/*
* Copyright (c) 2014, 3 Round Stones Inc. Some rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
* - 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.
* - Neither the name of the openrdf.org nor the names of its contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS 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 THE COPYRIGHT OWNER OR 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.
*
*/
package org.openrdf.repository.object.managers.helpers;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.util.AbstractCollection;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
/**
* This Map will remove entries when the value in the map has been cleaned from
* garbage collection.
*
* @author James Leigh
*
* @param <K>
* @param <V>
*/
public class WeakValueMap<K, V> extends AbstractMap<K, V> {
final Map<K, WeakEntry> hash;
final ReferenceQueue<? super V> queue = new ReferenceQueue<V>();
private Set<java.util.Map.Entry<K, V>> entrySet;
private Collection<V> values;
private class WeakEntry extends WeakReference<V> {
private K key;
public WeakEntry(K key, V value) {
super(value, (ReferenceQueue<? super V>) queue);
this.key = key;
if (key == null || value == null) {
throw new NullPointerException();
}
}
public K getKey() {
return key;
}
}
/**
* Constructs an empty <tt>SoftObjectMap</tt> with the specified initial
* capacity and load factor.
*
* @param initialCapacity
* the initial capacity
* @param loadFactor
* the load factor
* @throws IllegalArgumentException
* if the initial capacity is negative or the load factor is
* nonpositive
*/
public WeakValueMap(int initialCapacity, float loadFactor) {
hash = new HashMap<K, WeakEntry>(initialCapacity, loadFactor);
}
/**
* Constructs an empty <tt>SoftObjectMap</tt> with the specified initial
* capacity and the default load factor (0.75).
*
* @param initialCapacity
* the initial capacity.
* @throws IllegalArgumentException
* if the initial capacity is negative.
*/
public WeakValueMap(int initialCapacity) {
hash = new HashMap<K, WeakEntry>(initialCapacity);
}
/**
* Constructs an empty <tt>SoftObjectMap</tt> with the default initial
* capacity (16) and the default load factor (0.75).
*/
public WeakValueMap() {
hash = new HashMap<K, WeakEntry>();
}
/**
* Constructs a new <tt>SoftObjectMap</tt> with the same mappings as the
* specified <tt>Map</tt>. The <tt>SoftObjectMap</tt> is created with
* default load factor (0.75) and an initial capacity sufficient to hold the
* mappings in the specified <tt>Map</tt>.
*
* @param m
* the map whose mappings are to be placed in this map
* @throws NullPointerException
* if the specified map is null
*/
public WeakValueMap(Map<? extends K, ? extends V> m) {
hash = new HashMap<K, WeakEntry>(m.size());
putAll(m);
}
public int size() {
compact();
return hash.size();
}
public boolean isEmpty() {
compact();
return hash.isEmpty();
}
public boolean containsKey(Object key) {
compact();
WeakEntry ref = hash.get(key);
return ref != null && ref.get() != null;
}
public boolean containsValue(Object value) {
compact();
return values().contains(value);
}
public V get(Object key) {
return refGet(hash.get(key));
}
public V put(K key, V value) {
compact();
return refGet(hash.put(key, new WeakEntry(key, value)));
}
public V remove(Object key) {
compact();
return refGet(hash.remove(key));
}
public void putAll(Map<? extends K, ? extends V> m) {
compact();
for (Map.Entry<? extends K, ? extends V> e : m.entrySet()) {
hash.put(e.getKey(), new WeakEntry(e.getKey(), e.getValue()));
}
}
public void clear() {
hash.clear();
}
public Set<K> keySet() {
compact();
return hash.keySet();
}
public synchronized Collection<V> values() {
compact();
if (values != null)
return values;
return values = new AbstractCollection<V>() {
public Iterator<V> iterator() {
return new Iterator<V>() {
private Iterator<WeakEntry> i = hash.values().iterator();
public boolean hasNext() {
return i.hasNext();
}
public V next() {
return refGet(i.next());
}
public void remove() {
i.remove();
}
};
}
public int size() {
return hash.size();
}
public boolean isEmpty() {
return hash.isEmpty();
}
public void clear() {
hash.clear();
}
};
}
public synchronized Set<java.util.Map.Entry<K, V>> entrySet() {
compact();
if (entrySet != null)
return entrySet;
return entrySet = new AbstractSet<Map.Entry<K, V>>() {
public Iterator<java.util.Map.Entry<K, V>> iterator() {
return new Iterator<java.util.Map.Entry<K, V>>() {
Iterator<Entry<K, WeakEntry>> i = hash.entrySet()
.iterator();
public boolean hasNext() {
return i.hasNext();
}
public java.util.Map.Entry<K, V> next() {
return new Entry<K, V>() {
private Entry<K, WeakEntry> entry = i.next();
public K getKey() {
return entry.getKey();
}
public V getValue() {
return refGet(entry.getValue());
}
public V setValue(V value) {
return refGet(entry.setValue(new WeakEntry(
entry.getKey(), value)));
}
};
}
public void remove() {
i.remove();
}
};
}
public int size() {
return hash.size();
}
public boolean isEmpty() {
return hash.isEmpty();
}
public void clear() {
hash.clear();
}
};
}
@SuppressWarnings("unchecked")
private synchronized void compact() {
WeakEntry ref;
while ((ref = (WeakEntry) queue.poll()) != null) {
if (ref == hash.get(ref.getKey())) {
hash.remove(ref.getKey());
}
}
}
V refGet(WeakEntry ref) {
if (ref == null)
return null;
return ref.get();
}
}