Package org.apache.hadoop.io.compress.lz4

Class Lz4Compressor

java.lang.Object

org.apache.hadoop.io.compress.lz4.Lz4Compressor

All Implemented Interfaces:

Compressor

public class Lz4Compressor
extends java.lang.Object
implements Compressor

A Compressor based on the lz4 compression algorithm. http://code.google.com/p/lz4/

Constructor Summary

Constructors

Constructor	Description
Lz4Compressor()	Creates a new compressor with the default buffer size.
Lz4Compressor(int directBufferSize)	Creates a new compressor.
Lz4Compressor(int directBufferSize, boolean useLz4HC)	Creates a new compressor.

Method Summary

Modifier and Type	Method	Description
int	compress(byte[] b, int off, int len)	Fills specified buffer with compressed data.
void	end()	Closes the compressor and discards any unprocessed input.
void	finish()	When called, indicates that compression should end with the current contents of the input buffer.
boolean	finished()	Returns true if the end of the compressed data output stream has been reached.
long	getBytesRead()	Return number of bytes given to this compressor since last reset.
long	getBytesWritten()	Return number of bytes consumed by callers of compress since last reset.
boolean	needsInput()	Returns true if the input data buffer is empty and #setInput() should be called to provide more input.
void	reinit(Configuration conf)	Prepare the compressor to be used in a new stream with settings defined in the given Configuration
void	reset()	Resets compressor so that a new set of input data can be processed.
void	setDictionary(byte[] b, int off, int len)	Does nothing.
void	setInput(byte[] b, int off, int len)	Sets input data for compression.

Methods inherited from class java.lang.Object

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

Constructor Detail

Lz4Compressor

public Lz4Compressor(int directBufferSize,
                     boolean useLz4HC)

Creates a new compressor.

Parameters:

directBufferSize - size of the direct buffer to be used.

useLz4HC - use high compression ratio version of lz4, which trades CPU for compression ratio.

Lz4Compressor

public Lz4Compressor(int directBufferSize)

Creates a new compressor.

Parameters:

directBufferSize - size of the direct buffer to be used.

Lz4Compressor

public Lz4Compressor()

Creates a new compressor with the default buffer size.

Method Detail

setInput

public void setInput(byte[] b,
                     int off,
                     int len)

Sets input data for compression. This should be called whenever #needsInput() returns true indicating that more input data is required.

Specified by:

setInput in interface Compressor

Parameters:

b - Input data

off - Start offset

len - Length

setDictionary

public void setDictionary(byte[] b,
                          int off,
                          int len)

Does nothing.

Specified by:

setDictionary in interface Compressor

Parameters:

b - Dictionary data bytes

off - Start offset

len - Length

needsInput

public boolean needsInput()

Returns true if the input data buffer is empty and #setInput() should be called to provide more input.

Specified by:

needsInput in interface Compressor

Returns:

true if the input data buffer is empty and #setInput() should be called in order to provide more input.

finish

public void finish()

When called, indicates that compression should end with the current contents of the input buffer.

Specified by:

finish in interface Compressor

finished

public boolean finished()

Returns true if the end of the compressed data output stream has been reached.

Specified by:

finished in interface Compressor

Returns:

true if the end of the compressed data output stream has been reached.

compress

public int compress(byte[] b,
                    int off,
                    int len)
             throws java.io.IOException

Fills specified buffer with compressed data. Returns actual number of bytes of compressed data. A return value of 0 indicates that needsInput() should be called in order to determine if more input data is required.

Specified by:

compress in interface Compressor

Parameters:

b - Buffer for the compressed data

off - Start offset of the data

len - Size of the buffer

Returns:

The actual number of bytes of compressed data.

Throws:

java.io.IOException - raised on errors performing I/O.

reset

public void reset()

Resets compressor so that a new set of input data can be processed.

Specified by:

reset in interface Compressor

reinit

public void reinit(Configuration conf)

Prepare the compressor to be used in a new stream with settings defined in the given Configuration

Specified by:

reinit in interface Compressor

Parameters:

conf - Configuration from which new setting are fetched

getBytesRead

public long getBytesRead()

Return number of bytes given to this compressor since last reset.

Specified by:

getBytesRead in interface Compressor

Returns:

bytes read.

getBytesWritten

public long getBytesWritten()

Return number of bytes consumed by callers of compress since last reset.

Specified by:

getBytesWritten in interface Compressor

Returns:

bytes written.

end

public void end()

Closes the compressor and discards any unprocessed input.

Specified by:

end in interface Compressor