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Server functionality for HBase

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/*
 * 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.hadoop.hbase.io.hfile;

import org.apache.hadoop.hbase.io.ByteBuffAllocator;
import org.apache.hadoop.hbase.nio.ByteBuff;
import org.apache.yetus.audience.InterfaceAudience;

/**
 * The {@link ByteBuffAllocator} won't allocate pooled heap {@link ByteBuff} now; at the same time,
 * if allocate an off-heap {@link ByteBuff} from allocator, then it must be a pooled one. That's to
 * say, an exclusive memory HFileBlock would must be an heap block and a shared memory HFileBlock
 * would must be an off-heap block.
 * 
 * The exclusive memory HFileBlock will do nothing when calling retain or release methods, because
 * its memory will be garbage collected by JVM, even if its reference count decrease to zero, we can
 * do nothing for the de-allocating.
 * 
 * @see org.apache.hadoop.hbase.io.hfile.SharedMemHFileBlock
 */
@InterfaceAudience.Private
public class ExclusiveMemHFileBlock extends HFileBlock {

  ExclusiveMemHFileBlock(BlockType blockType, int onDiskSizeWithoutHeader,
    int uncompressedSizeWithoutHeader, long prevBlockOffset, ByteBuff buf, boolean fillHeader,
    long offset, int nextBlockOnDiskSize, int onDiskDataSizeWithHeader, HFileContext fileContext,
    ByteBuffAllocator alloc) {
    super(blockType, onDiskSizeWithoutHeader, uncompressedSizeWithoutHeader, prevBlockOffset, buf,
      fillHeader, offset, nextBlockOnDiskSize, onDiskDataSizeWithHeader, fileContext, alloc);
  }

  @Override
  public int refCnt() {
    return 0;
  }

  @Override
  public ExclusiveMemHFileBlock retain() {
    // do nothing
    return this;
  }

  @Override
  public boolean release() {
    // do nothing
    return false;
  }

  @Override
  public boolean isSharedMem() {
    return false;
  }
}