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    package org.apache.hadoop.fs;
019    
020    import java.io.*;
021    
022    import org.apache.hadoop.classification.InterfaceAudience;
023    import org.apache.hadoop.classification.InterfaceStability;
024    
025    /** Stream that permits positional reading. */
026    @InterfaceAudience.Public
027    @InterfaceStability.Evolving
028    public 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    }