org.apache.lucene.facet.encoding

Class VInt8IntEncoder

java.lang.Object

org.apache.lucene.facet.encoding.IntEncoder

org.apache.lucene.facet.encoding.VInt8IntEncoder

public final class VInt8IntEncoder
extends IntEncoder

An IntEncoder which implements variable length encoding. A number is encoded as follows:

• If it is less than 127 and non-negative, i.e. uses only 7 bits, it is encoded as a single byte: 0bbbbbbb.
• If it occupies more than 7 bits, it is represented as a series of bytes, each byte carrying 7 bits. All but the last byte have the MSB set, the last one has it unset.

Example:

1. n = 117 = 01110101: This has less than 8 significant bits, therefore is encoded as 01110101 = 0x75.
2. n = 100000 = (binary) 11000011010100000. This has 17 significant bits, thus needs three Vint8 bytes. Pad it to a multiple of 7 bits, then split it into chunks of 7 and add an MSB, 0 for the last byte, 1 for the others: 1|0000110 1|0001101 0|0100000 = 0x86 0x8D 0x20.

NOTE: although this encoder is not limited to values ≥ 0, it is not recommended for use with negative values, as their encoding will result in 5 bytes written to the output stream, rather than 4. For such values, either use SimpleIntEncoder or write your own version of variable length encoding, which can better handle negative values.

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

Constructor Summary

Constructors

Constructor and Description
VInt8IntEncoder()

Method Summary

Methods

Modifier and Type	Method and Description
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 java.lang.Object

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

Constructor Detail

VInt8IntEncoder

public VInt8IntEncoder()

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