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

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