/*
* JBoss, Home of Professional Open Source.
* Copyright 2011, Red Hat, Inc., and individual contributors
* as indicated by the @author tags. See the copyright.txt file in the
* distribution for a full listing of individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.jboss.as.controller.registry;
import java.util.Collections;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
import org.wildfly.common.Assert;
/**
* @author <a href="mailto:david.lloyd@redhat.com">David M. Lloyd</a>
*/
final class AtomicMapFieldUpdater<C, K, V> {
private final AtomicReferenceFieldUpdater<C, Map<K, V>> updater;
@SuppressWarnings( { "unchecked" })
public static <C, K, V> AtomicMapFieldUpdater<C, K, V> newMapUpdater(AtomicReferenceFieldUpdater<C, Map> updater) {
return new AtomicMapFieldUpdater<C, K, V>(updater);
}
@SuppressWarnings( { "unchecked" })
AtomicMapFieldUpdater(AtomicReferenceFieldUpdater<C, Map> updater) {
this.updater = (AtomicReferenceFieldUpdater) updater;
}
public void clear(C instance) {
updater.set(instance, Collections.<K, V>emptyMap());
}
public V get(C instance, Object key) {
return updater.get(instance).get(key);
}
public V put(C instance, K key, V value) {
Assert.checkNotNullParam("key", key);
for (;;) {
final Map<K, V> oldMap = updater.get(instance);
final Map<K, V> newMap;
final V oldValue;
final int oldSize = oldMap.size();
if (oldSize == 0) {
oldValue = null;
newMap = Collections.singletonMap(key, value);
} else if (oldSize == 1) {
final Map.Entry<K, V> entry = oldMap.entrySet().iterator().next();
final K oldKey = entry.getKey();
if (oldKey.equals(key)) {
newMap = Collections.singletonMap(key, value);
oldValue = entry.getValue();
} else {
newMap = new FastCopyHashMap<K, V>(oldMap);
oldValue = newMap.put(key, value);
}
} else {
newMap = new FastCopyHashMap<K, V>(oldMap);
oldValue = newMap.put(key, value);
}
final boolean result = updater.compareAndSet(instance, oldMap, newMap);
if (result) {
return oldValue;
}
}
}
/**
* Put a value if and only if the map has not changed since the given snapshot was taken. If the put fails,
* it is the caller's responsibility to retry.
*
* @param instance the instance with the map field
* @param key the key
* @param value the value
* @param snapshot the map snapshot
* @return {@code false} if the snapshot is out of date and we could not update, {@code true} if the put succeeded
*/
public boolean putAtomic(C instance, K key, V value, Map<K, V> snapshot) {
Assert.checkNotNullParam("key", key);
final Map<K, V> newMap;
final int oldSize = snapshot.size();
if (oldSize == 0) {
newMap = Collections.singletonMap(key, value);
} else if (oldSize == 1) {
final Map.Entry<K, V> entry = snapshot.entrySet().iterator().next();
final K oldKey = entry.getKey();
if (oldKey.equals(key)) {
return false;
} else {
newMap = new FastCopyHashMap<K, V>(snapshot);
newMap.put(key, value);
}
} else {
newMap = new FastCopyHashMap<K, V>(snapshot);
newMap.put(key, value);
}
return updater.compareAndSet(instance, snapshot, newMap);
}
public V putIfAbsent(C instance, K key, V value) {
Assert.checkNotNullParam("key", key);
for (;;) {
final Map<K, V> oldMap = updater.get(instance);
final Map<K, V> newMap;
final int oldSize = oldMap.size();
if (oldSize == 0) {
newMap = Collections.singletonMap(key, value);
} else if (oldSize == 1) {
final Map.Entry<K, V> entry = oldMap.entrySet().iterator().next();
final K oldKey = entry.getKey();
if (oldKey.equals(key)) {
return entry.getValue();
} else {
newMap = new FastCopyHashMap<K, V>(oldMap);
newMap.put(key, value);
}
} else {
if (oldMap.containsKey(key)) {
return oldMap.get(key);
}
newMap = new FastCopyHashMap<K, V>(oldMap);
newMap.put(key, value);
}
if (updater.compareAndSet(instance, oldMap, newMap)) {
return null;
}
}
}
public V remove(C instance, K key) {
if (key == null) {
return null;
}
for (;;) {
final Map<K, V> oldMap = updater.get(instance);
final Map<K, V> newMap;
final V oldValue;
final int oldSize = oldMap.size();
if (oldSize == 0) {
return null;
} else if (oldSize == 1) {
final Map.Entry<K, V> entry = oldMap.entrySet().iterator().next();
if (entry.getKey().equals(key)) {
newMap = Collections.emptyMap();
oldValue = entry.getValue();
} else {
return null;
}
} else if (oldSize == 2) {
final Iterator<Map.Entry<K,V>> i = oldMap.entrySet().iterator();
final Map.Entry<K, V> entry = i.next();
final Map.Entry<K, V> next = i.next();
if (entry.getKey().equals(key)) {
newMap = Collections.singletonMap(next.getKey(), next.getValue());
oldValue = entry.getValue();
} else if (next.getKey().equals(key)) {
newMap = Collections.singletonMap(entry.getKey(), entry.getValue());
oldValue = next.getValue();
} else {
return null;
}
} else {
if (! oldMap.containsKey(key)) {
return null;
}
newMap = new FastCopyHashMap<K, V>(oldMap);
oldValue = newMap.remove(key);
}
if (updater.compareAndSet(instance, oldMap, newMap)) {
return oldValue;
}
}
}
public Map<K, V> get(final C subregistry) {
return updater.get(subregistry);
}
public Map<K, V> getReadOnly(final C subregistry) {
final Map<K, V> snapshot = updater.get(subregistry);
return snapshot instanceof FastCopyHashMap ? Collections.unmodifiableMap(snapshot) : snapshot;
}
}