing the items in the queue.
*/
public function getIterator()
{
return new ArrayIterator( $this->_d );
}
/**
* @return integer the number of items in the queue
*/
public function getCount()
{
return $this->_c;
}
/**
* Returns the number of items in the queue.
* This method is required by Countable interface.
* @return integer number of items in the queue.
*/
public function count()
{
return $this->getCount();
}
}
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