/*
* The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
* (the "License"). You may not use this work except in compliance with the License, which is
* available at www.apache.org/licenses/LICENSE-2.0
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
* either express or implied, as more fully set forth in the License.
*
* See the NOTICE file distributed with this work for information regarding copyright ownership.
*/
package alluxio.client;
import java.io.IOException;
/**
* Stream that permits positional reading.
*/
public interface PositionedReadable {
/**
* Reads up to the specified number of bytes, from a given position within a file, and return the
* number of bytes read. This does not change the current offset of a file, and is thread-safe.
*
* Not all implementations meet the thread safety requirement. According to the documentation of
* the PositionedReadable interface in Hadoop, those that do not meet the requirement cannot
* be used as a backing store for some applications, such as Apache HBase.
*
* All implementations of this interface in Alluxio must meet the thread safety requirement.
*
* @param position position within file
* @param buffer destination buffer
* @param offset offset in the buffer
* @param length number of bytes to read
* @return actual number of bytes read; -1 means "EOF";
*/
int positionedRead(long position, byte[] buffer, int offset, int length) throws IOException;
}