Package me.lemire.integercompression

Class FastPFOR128

java.lang.Object

me.lemire.integercompression.FastPFOR128

All Implemented Interfaces:

IntegerCODEC, SkippableIntegerCODEC

public class FastPFOR128
extends Object
implements IntegerCODEC, SkippableIntegerCODEC

This class is similar to FastPFOR but uses a small block size. Note that this does not use differential coding: if you are working on sorted lists, you should first compute deltas, @see me.lemire.integercompression.differential.Delta#delta. For multi-threaded applications, each thread should use its own FastPFOR object.

Author:

Daniel Lemire

Field Summary

Fields

Modifier and Type	Field	Description
static final int	BLOCK_SIZE
static final int	DEFAULT_PAGE_SIZE

Constructor Summary

Constructors

Constructor	Description
FastPFOR128()	Construct the fastPFOR CODEC with default parameters.
FastPFOR128(int pagesize)	Construct the FastPFOR CODEC.

Method Summary

Modifier and Type	Method	Description
void	compress(int[] in, IntWrapper inpos, int inlength, int[] out, IntWrapper outpos)	Compress data from an array to another array.
void	headlessCompress(int[] in, IntWrapper inpos, int inlength, int[] out, IntWrapper outpos)	Compress data in blocks of BLOCK_SIZE integers (if fewer than BLOCK_SIZE integers are provided, nothing is done).
void	headlessUncompress(int[] in, IntWrapper inpos, int inlength, int[] out, IntWrapper outpos, int mynvalue)	Uncompress data in blocks of integers.
protected ByteBuffer	makeBuffer(int sizeInBytes)	Creates a new buffer of the requested size.
String	toString()
void	uncompress(int[] in, IntWrapper inpos, int inlength, int[] out, IntWrapper outpos)	Uncompress data from an array to another array.

Methods inherited from class java.lang.Object

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

Field Details

DEFAULT_PAGE_SIZE

public static final int DEFAULT_PAGE_SIZE

See Also:

• Constant Field Values

BLOCK_SIZE

public static final int BLOCK_SIZE

See Also:

• Constant Field Values

Constructor Details

FastPFOR128

public FastPFOR128(int pagesize)

Construct the FastPFOR CODEC.

Parameters:

pagesize - the desired page size (recommended value is FastPFOR.DEFAULT_PAGE_SIZE)

FastPFOR128

public FastPFOR128()

Construct the fastPFOR CODEC with default parameters.

Method Details

headlessCompress

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

Compress data in blocks of BLOCK_SIZE integers (if fewer than BLOCK_SIZE integers are provided, nothing is done).

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

See Also:

• IntegerCODEC.compress(int[], IntWrapper, int, int[], IntWrapper)

headlessUncompress

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

Uncompress data in blocks of integers. In this particular case, the inlength parameter is ignored: it is deduced from the compressed data.

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

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

See Also:

• IntegerCODEC.compress(int[], IntWrapper, int, int[], IntWrapper)

compress

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

Description copied from interface: IntegerCODEC

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.

Specified by:

compress in interface IntegerCODEC

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

uncompress

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

Description copied from interface: IntegerCODEC

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

Specified by:

uncompress in interface IntegerCODEC

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 compressed output

outpos - where to start writing the uncompressed output in out

toString

public String toString()

Overrides:

toString in class Object

makeBuffer

protected ByteBuffer makeBuffer(int sizeInBytes)

Creates a new buffer of the requested size. In case you need a different way to allocate buffers, you can override this method with a custom behavior. The default implementation allocates a new Java direct ByteBuffer on each invocation.

Parameters:

sizeInBytes -

Returns: