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.apex.malhar.flume.storage;
  
  import com.datatorrent.netlet.util.Slice;
  
  /**
   * <p>Storage interface.</p>
   *
   * @since 0.9.2
   */
  public interface Storage
  {
    /**
     * key in the context for Unique identifier for the storage which may be used to recover from failure.
     */
    String ID = "id";
  
    /**
     * This stores the bytes and returns the unique identifier to retrieve these bytes
     *
     * @param bytes
     * @return
     */
    byte[] store(Slice bytes);
  
    /**
     * This returns the data bytes for the current identifier and the identifier for next data bytes. <br/>
     * The first eight bytes contain the identifier and the remaining bytes contain the data
     *
     * @param identifier
     * @return
     */
    byte[] retrieve(byte[] identifier);
  
    /**
     * This returns data bytes and the identifier for the next data bytes. The identifier for current data bytes is based
     * on the retrieve method call and number of retrieveNext method calls after retrieve method call. <br/>
     * The first eight bytes contain the identifier and the remaining bytes contain the data
     *
     * @return
     */
    byte[] retrieveNext();
  
    /**
     * This is used to clean up the files identified by identifier
     *
     * @param identifier
     */
    void clean(byte[] identifier);
  
    /**
     * This flushes the data from stream
     *
     */
    void flush();
  
  }
  