alluxio.worker.block.io

Class LocalFileBlockReader

java.lang.Object

alluxio.worker.block.io.BlockClient

alluxio.worker.block.io.BlockReader

alluxio.worker.block.io.LocalFileBlockReader

All Implemented Interfaces:

Closeable, AutoCloseable

Direct Known Subclasses:

StoreBlockReader

@NotThreadSafe
public class LocalFileBlockReader
extends BlockReader

This class provides read access to a block data file locally stored in managed storage.

Nested Class Summary

Nested classes/interfaces inherited from class alluxio.worker.block.io.BlockClient

BlockClient.Type

Constructor Summary

Constructors

Constructor and Description
LocalFileBlockReader(String path) Constructs a Block reader given the file path of the block.

Method Summary

Modifier and Type	Method and Description
void	close()
void	decreaseUsageCount() decrease the file reader usage count.
ReadableByteChannel	getChannel() Returns a readable byte channel of the block.
String	getFilePath()
long	getLength() Gets the length of the block in bytes.
String	getLocation()
int	getUsageCount()
void	increaseUsageCount() increase the file reader usage count.
boolean	isClosed()
ByteBuffer	read(long offset, long length) Reads data from the block.
int	transferTo(io.netty.buffer.ByteBuf buf) Transfers data (up to buf.writableBytes()) from this reader to the buffer.

Methods inherited from class alluxio.worker.block.io.BlockClient

toString

Methods inherited from class java.lang.Object

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

Constructor Detail

LocalFileBlockReader

public LocalFileBlockReader(String path)
                     throws IOException

Constructs a Block reader given the file path of the block.

Parameters:

path - file path of the block

Throws:

IOException

Method Detail

getChannel

public ReadableByteChannel getChannel()

Description copied from class: BlockReader

Returns a readable byte channel of the block.

Specified by:

getChannel in class BlockReader

Returns:

channel

getLength

public long getLength()

Description copied from class: BlockReader

Gets the length of the block in bytes.

Specified by:

getLength in class BlockReader

Returns:

the length of the block in bytes

increaseUsageCount

public void increaseUsageCount()

increase the file reader usage count.

decreaseUsageCount

public void decreaseUsageCount()

decrease the file reader usage count.

getUsageCount

public int getUsageCount()

Returns:

the file reader usage count

getFilePath

public String getFilePath()

Returns:

the file path

read

public ByteBuffer read(long offset,
                       long length)
                throws IOException

Description copied from class: BlockReader

Reads data from the block.

Implementation Note

Since this method needs to allocate a buffer inside its implementation, it must not choose a ByteBuffer that needs any kind of explicit de-allocation, e.g. a pooled buffer, because the caller has no means of knowing how and when to properly deallocate the returned buffer.
If explicit de-allocation is desired, use an externally allocated ByteBuf and call BlockReader.transferTo(ByteBuf) instead. It is then the caller's responsibility to de-allocate the buffer.

Specified by:

read in class BlockReader

Parameters:

offset - the offset from starting of the block file in bytes

length - the length of data to read in bytes. If offset + length exceeds the block size, the part of data from offset to the end of block is returned.

Returns:

ByteBuffer the data that was read, empty buffer if offset is at the end of block

Throws:

IOException

transferTo

public int transferTo(io.netty.buffer.ByteBuf buf)
               throws IOException

Description copied from class: BlockReader

Transfers data (up to buf.writableBytes()) from this reader to the buffer.

Specified by:

transferTo in class BlockReader

Parameters:

buf - the byte buffer

Returns:

the number of bytes transferred, -1 if the end of the block is reached

Throws:

IOException

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Overrides:

close in class BlockClient

Throws:

IOException

isClosed

public boolean isClosed()

Specified by:

isClosed in class BlockReader

Returns:

true if this reader is closed

getLocation

public String getLocation()

Specified by:

getLocation in class BlockReader

Returns:

an informational string of the location the reader is reading from