org.apache.hadoop.hdfs.shortcircuit.ClientMmap.java Source code

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Here is the source code for org.apache.hadoop.hdfs.shortcircuit.ClientMmap.java

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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.hdfs.shortcircuit;

import org.apache.hadoop.classification.InterfaceAudience;

import java.io.Closeable;
import java.nio.MappedByteBuffer;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A reference to a memory-mapped region used by an HDFS client.
 */
@InterfaceAudience.Private
public class ClientMmap implements Closeable {
    static final Logger LOG = LoggerFactory.getLogger(ClientMmap.class);

    /**
     * A reference to the block replica which this mmap relates to.
     */
    private ShortCircuitReplica replica;

    /**
     * The java ByteBuffer object.
     */
    private final MappedByteBuffer map;

    /**
     * Whether or not this ClientMmap anchors the replica into memory while
     * it exists.  Closing an anchored ClientMmap unanchors the replica.
     */
    private final boolean anchored;

    ClientMmap(ShortCircuitReplica replica, MappedByteBuffer map, boolean anchored) {
        this.replica = replica;
        this.map = map;
        this.anchored = anchored;
    }

    /**
     * Close the ClientMmap object.
     */
    @Override
    public void close() {
        if (replica != null) {
            if (anchored) {
                replica.removeNoChecksumAnchor();
            }
            replica.unref();
        }
        replica = null;
    }

    public MappedByteBuffer getMappedByteBuffer() {
        return map;
    }
}