org.apache.lucene.facet.encoding
Class FourFlagsIntEncoder

java.lang.Object
  org.apache.lucene.facet.encoding.IntEncoder
      org.apache.lucene.facet.encoding.ChunksIntEncoder
          org.apache.lucene.facet.encoding.FourFlagsIntEncoder

Direct Known Subclasses:

NOnesIntEncoder

public class FourFlagsIntEncoder
extends ChunksIntEncoder

A ChunksIntEncoder which encodes values in chunks of 4. Every group starts with a single byte (called indicator) which represents 4 - 2 bit flags, where the values:

• 1, 2 or 3 mean the encoded value is '1', '2' or '3' respectively.
• 0 means the value is encoded using VInt8IntEncoder, and the encoded bytes follow the indicator.
  Since value 0 is illegal, and 1-3 are encoded in the indicator, the actual value that is encoded is value-4, which saves some more bits.

Encoding example:

• Original values: 6, 16, 5, 9, 7, 1, 11
• After sorting: 1, 5, 6, 7, 9, 11, 16
• D-Gap computing: 1, 4, 1, 1, 2, 5 (so far - done by DGapIntEncoder)
• Encoding: 1,0,1,1 as the first indicator, followed by 0 (4-4), than 2,0,0,0 as the second indicator, followed by 1 (5-4) encoded with.
• Binary encode: 01 | 01 | 00 | 01 00000000 00 | 00 | 00 | 10 00000001 (indicators are underlined).
  NOTE: the order of the values in the indicator is lsb ⇒ msb, which allows for more efficient decoding.

WARNING: This API is experimental and might change in incompatible ways in the next release.

Field Summary

Fields inherited from class org.apache.lucene.facet.encoding.ChunksIntEncoder

encodeQueue, indicator, ordinal

Constructor Summary

FourFlagsIntEncoder()

Method Summary

IntDecoder	createMatchingDecoder() Returns an IntDecoder which can decode the values that were encoded with this encoder.
void	encode(IntsRef values, BytesRef buf) Encodes the values to the given buffer.
String	toString()

Methods inherited from class org.apache.lucene.facet.encoding.ChunksIntEncoder

encodeChunk

Methods inherited from class java.lang.Object

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

Constructor Detail

FourFlagsIntEncoder

public FourFlagsIntEncoder()

Method Detail

encode

public void encode(IntsRef values,
                   BytesRef buf)

Description copied from class: IntEncoder

Encodes the values to the given buffer. Note that the buffer's offset and length are set to 0.

Specified by:

encode in class IntEncoder

createMatchingDecoder

public IntDecoder createMatchingDecoder()

Description copied from class: IntEncoder

Returns an IntDecoder which can decode the values that were encoded with this encoder.

Specified by:

createMatchingDecoder in class IntEncoder

toString

public String toString()

Overrides:

toString in class Object