001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.nio;
019
020import org.apache.hadoop.hbase.io.ByteBuffAllocator;
021import org.apache.hadoop.hbase.io.ByteBuffAllocator.Recycler;
022import org.apache.yetus.audience.InterfaceAudience;
023
024import org.apache.hbase.thirdparty.io.netty.util.AbstractReferenceCounted;
025import org.apache.hbase.thirdparty.io.netty.util.ReferenceCounted;
026
027/**
028 * Maintain an reference count integer inside to track life cycle of {@link ByteBuff}, if the
029 * reference count become 0, it'll call {@link Recycler#free()} exactly once.
030 */
031@InterfaceAudience.Private
032public class RefCnt extends AbstractReferenceCounted {
033
034  private Recycler recycler = ByteBuffAllocator.NONE;
035
036  /**
037   * Create an {@link RefCnt} with an initial reference count = 1. If the reference count become
038   * zero, the recycler will do nothing. Usually, an Heap {@link ByteBuff} will use this kind of
039   * refCnt to track its life cycle, it help to abstract the code path although it's not really
040   * needed to track on heap ByteBuff.
041   */
042  public static RefCnt create() {
043    return new RefCnt(ByteBuffAllocator.NONE);
044  }
045
046  public static RefCnt create(Recycler recycler) {
047    return new RefCnt(recycler);
048  }
049
050  public RefCnt(Recycler recycler) {
051    this.recycler = recycler;
052  }
053
054  @Override
055  protected final void deallocate() {
056    this.recycler.free();
057  }
058
059  @Override
060  public final ReferenceCounted touch(Object hint) {
061    throw new UnsupportedOperationException();
062  }
063}