org.sindice.siren.index.codecs.block

Class VIntBlockCompressor

java.lang.Object

org.sindice.siren.index.codecs.block.BlockCompressor

org.sindice.siren.index.codecs.block.VIntBlockCompressor

public class VIntBlockCompressor
extends BlockCompressor

Implementation of the BlockCompressor based on the Variable Integer encoding algorithm.

Field Summary

Fields

Modifier and Type	Field and Description
protected int	HEADER_SIZE Size of header in buffer

Constructor Summary

Constructors

Constructor and Description
VIntBlockCompressor()

Method Summary

Methods

Modifier and Type	Method and Description
void	compress(org.apache.lucene.util.IntsRef input, org.apache.lucene.util.BytesRef output) Compress the uncompressed data into the buffer using variable integer encoding technique.
int	getWindowSize() Return the window size over the IntsRef input buffer used during compression.
int	maxCompressedSize(int arraySize) The maximum size in bytes of a compressed block of values

Methods inherited from class java.lang.Object

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

Field Detail

HEADER_SIZE

protected final int HEADER_SIZE

Size of header in buffer

See Also:

Constant Field Values

Constructor Detail

VIntBlockCompressor

public VIntBlockCompressor()

Method Detail

compress

public void compress(org.apache.lucene.util.IntsRef input,
            org.apache.lucene.util.BytesRef output)

Compress the uncompressed data into the buffer using variable integer encoding technique. All uncompressed integers are stored sequentially in compressed form in the buffer after the header.

No header is stored.

Specified by:

compress in class BlockCompressor

maxCompressedSize

public int maxCompressedSize(int arraySize)

Description copied from class: BlockCompressor

The maximum size in bytes of a compressed block of values

Specified by:

maxCompressedSize in class BlockCompressor

getWindowSize

public int getWindowSize()

Description copied from class: BlockCompressor

Return the window size over the IntsRef input buffer used during compression.

This is to avoid ArrayIndexOutOfBoundsException if the compressor is working on a buffer which size does not match a multiple of the window size.

For example, AForBlockCompressor is performing compression using a window of 32 integers. In the case of short postings list with 5 integers, the instantiated input buffer must be a multiple of window size, i.e., 32 in this case. If the postings list would contain 33 integers instead, then the instantiated input buffer should be 64.

Specified by:

getWindowSize in class BlockCompressor