/*
* This file is part of NucleusFramework for Bukkit, licensed under the MIT License (MIT).
*
* Copyright (c) JCThePants (www.jcwhatever.com)
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.jcwhatever.nucleus.collections;
import com.jcwhatever.nucleus.utils.PreCon;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import javax.annotation.Nullable;
/**
* A collection with weak references to its elements.
* Uses an {@link java.util.ArrayList} internally.
*
* <p>Automatically removes items that have been garbage collected.</p>
*
* @param <E> List element type
*/
public class WeakCollection<E> implements Collection<E> {
private final transient List<ListEntry<E>> _list;
/**
* Constructor.
*/
public WeakCollection() {
this(10);
}
/**
* Constructor.
*
* @param size The initial capacity.
*/
public WeakCollection(int size) {
_list = new ArrayList<>(size);
}
/**
* The number of elements in the collection.
*/
@Override
public int size() {
Iterator<ListEntry<E>> iterator = _list.iterator();
int result = 0;
while (iterator.hasNext()) {
ListEntry<E> entry = iterator.next();
E entryRef = entry.get();
if (entryRef == null) {
iterator.remove();
} else {
result++;
}
}
return result;
}
/**
* Determine if the collection is empty.
*/
@Override
public boolean isEmpty() {
Iterator<ListEntry<E>> iterator = _list.iterator();
while (iterator.hasNext()) {
ListEntry<E> entry = iterator.next();
E entryRef = entry.get();
if (entryRef == null) {
iterator.remove();
} else {
return false;
}
}
return true;
}
/**
* Clear all elements.
*/
@Override
public void clear() {
_list.clear();
}
/**
* Determine if the collection contains
* the specified object.
*
* @param object The object.
*/
@Override
public boolean contains(Object object) {
PreCon.notNull(object);
Iterator<ListEntry<E>> iterator = _list.iterator();
while (iterator.hasNext()) {
ListEntry<E> entry = iterator.next();
E entryRef = entry.get();
if (entryRef == null) {
iterator.remove();
} else if (entryRef.equals(object)) {
return true;
}
}
return false;
}
/**
* Convert the collection to an array.
*/
@Override
public Object[] toArray() {
List<E> list = toList();
Object[] items = new Object[list.size()];
for (int i=0; i < items.length; i++) {
items[i] = list.get(i);
}
return items;
}
/**
* Copy the collection elements to an array.
*/
@Override
public <T> T[] toArray(T[] array) {
PreCon.notNull(array);
//noinspection SuspiciousToArrayCall
return toList().toArray(array);
}
/**
* Add an element
*/
@Override
public boolean add(E element) {
PreCon.notNull(element);
return _list.add(new ListEntry<E>(element));
}
/**
* Remove an element.
*/
@Override
public boolean remove(Object object) {
PreCon.notNull(object);
Iterator<ListEntry<E>> iterator = _list.iterator();
while (iterator.hasNext()) {
ListEntry<E> entry = iterator.next();
E entryRef = entry.get();
if (entryRef == null) {
iterator.remove();
continue;
}
if (entryRef.equals(object)) {
iterator.remove();
return true;
}
}
return false;
}
/**
* Determine if all items in the specified collection are present.
*/
@Override
public boolean containsAll(Collection<?> collection) {
PreCon.notNull(collection);
for (Object item : collection) {
if (!contains(item))
return false;
}
return true;
}
/**
* Add all items from a collection.
*/
@Override
public boolean addAll(Collection<? extends E> collection) {
PreCon.notNull(collection);
for (E entry : collection)
add(entry);
return true;
}
/**
* Remove all items that are present in the
* specified collection.
*/
@Override
public boolean removeAll(Collection<?> collection) {
PreCon.notNull(collection);
Iterator<ListEntry<E>> iterator = _list.iterator();
boolean isChanged = false;
while (iterator.hasNext()) {
ListEntry<E> entry = iterator.next();
E entryRef = entry.get();
if (entryRef == null) {
iterator.remove();
continue;
}
if (collection.contains(entryRef)) {
iterator.remove();
isChanged = true;
}
}
return isChanged;
}
/**
* Retain only the items present in the specified
* collection.
*/
@Override
public boolean retainAll(Collection<?> collection) {
PreCon.notNull(collection);
Iterator<ListEntry<E>> iterator = _list.iterator();
boolean isChanged = false;
while (iterator.hasNext()) {
ListEntry<E> entry = iterator.next();
E entryRef = entry.get();
if (entryRef == null) {
iterator.remove();
continue;
}
if (!collection.contains(entryRef)) {
iterator.remove();
isChanged = true;
}
}
return isChanged;
}
/**
* Copy the collection elements into a {@link List}.
*/
public List<E> toList() {
List<E> result = new ArrayList<>(_list.size());
Iterator<ListEntry<E>> iterator = _list.iterator();
while (iterator.hasNext()) {
ListEntry<E> entry = iterator.next();
E entryRef = entry.get();
if (entryRef == null) {
iterator.remove();
continue;
}
result.add(entryRef);
}
return result;
}
/**
* Get an element iterator.
*/
@Override
public Iterator<E> iterator() {
return new WeakIterator();
}
private static class ListEntry<T> extends WeakReference<T> {
private int hash;
public ListEntry(T referent) {
super(referent);
hash = referent.hashCode();
}
@Override
public int hashCode() {
T entry = get();
return entry == null ? hash : entry.hashCode();
}
@Override
public boolean equals(Object object) {
if (object == null)
return false;
T entry = get();
if (entry == null)
return false;
if (object instanceof ListEntry) {
return entry.equals(((ListEntry)object).get()) || object == this;
}
return entry.equals(object);
}
}
private class WeakIterator implements Iterator<E> {
ListIterator<ListEntry<E>> iterator = _list.listIterator(0);
E currentRef;
@Override
public boolean hasNext() {
if (!iterator.hasNext())
return false;
ListEntry<E> entry = iterator.next();
currentRef = entry.get();
if (currentRef == null)
return false;
iterator.previous();
return true;
}
@Override
@Nullable
public E next() {
ListEntry<E> entry = iterator.next();
return currentRef = entry.get();
}
@Override
public void remove() {
iterator.remove();
}
}
}