Package ca.cgjennings.algo.compression

Interface Compressor

All Known Implementing Classes:

AbstractCompressor, BZip2Compressor, DeflateCompressor, GZIPCompressor, LZMACompressor

public interface Compressor

A generic interface for simple compression and decompression of data streams using various compression algorithms. In addition to supporting the filtered stream model used in the Java I/O libraries, Compressors use a pipe-style model in which data is transformed as it copied through from an input stream to an output stream. This style is more convenient in many applications.

Since:

3.0

Author:

Chris Jennings

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	compress(java.io.InputStream in, java.io.OutputStream out)	Reads the data from the input stream, compresses it, and writes it to the output stream.
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.
java.io.InputStream	filter(java.io.InputStream in)	Returns an input stream that reads decompresses data from a stream of compressed data.
java.io.OutputStream	filter(java.io.OutputStream out)	Returns an output stream that compresses data as it writes it to an existing stream.
int	getCompressionLevel()	Returns the current compression level.
void	setCompressionLevel(int level)	Sets the compression level for future compression operations.

Method Detail

setCompressionLevel

void setCompressionLevel(int level)

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.

Parameters:

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

Throws:

java.lang.IllegalArgumentException - if the requested level is out of range

getCompressionLevel

int getCompressionLevel()

Returns the current compression level.

Returns:

the current compression level, from 0 to 9 inclusive

compress

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

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

Parameters:

in - the source for data to compress

out - the sink for compressed data

Throws:

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

decompress

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

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

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

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

Compresses a file, writing the result to another file.

Parameters:

in - the file to compress

out - the destination

Throws:

java.io.IOException - if an error occurs

compress

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

Compresses a file, writing the result to another file.

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

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

Decompresses a file, writing the result to another file.

Parameters:

in - the file to decompress

out - the destination

Throws:

java.io.IOException - if an error occurs

decompress

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

Decompresses a file, writing the result to another file.

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

filter

java.io.OutputStream filter(java.io.OutputStream out)
                     throws java.io.IOException

Returns an output stream that compresses data as it writes it to an existing stream.

Parameters:

out - the stream to write compressed data to

Returns:

a filter stream that will compress data and write it to out

Throws:

java.io.IOException - if an error occurs while creating the stream

filter

java.io.InputStream filter(java.io.InputStream in)
                    throws java.io.IOException

Returns an input stream that reads decompresses data from a stream of compressed data.

Parameters:

in - the stream to read compressed data from

Returns:

a filter stream that will decompress data from in as it is read from

Throws:

java.io.IOException - if an error occurs while creating the stream