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/* queue.vala
*
* Copyright (C) 2009 Didier Villevalois
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* Author:
* Didier 'Ptitjes Villevalois <ptitjes@free.fr>
*/
/**
* A collection designed for holding elements prior to processing.
*
* Although all Queue implementations do not limit the amount of elements they
* can contain, this interface supports for capacity-bounded queues. When
* capacity is not bound, then the {@link capacity} and
* {@link remaining_capacity} both return {@link UNBOUNDED_CAPACITY}.
*
* This interface defines methods that will never fail whatever the state of
* the queue is. For capacity-bounded queues, those methods will either return
* ``false`` or ``null`` to specify that the insert or retrieval did not occur
* because the queue was full or empty.
*
* Queue implementations are not limited to First-In-First-Out behavior and can
* propose different ordering of their elements. Each Queue implementation have
* to specify how it orders its elements.
*
* Queue implementations do not allow insertion of ``null`` elements, although
* some implementations, such as {@link LinkedList}, do not prohibit insertion
* of ``null``. Even in the implementations that permit it, ``null`` should not be
* inserted into a Queue, as ``null`` is also used as a special return value by
* the poll method to indicate that the queue contains no elements.
*/
[GenericAccessors]
public interface Gee.Queue<G> : Collection<G> {
/**
* The unbounded capacity value.
*/
public const int UNBOUNDED_CAPACITY = -1;
/**
* The capacity of this queue (or ``UNBOUNDED_CAPACITY`` if capacity is not bound).
*/
public abstract int capacity { get; }
/**
* The remaining capacity of this queue (or ``UNBOUNDED_CAPACITY`` if capacity is not
* bound).
*/
public abstract int remaining_capacity { get; }
/**
* Specifies whether this queue is full.
*/
public abstract bool is_full { get; }
/**
* Offers the specified element to this queue.
*
* @param element the element to offer to the queue
*
* @return ``true`` if the element was added to the queue
*/
public virtual bool offer (G element) {
return add (element);
}
/**
* Peeks (retrieves, but not remove) an element from this queue.
*
* @return the element peeked from the queue (or ``null`` if none was
* available)
*/
public abstract G? peek ();
/**
* Polls (retrieves and remove) an element from this queue.
*
* @return the element polled from the queue (or ``null`` if none was
* available)
*/
public abstract G? poll ();
/**
* Drains the specified amount of elements from this queue in the specified
* recipient collection.
*
* @param recipient the recipient collection to drain the elements to
* @param amount the amount of elements to drain
*
* @return the amount of elements that were actually drained
*/
public virtual int drain (Collection<G> recipient, int amount = -1) {
G? item = null;
int drained = 0;
while((amount == -1 || --amount >= 0) && (item = poll ()) != null) {
recipient.add (item);
drained++;
}
return drained;
}
}
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