/*******************************************************************************
* Copyright (c) 1998, 2015 Oracle and/or its affiliates. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
* which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Oracle - initial API and implementation from Oracle TopLink
******************************************************************************/
package org.eclipse.persistence.internal.helper.linkedlist;
import java.util.*;
import org.eclipse.persistence.exceptions.ValidationException;
/**
* INTERNAL:
* A custom implementation of a linked list. This list exposes the linked nodes
* directly to the developer. It allows nodes to be referenced in code for quick
* list manipulation (ie reshuffle, remove, or queuing)
* It is specifically used in the EclipseLink cache write lock mechanism in order
* to allow quick removal of objects from the list while still providing the getFirst()
* addLast() functionality of a queue. The alternative java classes LinkedList, LinkedHashMap
* do not provide both functional requirements.
* @author Gordon Yorke
* @since 10.0.3
* @see org.eclipse.persistence.internal.helper.linkedlist.LinkedNode
*/
public class ExposedNodeLinkedList implements List {
private transient LinkedNode header;
private transient int size;
/**
* Constructs an empty list.
*/
public ExposedNodeLinkedList() {
this.size = 0;
this.header = new LinkedNode(null, null, null);
header.next = header;
header.previous = header;
}
// Bunch of List methods not currently implemented.
public Object[] toArray(Object[] array) {
throw ValidationException.operationNotSupported("toArray");
}
public Object[] toArray() {
throw ValidationException.operationNotSupported("toArray");
}
public Object set(int index, Object value) {
throw ValidationException.operationNotSupported("set");
}
public ListIterator listIterator(int index) {
throw ValidationException.operationNotSupported("listIterator");
}
public ListIterator listIterator() {
throw ValidationException.operationNotSupported("listIterator");
}
public Iterator iterator() {
throw ValidationException.operationNotSupported("iterator");
}
public List subList(int start, int end) {
throw ValidationException.operationNotSupported("subList");
}
public boolean retainAll(Collection collection) {
throw ValidationException.operationNotSupported("retainAll");
}
public boolean removeAll(Collection collection) {
throw ValidationException.operationNotSupported("removeAll");
}
public boolean containsAll(Collection collection) {
throw ValidationException.operationNotSupported("containsAll");
}
public boolean addAll(Collection collection) {
throw ValidationException.operationNotSupported("addAll");
}
public boolean addAll(int index, Collection collection) {
throw ValidationException.operationNotSupported("addAll");
}
public boolean remove(Object object) {
throw ValidationException.operationNotSupported("remove");
}
public boolean add(Object object) {
addLast(object);
return true;
}
public int lastIndexOf(Object object) {
throw ValidationException.operationNotSupported("lastIndexOf");
}
public void add(int index, Object object) {
throw ValidationException.operationNotSupported("add");
}
public Object remove(int index) {
throw ValidationException.operationNotSupported("remove");
}
public Object get(int index) {
throw ValidationException.operationNotSupported("get");
}
public boolean isEmpty() {
return size() == 0;
}
/**
* Returns the first contents in this list.
*
* @return the first contents in this list. Null if this list is empty.
*/
public Object getFirst() {
if (size == 0) {
return null;
}
return header.next.contents;
}
/**
* Returns the last contents in this list.
*
* @return the last contents in this list. Null if this list is empty.
*/
public Object getLast() {
if (size == 0) {
return null;
}
return header.previous.contents;
}
/**
* Removes and returns the first contents from this list.
*
* @return the first contents from this list.
* @throws NoSuchElementException if this list is empty.
*/
public Object removeFirst() {
if (size != 0) {
Object first = header.next.contents;
remove(header.next);
return first;
}
return null;
}
/**
* Removes and returns the last contents from this list.
*
* @return the last contents from this list.
* @throws NoSuchElementException if this list is empty.
*/
public Object removeLast() {
if (size != 0) {
Object last = header.previous.contents;
remove(header.previous);
return last;
}
return null;
}
/**
* Inserts the given contents at the beginning of this list.
*
* @param o the contents to be inserted at the beginning of this list.
*/
public LinkedNode addFirst(Object o) {
return addAfter(o, header);
}
/**
* Appends the given contents to the end of this list. (Identical in
* function to the <tt>add</tt> method; included only for consistency.)
*
* @param o the contents to be inserted at the end of this list.
*/
public LinkedNode addLast(Object o) {
return addAfter(o, header.previous);
}
/**
* Returns <tt>true</tt> if this list contains the specified contents.
* More formally, returns <tt>true</tt> if and only if this list contains
* at least one contents <tt>e</tt> such that <tt>(o==null ? e==null
* : o.equals(e))</tt>.
*
* @param o contents whose presence in this list is to be tested.
* @return <tt>true</tt> if this list contains the specified contents.
*/
public boolean contains(Object o) {
return indexOf(o) != -1;
}
/**
* Returns the number of contents in this list.
*
* @return the number of contents in this list.
*/
public int size() {
return size;
}
/**
* Removes all of the contents from this list.
*/
public void clear() {
header.next = header;
header.previous = header;
size = 0;
}
/**
* Returns the index in this list of the first occurrence of the
* specified contents, or -1 if the List does not contain this
* contents. More formally, returns the lowest index i such that
* <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, or -1 if
* there is no such index.
*
* @param o contents to search for.
* @return the index in this list of the first occurrence of the
* specified contents, or -1 if the list does not contain this
* contents.
*/
public int indexOf(Object o) {
int index = 0;
if (o == null) {
for (LinkedNode n = header.next; n != header; n = n.next) {
if (n.contents == null) {
return index;
}
index++;
}
} else {
for (LinkedNode n = header.next; n != header; n = n.next) {
if (o.equals(n.contents)) {
return index;
}
index++;
}
}
return -1;
}
private LinkedNode addAfter(Object o, LinkedNode n) {
LinkedNode newNode = new LinkedNode(o, n.next, n);
newNode.previous.next = newNode;
newNode.next.previous = newNode;
size++;
return newNode;
}
/**
* Allows a node to be efficiently removed.
*/
public void remove(LinkedNode n) {
if (n == header) {
throw new NoSuchElementException();
} else if ((n.previous == null) || (n.next == null)) {
// Handles case of node having already been removed.
return;
}
n.previous.next = n.next;
n.next.previous = n.previous;
// Also clear the nodes references to know that it has been removed.
n.previous = null;
n.next = null;
n.contents = null;
size--;
}
/**
* Allows a node to be efficiently moved first.
*/
public void moveFirst(LinkedNode node) {
if (node == header) {
throw new NoSuchElementException();
} else if ((node.previous == null) || (node.next == null)) {
// Handles case of node having already been removed.
size++;
} else {
node.previous.next = node.next;
node.next.previous = node.previous;
}
node.next = header.next;
node.previous = header;
header.next = node;
node.next.previous = node;
}
}