lucene/core/src/java/org/apache/lucene/store/FilterDirectory.java

package org.apache.lucene.store;

/*
 * 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 java.util.Collection;

/** Directory implementation that delegates calls to another directory.
 *  This class can be used to add limitations on top of an existing
 *  {@link Directory} implementation such as
 *  {@link RateLimitedDirectoryWrapper rate limiting} or to add additional
 *  sanity checks for tests. However, if you plan to write your own
 *  {@link Directory} implementation, you should consider extending directly
 *  {@link Directory} or {@link BaseDirectory} rather than try to reuse
 *  functionality of existing {@link Directory}s by extending this class.
 *  @lucene.internal */
public class FilterDirectory extends Directory {

  /** Get the wrapped instance by <code>dir</code> as long as this reader is
   *  an instance of {@link FilterDirectory}.  */
  public static Directory unwrap(Directory dir) {
    while (dir instanceof FilterDirectory) {
      dir = ((FilterDirectory) dir).in;
    }
    return dir;
  }

  protected final Directory in;

  /** Sole constructor, typically called from sub-classes. */
  protected FilterDirectory(Directory in) {
    this.in = in;
  }

  /** Return the wrapped {@link Directory}. */
  public final Directory getDelegate() {
    return in;
  }

  @Override
  public String[] listAll() throws IOException {
    return in.listAll();
  }

  @Override
  public void deleteFile(String name) throws IOException {
    in.deleteFile(name);
  }

  @Override
  public long fileLength(String name) throws IOException {
    return in.fileLength(name);
  }

  @Override
  public IndexOutput createOutput(String name, IOContext context)
      throws IOException {
    return in.createOutput(name, context);
  }

  @Override
  public void sync(Collection<String> names) throws IOException {
    in.sync(names);
  }

  @Override
  public void renameFile(String source, String dest) throws IOException {
    in.renameFile(source, dest);
  }

  @Override
  public IndexInput openInput(String name, IOContext context)
      throws IOException {
    return in.openInput(name, context);
  }

  @Override
  public Lock makeLock(String name) {
    return in.makeLock(name);
  }

  @Override
  public void close() throws IOException {
    in.close();
  }

  @Override
  public String toString() {
    return getClass().getSimpleName() + "(" + in.toString() + ")";
  }

}