Package org.apache.hadoop.io.compress.bzip2

Class Bzip2Compressor

java.lang.Object

org.apache.hadoop.io.compress.bzip2.Bzip2Compressor

All Implemented Interfaces:

Compressor

public class Bzip2Compressor
extends java.lang.Object
implements Compressor

A Compressor based on the popular bzip2 compression algorithm. http://www.bzip2.org/

Constructor Summary

Constructors

Constructor	Description
Bzip2Compressor()	Creates a new compressor with a default values for the compression block size and work factor.
Bzip2Compressor(int blockSize, int workFactor, int directBufferSize)	Creates a new compressor using the specified block size.
Bzip2Compressor(Configuration conf)	Creates a new compressor, taking settings from the configuration.

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()	Returns the total number of uncompressed bytes input so far.
long	getBytesWritten()	Returns the total number of compressed bytes output so far.
static java.lang.String	getLibraryName()
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)	Sets preset dictionary for compression.
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

Bzip2Compressor

public Bzip2Compressor()

Creates a new compressor with a default values for the compression block size and work factor. Compressed data will be generated in bzip2 format.

Bzip2Compressor

public Bzip2Compressor(Configuration conf)

Creates a new compressor, taking settings from the configuration.

Parameters:

conf - configuration.

Bzip2Compressor

public Bzip2Compressor(int blockSize,
                       int workFactor,
                       int directBufferSize)

Creates a new compressor using the specified block size. Compressed data will be generated in bzip2 format.

Parameters:

blockSize - The block size to be used for compression. This is an integer from 1 through 9, which is multiplied by 100,000 to obtain the actual block size in bytes.

workFactor - This parameter is a threshold that determines when a fallback algorithm is used for pathological data. It ranges from 0 to 250.

directBufferSize - Size of the direct buffer to be used.

Method Detail

reinit

public void reinit(Configuration conf)

Prepare the compressor to be used in a new stream with settings defined in the given Configuration. It will reset the compressor's block size and and work factor.

Specified by:

reinit in interface Compressor

Parameters:

conf - Configuration storing new settings

setInput

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

Description copied from interface: Compressor

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)

Description copied from interface: Compressor

Sets preset dictionary for compression. A preset dictionary is used when the history buffer can be predetermined.

Specified by:

setDictionary in interface Compressor

Parameters:

b - Dictionary data bytes

off - Start offset

len - Length

needsInput

public boolean needsInput()

Description copied from interface: Compressor

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()

Description copied from interface: Compressor

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()

Description copied from interface: Compressor

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

Description copied from interface: Compressor

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.

getBytesWritten

public long getBytesWritten()

Returns the total number of compressed bytes output so far.

Specified by:

getBytesWritten in interface Compressor

Returns:

the total (non-negative) number of compressed bytes output so far

getBytesRead

public long getBytesRead()

Returns the total number of uncompressed bytes input so far.

Specified by:

getBytesRead in interface Compressor

Returns:

the total (non-negative) number of uncompressed bytes input so far

reset

public void reset()

Description copied from interface: Compressor

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

Specified by:

reset in interface Compressor

end

public void end()

Description copied from interface: Compressor

Closes the compressor and discards any unprocessed input.

Specified by:

end in interface Compressor

getLibraryName

public static java.lang.String getLibraryName()