alluxio.worker.page

Class PagedUfsBlockReader

java.lang.Object

alluxio.worker.block.io.BlockClient

alluxio.worker.block.io.BlockReader

alluxio.worker.page.PagedUfsBlockReader

All Implemented Interfaces:

Closeable, AutoCloseable

public class PagedUfsBlockReader
extends BlockReader

Block reader that reads from UFS.

Nested Class Summary

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

BlockClient.Type

Constructor Summary

Constructors

Constructor and Description
PagedUfsBlockReader(UfsManager ufsManager, UfsInputStreamCache ufsInStreamCache, BlockMeta blockMeta, long offset, UfsBlockReadOptions ufsBlockReadOptions, long pageSize)

Method Summary

Modifier and Type	Method and Description
void	close()
ReadableByteChannel	getChannel() Returns a readable byte channel of the block.
ReadableByteChannel	getChannel(long offset)
long	getLength() Gets the length of the block in bytes.
String	getLocation()
UfsBlockReadOptions	getUfsReadOptions()
boolean	isClosed()
ByteBuffer	read(long offset, long length) Reads data from the block.
int	readPageAtIndex(ByteBuffer buffer, long pageIndex) Reads a page from the UFS block at index pageIndex.
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

PagedUfsBlockReader

public PagedUfsBlockReader(UfsManager ufsManager,
                           UfsInputStreamCache ufsInStreamCache,
                           BlockMeta blockMeta,
                           long offset,
                           UfsBlockReadOptions ufsBlockReadOptions,
                           long pageSize)

Parameters:

ufsManager -

ufsInStreamCache -

blockMeta -

offset -

ufsBlockReadOptions -

pageSize -

Method Detail

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

readPageAtIndex

public int readPageAtIndex(ByteBuffer buffer,
                           long pageIndex)
                    throws IOException

Reads a page from the UFS block at index pageIndex. This method will try to read as many bytes as the page size designated by PropertyKey.USER_CLIENT_CACHE_PAGE_SIZE, and append to buffer. If pageIndex points to the last page of the block, the size of the data read can be smaller than the page size.

Parameters:

buffer - writable output buffer, must have enough remaining space for a page

pageIndex - the index of the page within the block

Returns:

number of bytes read, or -1 if end of block is reached

Throws:

IOException

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

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

getChannel

public ReadableByteChannel getChannel(long offset)

Parameters:

offset - offset within the block

Returns:

readable channel

getUfsReadOptions

public UfsBlockReadOptions getUfsReadOptions()

Returns:

ufs block read options which this read was created with

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

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

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