content: /*
   * 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.celeborn.service.deploy.worker.shuffledb;
  
  import java.io.IOException;
  import java.util.Map;
  import java.util.NoSuchElementException;
  
  /** Note: code copied from Apache Spark. */
  public class LevelDBIterator implements DBIterator {
  
    private final org.iq80.leveldb.DBIterator it;
  
    private boolean checkedNext;
  
    private boolean closed;
  
    private Map.Entry<byte[], byte[]> next;
  
    public LevelDBIterator(org.iq80.leveldb.DBIterator it) {
      this.it = it;
    }
  
    @Override
    public boolean hasNext() {
      if (!checkedNext && !closed) {
        next = loadNext();
        checkedNext = true;
      }
      if (!closed && next == null) {
        try {
          close();
        } catch (IOException ioe) {
          throw new RuntimeException(ioe);
        }
      }
      return next != null;
    }
  
    @Override
    public Map.Entry<byte[], byte[]> next() {
      if (!hasNext()) {
        throw new NoSuchElementException();
      }
      checkedNext = false;
      Map.Entry<byte[], byte[]> ret = next;
      next = null;
      return ret;
    }
  
    @Override
    public void close() throws IOException {
      if (!closed) {
        it.close();
        closed = true;
        next = null;
      }
    }
  
    @Override
    public void seek(byte[] key) {
      it.seek(key);
    }
  
    private Map.Entry<byte[], byte[]> loadNext() {
      boolean hasNext = it.hasNext();
      if (!hasNext) {
        return null;
      }
      return it.next();
    }
  }
  