content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.master.file.meta;
  
  import alluxio.collections.DelegatingSet;
  import alluxio.master.journal.checkpoint.CheckpointInputStream;
  import alluxio.master.journal.checkpoint.CheckpointOutputStream;
  import alluxio.master.journal.checkpoint.CheckpointType;
  import alluxio.master.journal.checkpoint.Checkpointed;
  import alluxio.master.journal.checkpoint.LongsCheckpointFormat.LongsCheckpointReader;
  
  import java.io.IOException;
  import java.io.OutputStream;
  import java.util.Optional;
  import java.util.concurrent.ConcurrentHashMap;
  import javax.annotation.concurrent.ThreadSafe;
  
  /**
   * A concurrent hash set of Long values that supports writing to and restoring from checkpoints.
   */
  @ThreadSafe
  public abstract class CheckpointedIdHashSet extends DelegatingSet<Long> implements Checkpointed {
    /**
     * Constructs a new checkpointed id hash set.
     */
    public CheckpointedIdHashSet() {
      super(ConcurrentHashMap.newKeySet());
    }
  
    @Override
    public void writeToCheckpoint(OutputStream output) throws IOException {
      CheckpointOutputStream cos = new CheckpointOutputStream(output, CheckpointType.LONGS);
      for (Long id : this) {
        cos.writeLong(id);
      }
    }
  
    @Override
    public void restoreFromCheckpoint(CheckpointInputStream input) throws IOException {
      clear();
      LongsCheckpointReader reader = new LongsCheckpointReader(input);
      Optional<Long> longOpt;
      while ((longOpt = reader.nextLong()).isPresent()) {
        add(longOpt.get());
      }
    }
  }
  