content: package org.apache.lucene.index;
  
  /**
   * 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.
   */
  
  import java.io.IOException;
  
  import org.apache.lucene.store.Directory;
  
  /**
   * Provides a {@link DirPayloadProcessor} to be used for a {@link Directory}.
   * This allows using different {@link DirPayloadProcessor}s for different
   * directories, for e.g. to perform different processing of payloads of
   * different directories.
   * <p>
   * <b>NOTE:</b> to avoid processing payloads of certain directories, you can
   * return <code>null</code> in {@link #getDirProcessor}.
   * <p>
   * <b>NOTE:</b> it is possible that the same {@link DirPayloadProcessor} will be
   * requested for the same {@link Directory} concurrently. Therefore, to avoid
   * concurrency issues you should return different instances for different
   * threads. Usually, if your {@link DirPayloadProcessor} does not maintain state
   * this is not a problem. The merge code ensures that the
   * {@link DirPayloadProcessor} instance you return will be accessed by one
   * thread to obtain the {@link PayloadProcessor}s for different terms.
   * 
   * @lucene.experimental
   */
  public abstract class PayloadProcessorProvider {
  
    /**
     * Returns a {@link PayloadProcessor} for a given {@link Term} which allows
     * processing the payloads of different terms differently. If you intent to
     * process all your payloads the same way, then you can ignore the given term.
     * <p>
     * <b>NOTE:</b> if you protect your {@link DirPayloadProcessor} from
     * concurrency issues, then you shouldn't worry about any such issues when
     * {@link PayloadProcessor}s are requested for different terms.
     */
    public static abstract class DirPayloadProcessor {
  
      /** Returns a {@link PayloadProcessor} for the given term. */
      public abstract PayloadProcessor getProcessor(Term term) throws IOException;
      
    }
  
    /**
     * Processes the given payload. One should call {@link #payloadLength()} to
     * get the length of the processed payload.
     * 
     * @lucene.experimental
     */
    public static abstract class PayloadProcessor {
  
      /** Returns the length of the payload that was returned by {@link #processPayload}. */
      public abstract int payloadLength() throws IOException;
  
      /**
       * Process the incoming payload and returns the resulting byte[]. Note that
       * a new array might be allocated if the given array is not big enough. The
       * length of the new payload data can be obtained via
       * {@link #payloadLength()}.
       */
      public abstract byte[] processPayload(byte[] payload, int start, int length) throws IOException;
  
    }
  
    /**
     * Returns a {@link DirPayloadProcessor} for the given {@link Directory},
     * through which {@link PayloadProcessor}s can be obtained for each
     * {@link Term}, or <code>null</code> if none should be used.
     */
    public abstract DirPayloadProcessor getDirProcessor(Directory dir) throws IOException;
  
  }
  