Package org.apache.hadoop.hdfs.client.impl

Class ExternalBlockReader

java.lang.Object

org.apache.hadoop.hdfs.client.impl.ExternalBlockReader

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, org.apache.hadoop.fs.ByteBufferReadable, BlockReader

@Private
public final class ExternalBlockReader
extends java.lang.Object
implements BlockReader

An ExternalBlockReader uses pluggable ReplicaAccessor objects to read from replicas.

Method Summary

Modifier and Type	Method	Description
int	available()	Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without performing network I/O.
void	close()	Close the block reader.
ClientMmap	getClientMmap(java.util.EnumSet<org.apache.hadoop.fs.ReadOption> opts)	Get a ClientMmap object for this BlockReader.
org.apache.hadoop.util.DataChecksum	getDataChecksum()
int	getNetworkDistance()	Return the network distance between local machine and the remote machine.
boolean	isShortCircuit()
int	read(byte[] buf, int off, int len)
int	read(java.nio.ByteBuffer buf)
int	readAll(byte[] buf, int offset, int len)	Similar to BlockReader.readFully(byte[], int, int) except that it will not throw an exception on EOF.
void	readFully(byte[] buf, int offset, int len)	Read exactly the given amount of data, throwing an exception if EOF is reached before that amount
long	skip(long n)	Skip the given number of bytes

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

read

public int read(byte[] buf,
                int off,
                int len)
         throws java.io.IOException

Specified by:

read in interface BlockReader

Throws:

java.io.IOException

read

public int read(java.nio.ByteBuffer buf)
         throws java.io.IOException

Specified by:

read in interface org.apache.hadoop.fs.ByteBufferReadable

Throws:

java.io.IOException

skip

public long skip(long n)
          throws java.io.IOException

Description copied from interface: BlockReader

Skip the given number of bytes

Specified by:

skip in interface BlockReader

Throws:

java.io.IOException

available

public int available()

Description copied from interface: BlockReader

Returns an estimate of the number of bytes that can be read (or skipped over) from this input stream without performing network I/O. This may return more than what is actually present in the block.

Specified by:

available in interface BlockReader

close

public void close()
           throws java.io.IOException

Description copied from interface: BlockReader

Close the block reader.

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface BlockReader

Specified by:

close in interface java.io.Closeable

Throws:

java.io.IOException

readFully

public void readFully(byte[] buf,
                      int offset,
                      int len)
               throws java.io.IOException

Description copied from interface: BlockReader

Read exactly the given amount of data, throwing an exception if EOF is reached before that amount

Specified by:

readFully in interface BlockReader

Throws:

java.io.IOException

readAll

public int readAll(byte[] buf,
                   int offset,
                   int len)
            throws java.io.IOException

Description copied from interface: BlockReader

Similar to BlockReader.readFully(byte[], int, int) except that it will not throw an exception on EOF. However, it differs from the simple BlockReader.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.

Specified by:

readAll in interface BlockReader

Throws:

java.io.IOException

isShortCircuit

public boolean isShortCircuit()

Specified by:

isShortCircuit in interface BlockReader

Returns:

true only if this is a short-circuit read. All short-circuit reads are also local.

getClientMmap

public ClientMmap getClientMmap(java.util.EnumSet<org.apache.hadoop.fs.ReadOption> opts)

Description copied from interface: BlockReader

Get a ClientMmap object for this BlockReader.

Specified by:

getClientMmap in interface BlockReader

Parameters:

opts - The read options to use.

Returns:

The ClientMmap object, or null if mmap is not supported.

getDataChecksum

public org.apache.hadoop.util.DataChecksum getDataChecksum()

Specified by:

getDataChecksum in interface BlockReader

Returns:

The DataChecksum used by the read block

getNetworkDistance

public int getNetworkDistance()

Description copied from interface: BlockReader

Return the network distance between local machine and the remote machine.

Specified by:

getNetworkDistance in interface BlockReader