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.master.journal.checkpoint.CheckpointInputStream;
  import alluxio.master.journal.checkpoint.CheckpointName;
  import alluxio.master.journal.checkpoint.CheckpointOutputStream;
  import alluxio.master.journal.checkpoint.CheckpointType;
  import alluxio.master.journal.checkpoint.Checkpointed;
  
  import com.google.common.base.Preconditions;
  
  import java.io.IOException;
  import java.io.OutputStream;
  import java.util.concurrent.atomic.LongAdder;
  
  /**
   * A checkpointed long adder.
   */
  public final class InodeCounter extends LongAdder implements Checkpointed {
    private static final long serialVersionUID = 0;
  
    @Override
    public CheckpointName getCheckpointName() {
      return CheckpointName.INODE_COUNTER;
    }
  
    @Override
    public void writeToCheckpoint(OutputStream output) throws IOException, InterruptedException {
      CheckpointOutputStream stream = new CheckpointOutputStream(output, CheckpointType.LONG);
      stream.writeLong(longValue());
      stream.flush();
    }
  
    @Override
    public void restoreFromCheckpoint(CheckpointInputStream input) throws IOException {
      Preconditions.checkState(input.getType() == CheckpointType.LONG,
          "Unexpected checkpoint type: %s", input.getType());
      reset();
      add(input.readLong());
    }
  }
  