/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.activemq.store.kahadb.disk.util;
/**
* Provides a base class for you to extend when you want object to maintain a
* doubly linked list to other objects without using a collection class.
*
* @author chirino
*/
public class LinkedNode<T extends LinkedNode<T>> {
protected LinkedNodeList<T> list;
protected T next;
protected T prev;
public LinkedNode() {
}
@SuppressWarnings("unchecked")
private T getThis() {
return (T) this;
}
public T getHeadNode() {
return list.head;
}
public T getTailNode() {
return list.head.prev;
}
public T getNext() {
return isTailNode() ? null : next;
}
public T getPrevious() {
return isHeadNode() ? null : prev;
}
public T getNextCircular() {
return next;
}
public T getPreviousCircular() {
return prev;
}
public boolean isHeadNode() {
return list.head == this;
}
public boolean isTailNode() {
return list.head.prev == this;
}
/**
* @param node
* the node to link after this node.
* @return this
*/
public void linkAfter(T node) {
if (node == this) {
throw new IllegalArgumentException("You cannot link to yourself");
}
if (node.list != null) {
throw new IllegalArgumentException("You only insert nodes that are not in a list");
}
if (list == null) {
throw new IllegalArgumentException("This node is not yet in a list");
}
node.list = list;
// given we linked this<->next and are inserting node in between
node.prev = getThis(); // link this<-node
node.next = next; // link node->next
next.prev = node; // link node<-next
next = node; // this->node
list.size++;
}
/**
* @param rightList
* the node to link after this node.
* @return this
*/
public void linkAfter(LinkedNodeList<T> rightList) {
if (rightList == list) {
throw new IllegalArgumentException("You cannot link to yourself");
}
if (list == null) {
throw new IllegalArgumentException("This node is not yet in a list");
}
T rightHead = rightList.head;
T rightTail = rightList.head.prev;
list.reparent(rightList);
// given we linked this<->next and are inserting list in between
rightHead.prev = getThis(); // link this<-list
rightTail.next = next; // link list->next
next.prev = rightTail; // link list<-next
next = rightHead; // this->list
}
/**
* @param node
* the node to link after this node.
* @return
* @return this
*/
public void linkBefore(T node) {
if (node == this) {
throw new IllegalArgumentException("You cannot link to yourself");
}
if (node.list != null) {
throw new IllegalArgumentException("You only insert nodes that are not in a list");
}
if (list == null) {
throw new IllegalArgumentException("This node is not yet in a list");
}
node.list = list;
// given we linked prev<->this and are inserting node in between
node.next = getThis(); // node->this
node.prev = prev; // prev<-node
prev.next = node; // prev->node
prev = node; // node<-this
if (this == list.head) {
list.head = node;
}
list.size++;
}
/**
* @param leftList
* the node to link after this node.
* @return
* @return this
*/
public void linkBefore(LinkedNodeList<T> leftList) {
if (leftList == list) {
throw new IllegalArgumentException("You cannot link to yourself");
}
if (list == null) {
throw new IllegalArgumentException("This node is not yet in a list");
}
T leftHead = leftList.head;
T leftTail = leftList.head.prev;
list.reparent(leftList);
// given we linked prev<->this and are inserting list in between
leftTail.next = getThis(); // list->this
leftHead.prev = prev; // prev<-list
prev.next = leftHead; // prev->list
prev = leftTail; // list<-this
if (isHeadNode()) {
list.head = leftHead;
}
}
public void linkToTail(LinkedNodeList<T> target) {
if (list != null) {
throw new IllegalArgumentException("This node is already linked to a node");
}
if (target.head == null) {
next = prev = target.head = getThis();
list = target;
list.size++;
} else {
target.head.prev.linkAfter(getThis());
}
}
public void linkToHead(LinkedNodeList<T> target) {
if (list != null) {
throw new IllegalArgumentException("This node is already linked to a list");
}
if (target.head == null) {
next = prev = target.head = getThis();
list = target;
list.size++;
} else {
target.head.linkBefore(getThis());
}
}
/**
* Removes this node out of the linked list it is chained in.
*/
public boolean unlink() {
// If we are allready unlinked...
if (list == null) {
return false;
}
if (getThis() == prev) {
// We are the only item in the list
list.head = null;
} else {
// given we linked prev<->this<->next
next.prev = prev; // prev<-next
prev.next = next; // prev->next
if (isHeadNode()) {
list.head = next;
}
}
list.size--;
list = null;
return true;
}
/**
* Splits the list into 2 lists. This node becomes the tail of this list.
* Then 2nd list is returned.
*
* @return An empty list if this is a tail node.
*/
public LinkedNodeList<T> splitAfter() {
if (isTailNode()) {
return new LinkedNodeList<T>();
}
// Create the new list
LinkedNodeList<T> newList = new LinkedNodeList<T>();
newList.head = next;
// Update the head and tail of the new list so that they point to each
// other.
newList.head.prev = list.head.prev; // new list: tail<-head
newList.head.prev.next = newList.head; // new list: tail->head
next = list.head; // old list: tail->head
list.head.prev = getThis(); // old list: tail<-head
// Update all the nodes in the new list so that they know of their new
// list owner.
T n = newList.head;
do {
n.list = newList;
n = n.next;
newList.size++;
list.size--;
} while (n != newList.head);
return newList;
}
/**
* Splits the list into 2 lists. This node becomes the head of this list.
* Then 2nd list is returned.
*
* @return An empty list if this is a head node.
*/
public LinkedNodeList<T> splitBefore() {
if (isHeadNode()) {
return new LinkedNodeList<T>();
}
// Create the new list
LinkedNodeList<T> newList = new LinkedNodeList<T>();
newList.head = list.head;
list.head = getThis();
T newListTail = prev;
prev = newList.head.prev; // old list: tail<-head
prev.next = getThis(); // old list: tail->head
newList.head.prev = newListTail; // new list: tail<-head
newListTail.next = newList.head; // new list: tail->head
// Update all the nodes in the new list so that they know of their new
// list owner.
T n = newList.head;
do {
n.list = newList;
n = n.next;
newList.size++;
list.size--;
} while (n != newList.head);
return newList;
}
public boolean isLinked() {
return list != null;
}
public LinkedNodeList<T> getList() {
return list;
}
}