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     */
018    package org.apache.hadoop.fs;
019    
020    import org.apache.commons.lang.builder.EqualsBuilder;
021    import org.apache.commons.lang.builder.HashCodeBuilder;
022    import org.apache.hadoop.classification.InterfaceAudience;
023    import org.apache.hadoop.classification.InterfaceStability;
024    import org.apache.hadoop.util.StringUtils;
025    
026    import com.google.common.base.Preconditions;
027    
028    /**
029     * HDFS-specific volume identifier which implements {@link VolumeId}. Can be
030     * used to differentiate between the data directories on a single datanode. This
031     * identifier is only unique on a per-datanode basis.
032     */
033    @InterfaceStability.Unstable
034    @InterfaceAudience.Public
035    public class HdfsVolumeId implements VolumeId {
036      
037      private final byte[] id;
038    
039      public HdfsVolumeId(byte[] id) {
040        Preconditions.checkNotNull(id, "id cannot be null");
041        this.id = id;
042      }
043    
044      @Override
045      public int compareTo(VolumeId arg0) {
046        if (arg0 == null) {
047          return 1;
048        }
049        return hashCode() - arg0.hashCode();
050      }
051    
052      @Override
053      public int hashCode() {
054        return new HashCodeBuilder().append(id).toHashCode();
055      }
056    
057      @Override
058      public boolean equals(Object obj) {
059        if (obj == null || obj.getClass() != getClass()) {
060          return false;
061        }
062        if (obj == this) {
063          return true;
064        }
065        HdfsVolumeId that = (HdfsVolumeId) obj;
066        return new EqualsBuilder().append(this.id, that.id).isEquals();
067      }
068    
069      @Override
070      public String toString() {
071        return StringUtils.byteToHexString(id);
072      }
073    }