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

Class FilePosition

java.lang.Object

org.apache.hadoop.fs.impl.prefetch.FilePosition

public final class FilePosition
extends java.lang.Object

Provides functionality related to tracking the position within a file. The file is accessed through an in memory buffer. The absolute position within the file is the sum of start offset of the buffer within the file and the relative offset of the current access location within the buffer. A file is made up of equal sized blocks. The last block may be of a smaller size. The size of a buffer associated with this file is typically the same as block size.

Constructor Summary

Constructors

Constructor	Description
FilePosition(long fileSize, int blockSize)	Constructs an instance of FilePosition.

Method Summary

Modifier and Type	Method	Description
long	absolute()	Gets the current absolute position within this file.
int	blockNumber()	Gets the id of the current block.
java.nio.ByteBuffer	buffer()
boolean	bufferFullyRead()	Determines whether the current buffer has been fully read.
long	bufferStartOffset()	Gets the start of the current block's absolute offset.
BufferData	data()
void	incrementBytesRead(int n)
void	invalidate()	Marks the current position as invalid.
boolean	isLastBlock()	Determines whether the current block is the last block in this file.
boolean	isValid()	Determines if the current position is valid.
boolean	isWithinCurrentBuffer(long pos)	Determines whether the given absolute position lies within the current buffer.
int	numBufferReads()
int	numBytesRead()
int	numSingleByteReads()
int	relative()	Gets the current position within this file relative to the start of the associated buffer.
boolean	setAbsolute(long pos)	If the given pos lies within the current buffer, updates the current position to the specified value and returns true; otherwise returns false without changing the position.
void	setData(BufferData bufferData, long startOffset, long readOffset)	Associates a buffer with this file.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

FilePosition

public FilePosition(long fileSize,
                    int blockSize)

Constructs an instance of FilePosition.

Parameters:

fileSize - size of the associated file.

blockSize - size of each block within the file.

Throws:

java.lang.IllegalArgumentException - if fileSize is negative.

java.lang.IllegalArgumentException - if blockSize is zero or negative.

Method Detail

setData

public void setData(BufferData bufferData,
                    long startOffset,
                    long readOffset)

Associates a buffer with this file.

Parameters:

bufferData - the buffer associated with this file.

startOffset - Start offset of the buffer relative to the start of a file.

readOffset - Offset where reading starts relative to the start of a file.

Throws:

java.lang.IllegalArgumentException - if bufferData is null.

java.lang.IllegalArgumentException - if startOffset is negative.

java.lang.IllegalArgumentException - if readOffset is negative.

java.lang.IllegalArgumentException - if readOffset is outside the range [startOffset, buffer end].

buffer

public java.nio.ByteBuffer buffer()

data

public BufferData data()

absolute

public long absolute()

Gets the current absolute position within this file.

Returns:

the current absolute position within this file.

setAbsolute

public boolean setAbsolute(long pos)

If the given pos lies within the current buffer, updates the current position to the specified value and returns true; otherwise returns false without changing the position.

Parameters:

pos - the absolute position to change the current position to if possible.

Returns:

true if the given current position was updated, false otherwise.

relative

public int relative()

Gets the current position within this file relative to the start of the associated buffer.

Returns:

the current position within this file relative to the start of the associated buffer.

isWithinCurrentBuffer

public boolean isWithinCurrentBuffer(long pos)

Determines whether the given absolute position lies within the current buffer.

Parameters:

pos - the position to check.

Returns:

true if the given absolute position lies within the current buffer, false otherwise.

blockNumber

public int blockNumber()

Gets the id of the current block.

Returns:

the id of the current block.

isLastBlock

public boolean isLastBlock()

Determines whether the current block is the last block in this file.

Returns:

true if the current block is the last block in this file, false otherwise.

isValid

public boolean isValid()

Determines if the current position is valid.

Returns:

true if the current position is valid, false otherwise.

invalidate

public void invalidate()

Marks the current position as invalid.

bufferStartOffset

public long bufferStartOffset()

Gets the start of the current block's absolute offset.

Returns:

the start of the current block's absolute offset.

bufferFullyRead

public boolean bufferFullyRead()

Determines whether the current buffer has been fully read.

Returns:

true if the current buffer has been fully read, false otherwise.

incrementBytesRead

public void incrementBytesRead(int n)

numBytesRead

public int numBytesRead()

numSingleByteReads

public int numSingleByteReads()

numBufferReads

public int numBufferReads()

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object