hbase-common/src/main/java/org/apache/hadoop/hbase/nio/RefCnt.java

   1 /**
   2  * Licensed to the Apache Software Foundation (ASF) under one
   3  * or more contributor license agreements.  See the NOTICE file
   4  * distributed with this work for additional information
   5  * regarding copyright ownership.  The ASF licenses this file
   6  * to you under the Apache License, Version 2.0 (the
   7  * "License"); you may not use this file except in compliance
   8  * with the License.  You may obtain a copy of the License at
   9  *
  10  *     http://www.apache.org/licenses/LICENSE-2.0
  11  *
  12  * Unless required by applicable law or agreed to in writing, software
  13  * distributed under the License is distributed on an "AS IS" BASIS,
  14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15  * See the License for the specific language governing permissions and
  16  * limitations under the License.
  17  */
  18 package org.apache.hadoop.hbase.nio;
  19
  20 import org.apache.hadoop.hbase.io.ByteBuffAllocator;
  21 import org.apache.hadoop.hbase.io.ByteBuffAllocator.Recycler;
  22 import org.apache.yetus.audience.InterfaceAudience;
  23
  24 import org.apache.hbase.thirdparty.io.netty.util.AbstractReferenceCounted;
  25 import org.apache.hbase.thirdparty.io.netty.util.ReferenceCounted;
  26
  27 /**
  28  * Maintain an reference count integer inside to track life cycle of {@link ByteBuff}, if the
  29  * reference count become 0, it'll call {@link Recycler#free()} exactly once.
  30  */
  31 @InterfaceAudience.Private
  32 public class RefCnt extends AbstractReferenceCounted {
  33
  34   private Recycler recycler = ByteBuffAllocator.NONE;
  35
  36   /**
  37    * Create an {@link RefCnt} with an initial reference count = 1. If the reference count become
  38    * zero, the recycler will do nothing. Usually, an Heap {@link ByteBuff} will use this kind of
  39    * refCnt to track its life cycle, it help to abstract the code path although it's not really
  40    * needed to track on heap ByteBuff.
  41    */
  42   public static RefCnt create() {
  43     return new RefCnt(ByteBuffAllocator.NONE);
  44   }
  45
  46   public static RefCnt create(Recycler recycler) {
  47     return new RefCnt(recycler);
  48   }
  49
  50   public RefCnt(Recycler recycler) {
  51     this.recycler = recycler;
  52   }
  53
  54   @Override
  55   protected final void deallocate() {
  56     this.recycler.free();
  57   }
  58
  59   @Override
  60   public final ReferenceCounted touch(Object hint) {
  61     throw new UnsupportedOperationException();
  62   }
  63 }