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# Q3PtrQueue Class Reference

The Q3PtrQueue class is a template class that provides a queue. More...

     #include <Q3PtrQueue>

This class is part of the Qt 3 support library. It is provided to keep old source code working. We strongly advise against using it in new code. See Porting to Qt 4 for more information.

Inherits: Q3PtrCollection.

- List of all members, including inherited members

## Public Functions

| Q3PtrQueue ()
| Q3PtrQueue ( const Q3PtrQueue<type> & queue )
| ~Q3PtrQueue ()
bool | autoDelete () const
type * | current () const
type * | dequeue ()
void | enqueue ( const type * d )
type * | head () const
bool | isEmpty () const
bool | remove ()
void | setAutoDelete ( bool enable )
| operator type * () const
Q3PtrQueue<type> & | operator= ( const Q3PtrQueue<type> & queue )

## Reimplemented Public Functions

virtual void | clear ()
virtual uint | count () const

- 4 public functions inherited from Q3PtrCollection

## Reimplemented Protected Functions

virtual QDataStream & | read ( QDataStream & s, Q3PtrCollection::Item & item )
virtual QDataStream & | write ( QDataStream & s, Q3PtrCollection::Item item ) const

- 2 protected functions inherited from Q3PtrCollection

## Detailed Description

The Q3PtrQueue class is a template class that provides a queue.

Q3ValueVector can be used as an STL-compatible alternative to this class.

A template instance Q3PtrQueue<X> is a queue that operates on pointers to X (X*).

A queue is a first in, first out structure. Items are added to the tail of the queue with enqueue() and retrieved from the head with dequeue(). You can peek at the head item without dequeing it using head().

You can control the queue's deletion policy with setAutoDelete().

For compatibility with the Q3PtrCollection classes, current() and remove() are provided; both operate on the head().

See also Q3PtrList and Q3PtrStack.

## Member Function Documentation

### Q3PtrQueue::Q3PtrQueue ()

Creates an empty queue with autoDelete() set to FALSE.

### Q3PtrQueue::Q3PtrQueue ( const Q3PtrQueue<type> & queue )

Creates a queue from queue.

Only the pointers are copied; the items are not. The autoDelete() flag is set to FALSE.

### Q3PtrQueue::~Q3PtrQueue ()

Destroys the queue. Items in the queue are deleted if autoDelete() is TRUE.

### bool Q3PtrQueue::autoDelete () const

Returns the setting of the auto-delete option. The default is FALSE.

See also setAutoDelete().

### void Q3PtrQueue::clear ()`[virtual]`

Reimplemented from Q3PtrCollection::clear().

Removes all items from the queue, and deletes them if autoDelete() is TRUE.

See also remove().

### uint Q3PtrQueue::count () const`[virtual]`

Reimplemented from Q3PtrCollection::count().

Returns the number of items in the queue.

See also isEmpty().

### type * Q3PtrQueue::current () const

Returns a pointer to the head item in the queue. The queue is not changed. Returns 0 if the queue is empty.

See also dequeue() and isEmpty().

### type * Q3PtrQueue::dequeue ()

Takes the head item from the queue and returns a pointer to it. Returns 0 if the queue is empty.

See also enqueue() and count().

### void Q3PtrQueue::enqueue ( const type * d )

Adds item d to the tail of the queue.

See also count() and dequeue().

### type * Q3PtrQueue::head () const

Returns a pointer to the head item in the queue. The queue is not changed. Returns 0 if the queue is empty.

See also dequeue() and isEmpty().

### bool Q3PtrQueue::isEmpty () const

Returns TRUE if the queue is empty; otherwise returns FALSE.

See also count(), dequeue(), and head().

### QDataStream & Q3PtrQueue::read ( QDataStream & s, Q3PtrCollection::Item & item )`[virtual protected]`

Reads a queue item, item, from the stream s and returns a reference to the stream.

The default implementation sets item to 0.

See also write().

### bool Q3PtrQueue::remove ()

Removes the head item from the queue, and returns TRUE if there was an item, i.e. the queue wasn't empty; otherwise returns FALSE.

The item is deleted if autoDelete() is TRUE.

See also head(), isEmpty(), and dequeue().

### void Q3PtrQueue::setAutoDelete ( bool enable )

Sets the queue to auto-delete its contents if enable is TRUE and not to delete them if enable is FALSE.

If auto-deleting is turned on, all the items in a queue are deleted when the queue itself is deleted. This can be quite convenient if the queue has the only pointer to the items.

The default setting is FALSE, for safety. If you turn it on, be careful about copying the queue: you might find yourself with two queues deleting the same items.

See also autoDelete().

### QDataStream & Q3PtrQueue::write ( QDataStream & s, Q3PtrCollection::Item item ) const`[virtual protected]`

Writes a queue item, item, to the stream s and returns a reference to the stream.

The default implementation does nothing.

See also read().

### Q3PtrQueue::operator type * () const

Returns a pointer to the head item in the queue. The queue is not changed. Returns 0 if the queue is empty.

See also dequeue() and isEmpty().

### Q3PtrQueue<type> & Q3PtrQueue::operator= ( const Q3PtrQueue<type> & queue )

Assigns queue to this queue and returns a reference to this queue.

This queue is first cleared and then each item in queue is enqueued to this queue. Only the pointers are copied.

Warning: The autoDelete() flag is not modified. If it is TRUE for both queue and this queue, deleting the two lists will cause double-deletion of the items.