org.apache.lucene.util.hash

Class MurmurHash2

java.lang.Object

org.apache.lucene.util.hash.HashFunction

org.apache.lucene.util.hash.MurmurHash2

All Implemented Interfaces:

NamedSPILoader.NamedSPI

public 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.

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

Field Summary

Fields

Modifier and Type	Field and Description
static String	HASH_NAME

Constructor Summary

Constructors

Constructor and Description
MurmurHash2()

Method Summary

Methods

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.

Methods inherited from class org.apache.lucene.util.hash.HashFunction

availableHashFunctionNames, forName, getName, toString

Methods inherited from class java.lang.Object

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

Field Detail

HASH_NAME

public static final String HASH_NAME

See Also:

Constant Field Values

Constructor Detail

MurmurHash2

public MurmurHash2()

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