Package ca.cgjennings.algo.compression

Class AbstractCompressor

java.lang.Object

ca.cgjennings.algo.compression.AbstractCompressor

All Implemented Interfaces:

Compressor

Direct Known Subclasses:

BZip2Compressor, DeflateCompressor, GZIPCompressor, LZMACompressor

public abstract class AbstractCompressor
extends java.lang.Object
implements Compressor

An abstract base class for Compressor implementations. Concrete classes need only implement the following methods:
Compressor.compress(java.io.InputStream, java.io.OutputStream) and
Compressor.decompress(java.io.InputStream, java.io.OutputStream)

Since:

3.0

Author:

Chris Jennings

Constructor Summary

Constructors

Constructor	Description
AbstractCompressor()	Creates a compressor that defaults to the maximum compression level.
AbstractCompressor(int compressionLevel)	Creates a compressor with the requested compression level.

Method Summary

Modifier and Type	Method	Description
void	compress(java.io.File in, java.io.File out)	Compresses a file, writing the result to another file.
void	compress(java.io.File in, java.io.File out, ProgressListener li)	Compresses a file, writing the result to another file.
void	decompress(java.io.File in, java.io.File out)	Decompresses a file, writing the result to another file.
void	decompress(java.io.File in, java.io.File out, ProgressListener li)	Decompresses a file, writing the result to another file.
void	decompress(java.io.InputStream in, java.io.OutputStream out)	Reads compressed data from the input stream, decompresses it, and writes it to the output stream.
int	getCompressionLevel()	Returns the current compression level.
protected void	pumpStream(java.io.InputStream in, java.io.OutputStream out, boolean allowNIO)	This convenience method is provided for concrete subclasses to copy the content of one stream to another stream.
void	setCompressionLevel(int level)	Sets the compression level for future compression operations.
protected java.io.InputStream	wrap(java.io.InputStream src)	Wraps the provided input stream with a buffer if necessary.
protected java.io.OutputStream	wrap(java.io.OutputStream src)	Wraps the provided output stream with a buffer if necessary.

Methods inherited from class java.lang.Object

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

Methods inherited from interface ca.cgjennings.algo.compression.Compressor

compress, filter, filter

Constructor Detail

AbstractCompressor

public AbstractCompressor()

Creates a compressor that defaults to the maximum compression level.

AbstractCompressor

public AbstractCompressor(int compressionLevel)

Creates a compressor with the requested compression level.

Parameters:

compressionLevel - the compression level, from 0-9

Method Detail

decompress

public void decompress(java.io.InputStream in,
                       java.io.OutputStream out)
                throws java.io.IOException

Description copied from interface: Compressor

Reads compressed data from the input stream, decompresses it, and writes it to the output stream.

Specified by:

decompress in interface Compressor

Parameters:

in - the source of data to decompress

out - the sink for decompressed data

Throws:

java.io.IOException - if an error occurs during decompression

compress

public void compress(java.io.File in,
                     java.io.File out)
              throws java.io.IOException

Description copied from interface: Compressor

Compresses a file, writing the result to another file.

Specified by:

compress in interface Compressor

Parameters:

in - the file to compress

out - the destination

Throws:

java.io.IOException - if an error occurs

compress

public void compress(java.io.File in,
                     java.io.File out,
                     ProgressListener li)
              throws java.io.IOException

Description copied from interface: Compressor

Compresses a file, writing the result to another file.

Specified by:

compress in interface Compressor

Parameters:

in - the file to compress

out - the destination

li - a listener that will be updated with compression progress

Throws:

java.io.IOException - if an error occurs

decompress

public void decompress(java.io.File in,
                       java.io.File out)
                throws java.io.IOException

Description copied from interface: Compressor

Decompresses a file, writing the result to another file.

Specified by:

decompress in interface Compressor

Parameters:

in - the file to decompress

out - the destination

Throws:

java.io.IOException - if an error occurs

decompress

public void decompress(java.io.File in,
                       java.io.File out,
                       ProgressListener li)
                throws java.io.IOException

Description copied from interface: Compressor

Decompresses a file, writing the result to another file.

Specified by:

decompress in interface Compressor

Parameters:

in - the file to decompress

out - the destination

li - a listener that will be updated with the decompression progress

Throws:

java.io.IOException - if an error occurs

getCompressionLevel

public final int getCompressionLevel()

Description copied from interface: Compressor

Returns the current compression level.

Specified by:

getCompressionLevel in interface Compressor

Returns:

the current compression level, from 0 to 9 inclusive

setCompressionLevel

public final void setCompressionLevel(int level)

Description copied from interface: Compressor

Sets the compression level for future compression operations. The compression level is an integer between 0 and 9 inclusive that indicates whether the compressor should favour low resource requirements (such as CPU time and memory) or high compression ratios (9=maximum compression). For some implementations, this value may have no effect.

Each compressor has its own default compression level chosen to balance the amount of compression against the resources required to compress and/or decompress the data. Setting the compression level higher than its default may result in a sharp increase in resource use, particularly during compression.

Specified by:

setCompressionLevel in interface Compressor

Parameters:

level - the compression level from 0 to 9, with higher values suggesting that the algorithm should try harder to compress the data

pumpStream

protected void pumpStream(java.io.InputStream in,
                          java.io.OutputStream out,
                          boolean allowNIO)
                   throws java.io.IOException

This convenience method is provided for concrete subclasses to copy the content of one stream to another stream. A typical use case is to create a compression (decompression) stream filter on the output (input) stream and then use this method to complete the compression (decompression) process.

Parameters:

in - the source

out - the sink

allowNIO - if true, use NIO to accelerate stream copying

Throws:

java.io.IOException - if an I/O exception occurs during copying

wrap

protected java.io.InputStream wrap(java.io.InputStream src)

Wraps the provided input stream with a buffer if necessary.

Parameters:

src - the source stream

Returns:

the (possibly wrapped) source stream

wrap

protected java.io.OutputStream wrap(java.io.OutputStream src)

Wraps the provided output stream with a buffer if necessary.

Parameters:

src - the source stream

Returns:

the (possibly wrapped) source stream