Module me.lemire.integercompression

Package me.lemire.integercompression

Class SkippableComposition

java.lang.Object

me.lemire.integercompression.SkippableComposition

All Implemented Interfaces:

SkippableIntegerCODEC

public class SkippableComposition
extends Object
implements SkippableIntegerCODEC

Helper class to compose schemes.

Author:

Daniel Lemire

Constructor Summary

Constructors

Constructor	Description
SkippableComposition(SkippableIntegerCODEC f1, SkippableIntegerCODEC f2)	Compose a scheme from a first one (f1) and a second one (f2).

Method Summary

Modifier and Type	Method	Description
void	headlessCompress(int[] in, IntWrapper inpos, int inlength, int[] out, IntWrapper outpos)	Compress data from an array to another array.
void	headlessUncompress(int[] in, IntWrapper inpos, int inlength, int[] out, IntWrapper outpos, int num)	Uncompress data from an array to another array.
int	maxHeadlessCompressedLength(IntWrapper compressedPositions, int inlength)	Compute the maximum number of integers that might be required to store the compressed form of a given input array segment, without headers.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Details

SkippableComposition

public SkippableComposition(SkippableIntegerCODEC f1,
 SkippableIntegerCODEC f2)

Compose a scheme from a first one (f1) and a second one (f2). The first one is called first and then the second one tries to compress whatever remains from the first run. By convention, the first scheme should be such that if, during decoding, a 32-bit zero is first encountered, then there is no output.

Parameters:

f1 - first codec

f2 - second codec

Method Details

headlessCompress

public void headlessCompress(int[] in,
 IntWrapper inpos,
 int inlength,
 int[] out,
 IntWrapper outpos)

Description copied from interface: SkippableIntegerCODEC

Compress data from an array to another array. Both inpos and outpos are modified to represent how much data was read and written to. If 12 ints (inlength = 12) are compressed to 3 ints, then inpos will be incremented by 12 while outpos will be incremented by 3. We use IntWrapper to pass the values by reference. Implementation note: contrary to IntegerCODEC.compress(int[], me.lemire.integercompression.IntWrapper, int, int[], me.lemire.integercompression.IntWrapper), this may skip writing information about the number of encoded integers.

Specified by:

headlessCompress in interface SkippableIntegerCODEC

Parameters:

in - input array

inpos - where to start reading in the array

inlength - how many integers to compress

out - output array

outpos - where to write in the output array

headlessUncompress

public void headlessUncompress(int[] in,
 IntWrapper inpos,
 int inlength,
 int[] out,
 IntWrapper outpos,
 int num)

Description copied from interface: SkippableIntegerCODEC

Uncompress data from an array to another array. Both inpos and outpos parameters are modified to indicate new positions after read/write.

Specified by:

headlessUncompress in interface SkippableIntegerCODEC

Parameters:

in - array containing data in compressed form

inpos - where to start reading in the array

inlength - length of the compressed data (ignored by some schemes)

out - array where to write the uncompressed output

outpos - where to start writing the uncompressed output in out

num - number of integers we want to decode. May be less than the actual number of compressed integers

maxHeadlessCompressedLength

public int maxHeadlessCompressedLength(IntWrapper compressedPositions,
 int inlength)

Description copied from interface: SkippableIntegerCODEC

Compute the maximum number of integers that might be required to store the compressed form of a given input array segment, without headers.

This is useful to pre-allocate the output buffer before calling SkippableIntegerCODEC.headlessCompress(int[], IntWrapper, int, int[], IntWrapper).

Specified by:

maxHeadlessCompressedLength in interface SkippableIntegerCODEC

Parameters:

compressedPositions - since not all schemes compress every input integer, this parameter returns how many input integers will actually be compressed. This is useful when composing multiple schemes.

inlength - number of integers to be compressed

Returns:

the maximum number of integers needed in the output array

toString

public String toString()

Overrides:

toString in class Object