uk.ac.starlink.util

Class Compression

java.lang.Object

uk.ac.starlink.util.Compression

public abstract class Compression
extends Object

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

Author:

Mark Taylor (Starlink)

Field Summary

Fields

Modifier and Type	Field and Description
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

Modifier and Type	Method and Description
abstract InputStream	decompress(InputStream raw) Returns a stream which is a decompressed version of the input stream, according to this objects compression type.
static InputStream	decompressStatic(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.
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 InputStream decompress(InputStream raw)
                                throws 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:

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:

IllegalArgumentException - if magic.length<MAGIC_SIZE

decompressStatic

public static InputStream decompressStatic(InputStream raw)
                                    throws IOException

Returns a decompressed version of the given input stream.

Parameters:

raw - the raw input stream

Returns:

the decompressed version of raw

Throws:

IOException

toString

public String toString()

Returns the name of this compression type.

Overrides:

toString in class Object

Returns:

string representation