org.h2.compress

类 CompressLZF

java.lang.Object

org.h2.compress.CompressLZF

所有已实现的接口:

Compressor

public final class CompressLZF
extends Object
implements Compressor

This class implements the LZF lossless data compression algorithm. LZF is a Lempel-Ziv variant with byte-aligned output, and optimized for speed.

Safety/Use Notes:

• Each instance should be used by a single thread only.
• The data buffers should be smaller than 1 GB.
• For performance reasons, safety checks on expansion are omitted.
• Invalid compressed data can cause an ArrayIndexOutOfBoundsException.

The LZF compressed format knows literal runs and back-references:

• Literal run: directly copy bytes from input to output.
• Back-reference: copy previous data to output stream, with specified offset from location and length. The length is at least 3 bytes.

The first byte of the compressed stream is the control byte. For literal runs, the highest three bits of the control byte are not set, the lower bits are the literal run length, and the next bytes are data to copy directly into the output. For back-references, the highest three bits of the control byte are the back-reference length. If all three bits are set, then the back-reference length is stored in the next byte. The lower bits of the control byte combined with the next byte form the offset for the back-reference.

字段概要

从接口继承的字段 org.h2.compress.Compressor

DEFLATE, LZF, NO

构造器概要

构造器

构造器和说明
CompressLZF()

方法概要

限定符和类型	方法和说明
int	compress(byte[] in, int inPos, int inLen, byte[] out, int outPos) Compress a number of bytes.
int	compress(ByteBuffer in, int inPos, byte[] out, int outPos) Compress a number of bytes.
void	expand(byte[] in, int inPos, int inLen, byte[] out, int outPos, int outLen) Expand a number of compressed bytes.
static void	expand(ByteBuffer in, ByteBuffer out) Expand a number of compressed bytes.
int	getAlgorithm() Get the compression algorithm type.
void	setOptions(String options) Set the compression options.

从类继承的方法 java.lang.Object

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

构造器详细资料

CompressLZF

public CompressLZF()

方法详细资料

setOptions

public void setOptions(String options)

从接口复制的说明: Compressor

Set the compression options. This may include settings for higher performance but less compression.

指定者:

setOptions 在接口中 Compressor

参数:

options - the options

compress

public int compress(byte[] in,
                    int inPos,
                    int inLen,
                    byte[] out,
                    int outPos)

从接口复制的说明: Compressor

Compress a number of bytes.

指定者:

compress 在接口中 Compressor

参数:

in - the input data

inPos - the offset at the input array

inLen - the number of bytes to compress

out - the output area

outPos - the offset at the output array

返回:

the end position

compress

public int compress(ByteBuffer in,
                    int inPos,
                    byte[] out,
                    int outPos)

Compress a number of bytes.

参数:

in - the input data

inPos - the offset at the input buffer

out - the output area

outPos - the offset at the output array

返回:

the end position

expand

public void expand(byte[] in,
                   int inPos,
                   int inLen,
                   byte[] out,
                   int outPos,
                   int outLen)

从接口复制的说明: Compressor

Expand a number of compressed bytes.

指定者:

expand 在接口中 Compressor

参数:

in - the compressed data

inPos - the offset at the input array

inLen - the number of bytes to read

out - the output area

outPos - the offset at the output array

outLen - the size of the uncompressed data

expand

public static void expand(ByteBuffer in,
                          ByteBuffer out)

Expand a number of compressed bytes.

参数:

in - the compressed data

out - the output area

getAlgorithm

public int getAlgorithm()

从接口复制的说明: Compressor

Get the compression algorithm type.

指定者:

getAlgorithm 在接口中 Compressor

返回:

the type