Package org.apache.hadoop.fs.impl.prefetch

Class BufferData

java.lang.Object

org.apache.hadoop.fs.impl.prefetch.BufferData

public final class BufferData
extends java.lang.Object

Holds the state of a ByteBuffer that is in use by CachingBlockManager. This class is not meant to be of general use. It exists into its own file due to its size. We use the term block and buffer interchangeably in this file because one buffer holds exactly one block of data. Holding all of the state associated with a block allows us to validate and control state transitions in a synchronized fashion.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	BufferData.State

Constructor Summary

Constructors

Constructor	Description
BufferData(int blockNumber, java.nio.ByteBuffer buffer)	Constructs an instances of this class.

Method Summary

Modifier and Type	Method	Description
java.util.concurrent.Future<java.lang.Void>	getActionFuture()
int	getBlockNumber()	Gets the id of this block.
java.nio.ByteBuffer	getBuffer()	Gets the buffer associated with this block.
long	getChecksum()	Gets the checksum of data in this block.
static long	getChecksum(java.nio.ByteBuffer buffer)	Computes CRC32 checksum of the given buffer's contents.
BufferData.State	getState()	Gets the state of this block.
void	setCaching(java.util.concurrent.Future<java.lang.Void> actionFuture)	Indicates that a caching operation is in progress.
void	setDone()	Indicates that this block is no longer of use and can be reclaimed.
void	setPrefetch(java.util.concurrent.Future<java.lang.Void> actionFuture)	Indicates that a prefetch operation is in progress.
void	setReady(BufferData.State... expectedCurrentState)	Marks the completion of reading data into the buffer.
boolean	stateEqualsOneOf(BufferData.State... states)
void	throwIfStateIncorrect(BufferData.State... states)	Helper that asserts the current state is one of the expected values.
java.lang.String	toString()
void	updateState(BufferData.State newState, BufferData.State... expectedCurrentState)	Updates the current state to the specified value.

Methods inherited from class java.lang.Object

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

Constructor Detail

BufferData

public BufferData(int blockNumber,
                  java.nio.ByteBuffer buffer)

Constructs an instances of this class.

Parameters:

blockNumber - Number of the block associated with this buffer.

buffer - The buffer associated with this block.

Throws:

java.lang.IllegalArgumentException - if blockNumber is negative.

java.lang.IllegalArgumentException - if buffer is null.

Method Detail

getBlockNumber

public int getBlockNumber()

Gets the id of this block.

Returns:

the id of this block.

getBuffer

public java.nio.ByteBuffer getBuffer()

Gets the buffer associated with this block.

Returns:

the buffer associated with this block.

getState

public BufferData.State getState()

Gets the state of this block.

Returns:

the state of this block.

getChecksum

public long getChecksum()

Gets the checksum of data in this block.

Returns:

the checksum of data in this block.

getChecksum

public static long getChecksum(java.nio.ByteBuffer buffer)

Computes CRC32 checksum of the given buffer's contents.

Parameters:

buffer - the buffer whose content's checksum is to be computed.

Returns:

the computed checksum.

getActionFuture

public java.util.concurrent.Future<java.lang.Void> getActionFuture()

setPrefetch

public void setPrefetch(java.util.concurrent.Future<java.lang.Void> actionFuture)

Indicates that a prefetch operation is in progress.

Parameters:

actionFuture - the Future of a prefetch action.

Throws:

java.lang.IllegalArgumentException - if actionFuture is null.

setCaching

public void setCaching(java.util.concurrent.Future<java.lang.Void> actionFuture)

Indicates that a caching operation is in progress.

Parameters:

actionFuture - the Future of a caching action.

Throws:

java.lang.IllegalArgumentException - if actionFuture is null.

setReady

public void setReady(BufferData.State... expectedCurrentState)

Marks the completion of reading data into the buffer. The buffer cannot be modified once in this state.

Parameters:

expectedCurrentState - the collection of states from which transition to READY is allowed.

setDone

public void setDone()

Indicates that this block is no longer of use and can be reclaimed.

updateState

public void updateState(BufferData.State newState,
                        BufferData.State... expectedCurrentState)

Updates the current state to the specified value. Asserts that the current state is as expected.

Parameters:

newState - the state to transition to.

expectedCurrentState - the collection of states from which transition to newState is allowed.

Throws:

java.lang.IllegalArgumentException - if newState is null.

java.lang.IllegalArgumentException - if expectedCurrentState is null.

throwIfStateIncorrect

public void throwIfStateIncorrect(BufferData.State... states)

Helper that asserts the current state is one of the expected values.

Parameters:

states - the collection of allowed states.

Throws:

java.lang.IllegalArgumentException - if states is null.

stateEqualsOneOf

public boolean stateEqualsOneOf(BufferData.State... states)

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object