vy commented on code in PR #3427: URL: https://github.com/apache/logging-log4j2/pull/3427#discussion_r1937623818
########## log4j-core/src/main/java/org/apache/logging/log4j/core/util/internal/WeakValuesHashMap.java: ########## @@ -0,0 +1,121 @@ +/* + * 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.logging.log4j.core.util.internal; + +import java.lang.ref.ReferenceQueue; +import java.lang.ref.WeakReference; +import java.util.AbstractMap; +import java.util.Collection; +import java.util.HashMap; +import java.util.Map; +import java.util.Set; + +/** + * A {@link HashMap} implementation which is similar to {@link java.util.WeakHashMap} but for weak values instead of + * keys. Warning: this is not a general-purpose implementation; only what's needed by @{@link InternalLoggerRegistry} + * is implemented. + * @param <K> - the type of keys maintained by this map + * @param <V> – the type of mapped values + */ +class WeakValuesHashMap<K, V> extends AbstractMap<K, V> { + private final HashMap<K, WeakValue<V>> map; + private final ReferenceQueue<V> queue; + + public WeakValuesHashMap() { + map = new HashMap<>(10); + queue = new ReferenceQueue<>(); + } + + @Override + public V put(K key, V value) { + processQueue(); + WeakValue<V> ref = new WeakValue<>(key, value, queue); + return unref(map.put(key, ref)); + } + + @Override + public V get(Object key) { + processQueue(); + return unref(map.get(key)); + } + + @Override + public V remove(Object key) { + return unref(map.get(key)); + } + + @Override + public void clear() { + map.clear(); + } + + @Override + public boolean containsKey(Object key) { + processQueue(); + return map.containsKey(key); + } + + @Override + public boolean containsValue(Object value) { + throw new UnsupportedOperationException(); + } + + @Override + public Set<K> keySet() { + throw new UnsupportedOperationException(); + } + + @Override + public int size() { + processQueue(); + return map.size(); + } + + @Override + public Set<Map.Entry<K, V>> entrySet() { + throw new UnsupportedOperationException(); + } + + @Override + public Collection<V> values() { + throw new UnsupportedOperationException(); + } + + private V unref(WeakValue<V> valueRef) { + return valueRef == null ? null : valueRef.get(); + } + + @SuppressWarnings("unchecked") + private void processQueue() { + for (WeakValue<V> v = (WeakValue<V>) queue.poll(); v != null; v = (WeakValue<V>) queue.poll()) { + map.remove(v.getKey()); Review Comment: @tristantarrant, methods accessed while holding a read-lock might end up mutating the map, which is not thread-safe. Am I mistaken? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: notifications-unsubscr...@logging.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
