/*
* Copyright (c) 2002-2007 Sun Microsystems, Inc. All rights reserved.
*
* The Sun Project JXTA(TM) Software License
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* 3. The end-user documentation included with the redistribution, if any, must
* include the following acknowledgment: "This product includes software
* developed by Sun Microsystems, Inc. for JXTA(TM) technology."
* Alternately, this acknowledgment may appear in the software itself, if
* and wherever such third-party acknowledgments normally appear.
*
* 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA" must
* not be used to endorse or promote products derived from this software
* without prior written permission. For written permission, please contact
* Project JXTA at http://www.jxta.org.
*
* 5. Products derived from this software may not be called "JXTA", nor may
* "JXTA" appear in their name, without prior written permission of Sun.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL SUN
* MICROSYSTEMS OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
* OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* JXTA is a registered trademark of Sun Microsystems, Inc. in the United
* States and other countries.
*
* Please see the license information page at :
* <http://www.jxta.org/project/www/license.html> for instructions on use of
* the license in source files.
*
* ====================================================================
*
* This software consists of voluntary contributions made by many individuals
* on behalf of Project JXTA. For more information on Project JXTA, please see
* http://www.jxta.org.
*
* This license is based on the BSD license adopted by the Apache Foundation.
*/
package net.jxta.impl.util;
/**
* A dlinkable base class.
* It is far less general than java's LinkedList but permits much better
* removal performance from the middle of the list because a contained
* element and the corresponding chaining object are one and the same.
*
* The major inconvenient of this class is that it is...a class, not an
* interface. Making it an interface does not make sense since one would have
* to re-implement it entirely. There is almost no value added in a List class
* in addition to a Link class. A list of these Dlink is just a stand-alone
* Dlink with just a couple of additional convenience methods.
*/
public class Dlink {
/**
* Previous element in list.
*/
private Dlink prev;
/**
* Next element in list.
*/
private Dlink next;
private void setNext(Dlink n) {
next = n;
}
private void setPrev(Dlink p) {
prev = p;
}
public Dlink next() {
return next;
}
public Dlink prev() {
return prev;
}
public void unlink() {
next.setPrev(prev);
prev.setNext(next);
next = prev = this;
}
public boolean isLinked() {
return next != this;
}
public void linkNewNext(Dlink ne) {
ne.unlink();
ne.setPrev(this);
ne.setNext(next);
next.setPrev(ne);
next = ne;
}
public void linkNewPrev(Dlink ne) {
ne.unlink();
ne.setNext(this);
ne.setPrev(prev);
prev.setNext(ne);
prev = ne;
}
public Dlink() {
next = prev = this;
}
}