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.bookkeeper.bookie;
  
  import java.io.IOException;
  
  /**
   * Interface to communicate checkpoint progress.
   */
  public interface CheckpointSource {
  
      /**
       * A checkpoint presented a time point. All entries added before this checkpoint are already persisted.
       */
      interface Checkpoint extends Comparable<Checkpoint> {
  
          Checkpoint MAX = new Checkpoint() {
  
              @Override
              public int compareTo(Checkpoint o) {
                  if (o == MAX) {
                      return 0;
                  }
                  return 1;
              }
  
              @Override
              public boolean equals(Object o) {
                  return this == o;
              }
  
              @Override
              public String toString() {
                  return "MAX";
              }
  
          };
  
          Checkpoint MIN = new Checkpoint() {
              @Override
              public int compareTo(Checkpoint o) {
                  if (o == MIN) {
                      return 0;
                  }
                  return -1;
              }
  
              @Override
              public boolean equals(Object o) {
                  return this == o;
              }
  
              @Override
              public String toString() {
                  return "MIN";
              }
          };
      }
  
      /**
       * Request a new a checkpoint.
       *
       * @return checkpoint.
       */
      Checkpoint newCheckpoint();
  
      /**
       * Tell checkpoint source that the checkpoint is completed.
       * If <code>compact</code> is true, the implementation could compact
       * to reduce size of data containing old checkpoints.
       *
       * @param checkpoint
       *          The checkpoint that has been completed
       * @param compact
       *          Flag to compact old checkpoints.
       */
      void checkpointComplete(Checkpoint checkpoint, boolean compact) throws IOException;
  
      CheckpointSource DEFAULT = new CheckpointSource() {
              @Override
              public Checkpoint newCheckpoint() {
                  return Checkpoint.MIN;
              }
  
              @Override
              public void checkpointComplete(Checkpoint checkpoint, boolean compact) {}
          };
  }
  