org.h2.tools

Class CompressTool

java.lang.Object

org.h2.tools.CompressTool

public class CompressTool
extends java.lang.Object

A tool to losslessly compress data, and expand the compressed data again.

Method Summary

Modifier and Type	Method and Description
byte[]	compress(byte[] in, java.lang.String algorithm) Compressed the data using the specified algorithm.
byte[]	expand(byte[] in) Expands the compressed data.
static void	expand(byte[] in, byte[] out, int outPos) INTERNAL
static int	getCompressAlgorithm(java.lang.String algorithm) INTERNAL
static CompressTool	getInstance() Get a new instance.
static int	getVariableIntLength(int x) Get a variable size integer length using Rice coding.
static int	readVariableInt(byte[] buff, int pos) Read a variable size integer using Rice coding.
static java.io.InputStream	wrapInputStream(java.io.InputStream in, java.lang.String compressionAlgorithm, java.lang.String entryName) INTERNAL
static java.io.OutputStream	wrapOutputStream(java.io.OutputStream out, java.lang.String compressionAlgorithm, java.lang.String entryName) INTERNAL
static int	writeVariableInt(byte[] buff, int pos, int x) Write a variable size integer using Rice coding.

Methods inherited from class java.lang.Object

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

Method Detail

getInstance

public static CompressTool getInstance()

Get a new instance. Each instance uses a separate buffer, so multiple instances can be used concurrently. However each instance alone is not multithreading safe.

Returns:

a new instance

compress

public byte[] compress(byte[] in,
                       java.lang.String algorithm)

Compressed the data using the specified algorithm. If no algorithm is supplied, LZF is used

Parameters:

in - the byte array with the original data

algorithm - the algorithm (LZF, DEFLATE)

Returns:

the compressed data

expand

public byte[] expand(byte[] in)

Expands the compressed data.

Parameters:

in - the byte array with the compressed data

Returns:

the uncompressed data

expand

public static void expand(byte[] in,
                          byte[] out,
                          int outPos)

INTERNAL

readVariableInt

public static int readVariableInt(byte[] buff,
                                  int pos)

Read a variable size integer using Rice coding.

Parameters:

buff - the buffer

pos - the position

Returns:

the integer

writeVariableInt

public static int writeVariableInt(byte[] buff,
                                   int pos,
                                   int x)

Write a variable size integer using Rice coding. Negative values need 5 bytes.

Parameters:

buff - the buffer

pos - the position

x - the value

Returns:

the number of bytes written (0-5)

getVariableIntLength

public static int getVariableIntLength(int x)

Get a variable size integer length using Rice coding. Negative values need 5 bytes.

Parameters:

x - the value

Returns:

the number of bytes needed (0-5)

getCompressAlgorithm

public static int getCompressAlgorithm(java.lang.String algorithm)

INTERNAL

wrapOutputStream

public static java.io.OutputStream wrapOutputStream(java.io.OutputStream out,
                                                    java.lang.String compressionAlgorithm,
                                                    java.lang.String entryName)

INTERNAL

wrapInputStream

public static java.io.InputStream wrapInputStream(java.io.InputStream in,
                                                  java.lang.String compressionAlgorithm,
                                                  java.lang.String entryName)

INTERNAL