| /* |
| * 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.lucene.util; |
| |
| import java.io.IOException; |
| import java.util.concurrent.atomic.AtomicInteger; |
| |
| |
| /** |
| * Manages reference counting for a given object. Extensions can override |
| * {@link #release()} to do custom logic when reference counting hits 0. |
| */ |
| public class RefCount<T> { |
| |
| private final AtomicInteger refCount = new AtomicInteger(1); |
| |
| protected final T object; |
| |
| public RefCount(T object) { |
| this.object = object; |
| } |
| |
| /** |
| * Called when reference counting hits 0. By default this method does nothing, |
| * but extensions can override to e.g. release resources attached to object |
| * that is managed by this class. |
| */ |
| protected void release() throws IOException {} |
| |
| /** |
| * Decrements the reference counting of this object. When reference counting |
| * hits 0, calls {@link #release()}. |
| */ |
| public final void decRef() throws IOException { |
| final int rc = refCount.decrementAndGet(); |
| if (rc == 0) { |
| boolean success = false; |
| try { |
| release(); |
| success = true; |
| } finally { |
| if (!success) { |
| // Put reference back on failure |
| refCount.incrementAndGet(); |
| } |
| } |
| } else if (rc < 0) { |
| throw new IllegalStateException("too many decRef calls: refCount is " + rc + " after decrement"); |
| } |
| } |
| |
| public final T get() { |
| return object; |
| } |
| |
| /** Returns the current reference count. */ |
| public final int getRefCount() { |
| return refCount.get(); |
| } |
| |
| /** |
| * Increments the reference count. Calls to this method must be matched with |
| * calls to {@link #decRef()}. |
| */ |
| public final void incRef() { |
| refCount.incrementAndGet(); |
| } |
| |
| } |
| |