text: /**
   * 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.yarn.server.utils;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.util.Iterator;
  import java.util.Map;
  
  import org.apache.hadoop.classification.InterfaceAudience.Public;
  import org.apache.hadoop.classification.InterfaceStability.Evolving;
  import org.iq80.leveldb.DB;
  import org.iq80.leveldb.DBException;
  import org.iq80.leveldb.DBIterator;
  import org.iq80.leveldb.ReadOptions;
  
  /**
   * A wrapper for a DBIterator to translate the raw RuntimeExceptions that
   * can be thrown into DBExceptions.
   */
  @Public
  @Evolving
  public class LeveldbIterator implements Iterator<Map.Entry<byte[], byte[]>>,
                                          Closeable {
    private DBIterator iter;
  
    /**
     * Create an iterator for the specified database
     */
    public LeveldbIterator(DB db) {
      iter = db.iterator();
    }
  
    /**
     * Create an iterator for the specified database
     */
    public LeveldbIterator(DB db, ReadOptions options) {
      iter = db.iterator(options);
    }
  
    /**
     * Create an iterator using the specified underlying DBIterator
     */
    public LeveldbIterator(DBIterator iter) {
      this.iter = iter;
    }
  
    /**
     * Repositions the iterator so the key of the next BlockElement
     * returned greater than or equal to the specified targetKey.
     */
    public void seek(byte[] key) throws DBException {
      try {
        iter.seek(key);
      } catch (DBException e) {
        throw e;
      } catch (RuntimeException e) {
        throw new DBException(e.getMessage(), e);
      }
    }
  
    /**
     * Repositions the iterator so is is at the beginning of the Database.
     */
    public void seekToFirst() throws DBException {
      try {
        iter.seekToFirst();
      } catch (DBException e) {
        throw e;
      } catch (RuntimeException e) {
        throw new DBException(e.getMessage(), e);
      }
    }
  
    /**
     * Repositions the iterator so it is at the end of of the Database.
     */
    public void seekToLast() throws DBException {
      try {
        iter.seekToLast();
      } catch (DBException e) {
        throw e;
      } catch (RuntimeException e) {
        throw new DBException(e.getMessage(), e);
      }
    }
  
    /**
     * Returns <tt>true</tt> if the iteration has more elements.
     */
    public boolean hasNext() throws DBException {
      try {
        return iter.hasNext();
      } catch (DBException e) {
        throw e;
      } catch (RuntimeException e) {
        throw new DBException(e.getMessage(), e);
      }
    }
  
    /**
     * Returns the next element in the iteration.
     */
    @Override
    public Map.Entry<byte[], byte[]> next() throws DBException {
      try {
        return iter.next();
      } catch (DBException e) {
        throw e;
      } catch (RuntimeException e) {
        throw new DBException(e.getMessage(), e);
      }
    }
  
    /**
     * Returns the next element in the iteration, without advancing the
     * iteration.
     */
    public Map.Entry<byte[], byte[]> peekNext() throws DBException {
      try {
        return iter.peekNext();
      } catch (DBException e) {
        throw e;
      } catch (RuntimeException e) {
        throw new DBException(e.getMessage(), e);
      }
    }
  
    /**
     * @return true if there is a previous entry in the iteration.
     */
    public boolean hasPrev() throws DBException {
      try {
        return iter.hasPrev();
      } catch (DBException e) {
        throw e;
      } catch (RuntimeException e) {
        throw new DBException(e.getMessage(), e);
      }
    }
  
    /**
     * @return the previous element in the iteration and rewinds the iteration.
     */
    public Map.Entry<byte[], byte[]> prev() throws DBException {
      try {
        return iter.prev();
      } catch (DBException e) {
        throw e;
      } catch (RuntimeException e) {
        throw new DBException(e.getMessage(), e);
      }
    }
  
    /**
     * @return the previous element in the iteration, without rewinding the
     * iteration.
     */
    public Map.Entry<byte[], byte[]> peekPrev() throws DBException {
      try {
        return iter.peekPrev();
      } catch (DBException e) {
        throw e;
      } catch (RuntimeException e) {
        throw new DBException(e.getMessage(), e);
      }
    }
  
    /**
     * Removes from the database the last element returned by the iterator.
     */
    @Override
    public void remove() throws DBException {
      try {
        iter.remove();
      } catch (DBException e) {
        throw e;
      } catch (RuntimeException e) {
        throw new DBException(e.getMessage(), e);
      }
    }
  
    /**
     * Closes the iterator.
     */
    @Override
    public void close() throws IOException {
      try {
        iter.close();
      } catch (RuntimeException e) {
        throw new IOException(e.getMessage(), e);
      }
    }
  }
  