org.apache.lucene.codecs.bloom

Class MurmurHash2

java.lang.Object

org.apache.lucene.codecs.bloom.HashFunction

org.apache.lucene.codecs.bloom.MurmurHash2

public final class MurmurHash2
extends HashFunction

This is a very fast, non-cryptographic hash suitable for general hash-based lookup. See http://murmurhash.googlepages.com/ for more details.

The C version of MurmurHash 2.0 found at that site was ported to Java by Andrzej Bialecki (ab at getopt org).

The code from getopt.org was adapted by Mark Harwood in the form here as one of a pluggable choice of hashing functions as the core function had to be adapted to work with BytesRefs with offsets and lengths rather than raw byte arrays.

Field Summary

Fields

Modifier and Type	Field and Description
static MurmurHash2	INSTANCE

Method Summary

Modifier and Type	Method and Description
static int	hash(byte[] data, int seed, int offset, int len)
int	hash(BytesRef br) Hashes the contents of the referenced bytes
static int	hash32(byte[] data, int offset, int len) Generates 32 bit hash from byte array with default seed value.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

INSTANCE

public static final MurmurHash2 INSTANCE

Method Detail

hash

public static int hash(byte[] data,
                       int seed,
                       int offset,
                       int len)

hash32

public static final int hash32(byte[] data,
                               int offset,
                               int len)

Generates 32 bit hash from byte array with default seed value.

Parameters:

data - byte array to hash

offset - the start position in the array to hash

len - length of the array elements to hash

Returns:

32 bit hash of the given array

hash

public final int hash(BytesRef br)

Description copied from class: HashFunction

Hashes the contents of the referenced bytes

Specified by:

hash in class HashFunction

Parameters:

br - the data to be hashed

Returns:

the hash of the bytes referenced by bytes.offset and length bytes.length

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object