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.io.hfile;
019
020import java.io.IOException;
021
022import org.apache.hadoop.fs.FSDataInputStream;
023import org.apache.yetus.audience.InterfaceAudience;
024
025@InterfaceAudience.Private
026class HFileUtil {
027
028  /** guards against NullPointer
029   * utility which tries to seek on the DFSIS and will try an alternative source
030   * if the FSDataInputStream throws an NPE HBASE-17501
031   * @param istream
032   * @param offset
033   * @throws IOException
034   */
035  static public void seekOnMultipleSources(FSDataInputStream istream, long offset) throws IOException {
036    try {
037      // attempt to seek inside of current blockReader
038      istream.seek(offset);
039    } catch (NullPointerException e) {
040      // retry the seek on an alternate copy of the data
041      // this can occur if the blockReader on the DFSInputStream is null
042      istream.seekToNewSource(offset);
043    }
044  }
045}