org.h2.dev.util

Class AnsCompression

java.lang.Object

org.h2.dev.util.AnsCompression

public class AnsCompression
extends java.lang.Object

An ANS (Asymmetric Numeral Systems) compression tool. It uses the range variant.

Method Summary

Modifier and Type	Method and Description
static void	countFrequencies(int[] freq, byte[] data) Count the frequencies of codes in the data, and increment the target frequency table.
static byte[]	decode(int[] freq, byte[] data, int length) Decode the data.
static byte[]	encode(int[] freq, byte[] data) Encode the data.
static void	scaleFrequencies(int[] freq, int total) Scale the frequencies to a new total.

Methods inherited from class java.lang.Object

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

Method Detail

countFrequencies

public static void countFrequencies(int[] freq,
                                    byte[] data)

Count the frequencies of codes in the data, and increment the target frequency table.

Parameters:

freq - the target frequency table

data - the data

scaleFrequencies

public static void scaleFrequencies(int[] freq,
                                    int total)

Scale the frequencies to a new total. Frequencies of 0 are kept as 0; larger frequencies result in at least 1.

Parameters:

freq - the (source and target) frequency table

total - the target total (sum of all frequencies)

encode

public static byte[] encode(int[] freq,
                            byte[] data)

Encode the data.

Parameters:

freq - the frequency table (will be scaled)

data - the source data (uncompressed)

Returns:

the compressed data

decode

public static byte[] decode(int[] freq,
                            byte[] data,
                            int length)

Decode the data.

Parameters:

freq - the frequency table (will be scaled)

data - the compressed data

length - the target length

Returns:

the uncompressed result