/**
* 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.
*/
package org.apache.hadoop.hdfs;
import java.io.IOException;
import java.net.Socket;
/**
* A BlockReader is responsible for reading a single block
* from a single datanode.
*/
public interface BlockReader {
/* same interface as inputStream java.io.InputStream#read()
* used by DFSInputStream#read()
* This violates one rule when there is a checksum error:
* "Read should not modify user buffer before successful read"
* because it first reads the data to user buffer and then checks
* the checksum.
*/
int read(byte[] buf, int off, int len) throws IOException;
/**
* Skip the given number of bytes
*/
long skip(long n) throws IOException;
void close() throws IOException;
/**
* Read exactly the given amount of data, throwing an exception
* if EOF is reached before that amount
*/
void readFully(byte[] buf, int readOffset, int amtToRead) throws IOException;
/**
* Similar to {@link #readFully(byte[], int, int)} except that it will
* not throw an exception on EOF. However, it differs from the simple
* {@link #read(byte[], int, int)} call in that it is guaranteed to
* read the data if it is available. In other words, if this call
* does not throw an exception, then either the buffer has been
* filled or the next call will return EOF.
*/
int readAll(byte[] buf, int offset, int len) throws IOException;
/**
* Take the socket used to talk to the DN.
*/
Socket takeSocket();
/**
* Whether the BlockReader has reached the end of its input stream
* and successfully sent a status code back to the datanode.
*/
boolean hasSentStatusCode();
}