TransactionLogReader.java

/*
 * Copyright © 2012-2014 Cask Data, Inc.
 *
 * Licensed 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 co.cask.tephra.persist;

import java.io.Closeable;
import java.io.IOException;

/**
 * Represents a reader for {@link TransactionLog} instances.
 */
public interface TransactionLogReader extends Closeable {
  /**
   * Returns the next {@code TransactionEdit} from the log file, based on the current position, or {@code null}
   * if the end of the file has been reached.
   */
  TransactionEdit next() throws IOException;

  /**
   * Populates {@code reuse} with the next {@code TransactionEdit}, based on the reader's current position in the
   * log file.
   * @param reuse The {@code TransactionEdit} instance to populate with the log entry data.
   * @return The {@code TransactionEdit} instance, or {@code null} if the end of the file has been reached.
   * @throws IOException If an error is encountered reading the log data.
   */
  TransactionEdit next(TransactionEdit reuse) throws IOException;
}