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 */
018package org.apache.hadoop.fs;
019
020import java.io.*;
021
022import org.apache.hadoop.classification.InterfaceAudience;
023import org.apache.hadoop.classification.InterfaceStability;
024
025/** Stream that permits positional reading. */
026@InterfaceAudience.Public
027@InterfaceStability.Evolving
028public interface PositionedReadable {
029  /**
030   * Read upto the specified number of bytes, from a given
031   * position within a file, and return the number of bytes read. This does not
032   * change the current offset of a file, and is thread-safe.
033   */
034  public int read(long position, byte[] buffer, int offset, int length)
035    throws IOException;
036  
037  /**
038   * Read the specified number of bytes, from a given
039   * position within a file. This does not
040   * change the current offset of a file, and is thread-safe.
041   */
042  public void readFully(long position, byte[] buffer, int offset, int length)
043    throws IOException;
044  
045  /**
046   * Read number of bytes equal to the length of the buffer, from a given
047   * position within a file. This does not
048   * change the current offset of a file, and is thread-safe.
049   */
050  public void readFully(long position, byte[] buffer) throws IOException;
051}