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.kafka.storage.internals.checkpoint;
  
  import org.apache.kafka.server.common.CheckpointFile.EntryFormatter;
  import org.apache.kafka.storage.internals.log.EpochEntry;
  import org.apache.kafka.storage.internals.log.LogDirFailureChannel;
  
  import java.io.File;
  import java.io.IOException;
  import java.util.Collection;
  import java.util.List;
  import java.util.Optional;
  import java.util.regex.Pattern;
  
  /**
   * This class persists a map of (LeaderEpoch => Offsets) to a file (for a certain replica)
   * <p>
   * The format in the LeaderEpoch checkpoint file is like this:
   * -----checkpoint file begin------
   * 0                <- LeaderEpochCheckpointFile.currentVersion
   * 2                <- following entries size
   * 0  1     <- the format is: leader_epoch(int32) start_offset(int64)
   * 1  2
   * -----checkpoint file end----------
   */
  public class LeaderEpochCheckpointFile {
  
      public static final Formatter FORMATTER = new Formatter();
  
      private static final String LEADER_EPOCH_CHECKPOINT_FILENAME = "leader-epoch-checkpoint";
      private static final Pattern WHITE_SPACES_PATTERN = Pattern.compile("\\s+");
      private static final int CURRENT_VERSION = 0;
  
      private final CheckpointFileWithFailureHandler<EpochEntry> checkpoint;
  
      public LeaderEpochCheckpointFile(File file, LogDirFailureChannel logDirFailureChannel) throws IOException {
          checkpoint = new CheckpointFileWithFailureHandler<>(file, CURRENT_VERSION, FORMATTER, logDirFailureChannel, file.getParentFile().getParent());
      }
  
      public void write(Collection<EpochEntry> epochs) {
          checkpoint.write(epochs);
      }
  
      public void writeIfDirExists(Collection<EpochEntry> epochs) {
          // Writing epoch entries after truncation is done asynchronously for performance reasons.
          // This could cause NoSuchFileException when the directory is renamed concurrently for topic deletion,
          // so we use writeIfDirExists here.
          checkpoint.writeIfDirExists(epochs);
      }
  
      public List<EpochEntry> read() {
          return checkpoint.read();
      }
  
      public static File newFile(File dir) {
          return new File(dir, LEADER_EPOCH_CHECKPOINT_FILENAME);
      }
  
      private static class Formatter implements EntryFormatter<EpochEntry> {
  
          public String toString(EpochEntry entry) {
              return entry.epoch + " " + entry.startOffset;
          }
  
          public Optional<EpochEntry> fromString(String line) {
              String[] strings = WHITE_SPACES_PATTERN.split(line);
              return (strings.length == 2) ? Optional.of(new EpochEntry(Integer.parseInt(strings[0]), Long.parseLong(strings[1]))) : Optional.empty();
          }
      }
  }
  