001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.fs;
020
021import java.io.IOException;
022
023import org.apache.hadoop.classification.InterfaceAudience;
024import org.apache.hadoop.classification.InterfaceStability;
025
026@InterfaceAudience.Public
027@InterfaceStability.Evolving
028public interface CanSetReadahead {
029  /**
030   * Set the readahead on this stream.
031   *
032   * @param readahead     The readahead to use.  null means to use the default.
033   * @throws IOException  If there was an error changing the dropBehind
034   *                      setting.
035   *         UnsupportedOperationException  If this stream doesn't support
036   *                                        setting readahead. 
037   */
038  public void setReadahead(Long readahead)
039    throws IOException, UnsupportedOperationException;
040}