uk.ac.starlink.util
Class Compression

java.lang.Object
  uk.ac.starlink.util.Compression

public abstract class Compression
extends java.lang.Object

Characterises the compression status of a stream, and provides methods for decompressing it.

Field Summary

static Compression	BZIP2 A Compression object representing BZip2 compression.
static Compression	COMPRESS A Compression object representing Unix compress-type compression.
static Compression	GZIP A Compression object representing GZip compression.
static int	MAGIC_SIZE Number of bytes needed to determine compression type (magic number).
static Compression	NONE A Compression object representing no compression (or perhaps an unknown one).

Method Summary

abstract java.io.InputStream	decompress(java.io.InputStream raw) Returns a stream which is a decompressed version of the input stream, according to this objects compression type.
static java.io.InputStream	decompressStatic(java.io.InputStream raw) Returns a decompressed version of the given input stream.
static Compression	getCompression(byte[] magic) Returns a Compression object characterising the compression (if any) represented by a given magic number.
java.lang.String	toString() Returns the name of this compression type.

Methods inherited from class java.lang.Object

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

Field Detail

MAGIC_SIZE

public static final int MAGIC_SIZE

Number of bytes needed to determine compression type (magic number).

See Also:

Constant Field Values

NONE

public static final Compression NONE

A Compression object representing no compression (or perhaps an unknown one). The decompress method will return the raw input stream unchanged.

GZIP

public static final Compression GZIP

A Compression object representing GZip compression.

BZIP2

public static final Compression BZIP2

A Compression object representing BZip2 compression.

COMPRESS

public static final Compression COMPRESS

A Compression object representing Unix compress-type compression.

Method Detail

decompress

public abstract java.io.InputStream decompress(java.io.InputStream raw)
                                        throws java.io.IOException

Returns a stream which is a decompressed version of the input stream, according to this objects compression type.

Parameters:

raw - the raw input stream

Returns:

a stream giving the decompressed version of raw

Throws:

java.io.IOException

getCompression

public static Compression getCompression(byte[] magic)

Returns a Compression object characterising the compression (if any) represented by a given magic number.

Parameters:

magic - a buffer containing the first MAGIC_SIZE bytes of input of the stream to be characterised

Returns:

a Compression object of the type represented by magic

Throws:

java.lang.IllegalArgumentException - if magic.length<MAGIC_SIZE

decompressStatic

public static java.io.InputStream decompressStatic(java.io.InputStream raw)
                                            throws java.io.IOException

Returns a decompressed version of the given input stream.

Parameters:

raw - the raw input stream

Returns:

the decompressed version of raw

Throws:

java.io.IOException

toString

public java.lang.String toString()

Returns the name of this compression type.

Overrides:

toString in class java.lang.Object

Returns:

string representation