org.sindice.siren.index.codecs.block

Class BlockCompressor

java.lang.Object

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

Direct Known Subclasses:

AForBlockCompressor, VIntBlockCompressor

public abstract class BlockCompressor
extends Object

Abstraction over the block compression algorithm.

Constructor Summary

Constructors

Constructor and Description
BlockCompressor()

Method Summary

Methods

Modifier and Type	Method and Description
abstract void	compress(org.apache.lucene.util.IntsRef input, org.apache.lucene.util.BytesRef output) Compress the specified list of integers into a byte array.
abstract int	getWindowSize() Return the window size over the IntsRef input buffer used during compression.
abstract int	maxCompressedSize(int blockSize) 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

Constructor Detail

BlockCompressor

public BlockCompressor()

Method Detail

getWindowSize

public abstract int getWindowSize()

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.

compress

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

Compress the specified list of integers into a byte array.

maxCompressedSize

public abstract int maxCompressedSize(int blockSize)

The maximum size in bytes of a compressed block of values