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.

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

### Field Summary

Fields
`static MurmurHash2` `INSTANCE`

### Method Summary

Methods
`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 java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, 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