Module me.lemire.integercompression

Package me.lemire.longcompression

Class LongBinaryPacking

java.lang.Object

me.lemire.longcompression.LongBinaryPacking

All Implemented Interfaces:

LongCODEC, SkippableLongCODEC

public final class LongBinaryPacking
extends Object
implements LongCODEC, SkippableLongCODEC

Scheme based on a commonly used idea: can be extremely fast. It encodes integers in blocks of 64 longs. For arrays containing an arbitrary number of longs, you should use it in conjunction with another CODEC:

LongCODEC ic = 
  new Composition(new LongBinaryPacking(), new LongVariableByte()).

Note that this does not use differential coding: if you are working on sorted lists, you must compute the deltas separately.

For details, please see BinaryPacking

Author:

Benoit Lacelle

Field Summary

Fields

Modifier and Type	Field	Description
static final int	BLOCK_SIZE

Constructor Summary

Constructors

Constructor	Description
LongBinaryPacking()

Method Summary

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

BLOCK_SIZE

public static final int BLOCK_SIZE

See Also:

• Constant Field Values

Constructor Details

LongBinaryPacking

public LongBinaryPacking()

Method Details

compress

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

Description copied from interface: LongCODEC

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 longs (inlength = 12) are compressed to 3 longs, 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 LongCODEC

Parameters:

in - input array

inpos - where to start reading in the array

inlength - how many longs to compress

out - output array

outpos - where to write in the output array

headlessCompress

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

Description copied from interface: SkippableLongCODEC

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 longs (inlength = 12) are compressed to 3 longs, 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:

headlessCompress in interface SkippableLongCODEC

Parameters:

in - input array

inpos - where to start reading in the array

inlength - how many longs to compress

out - output array

outpos - where to write in the output array

uncompress

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

Description copied from interface: LongCODEC

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 LongCODEC

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

headlessUncompress

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

Description copied from interface: SkippableLongCODEC

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 SkippableLongCODEC

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 longs we want to decode, the actual number of longs decoded can be less

maxHeadlessCompressedLength

public int maxHeadlessCompressedLength(IntWrapper compressedPositions,
 int inlength)

Description copied from interface: SkippableLongCODEC

Compute the maximum number of longs 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 SkippableLongCODEC.headlessCompress(long[], IntWrapper, int, long[], IntWrapper).

Specified by:

maxHeadlessCompressedLength in interface SkippableLongCODEC

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 longs to be compressed

Returns:

the maximum number of longs needed in the output array

toString

public String toString()

Overrides:

toString in class Object