org.apache.cassandra.utils

Class MurmurHash

java.lang.Object

org.apache.cassandra.utils.MurmurHash

public class MurmurHash
extends java.lang.Object

This is a very fast, non-cryptographic hash suitable for general hash-based lookup. See http://murmurhash.googlepages.com/ for more details. hash32() and hash64() are MurmurHash 2.0. hash3_x64_128() is *almost* MurmurHash 3.0. It was supposed to match, but we didn't catch a sign bug with the result that it doesn't. Unfortunately, we can't change it now without breaking Murmur3Partitioner. *

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

Constructor Summary

Constructors

Constructor and Description
MurmurHash()

Method Summary

Modifier and Type	Method and Description
protected static long	fmix(long k)
protected static long	getBlock(java.nio.ByteBuffer key, int offset, int index)
static long	hash2_64(java.nio.ByteBuffer key, int offset, int length, long seed)
static void	hash3_x64_128(java.nio.ByteBuffer key, int offset, int length, long seed, long[] result)
static int	hash32(java.nio.ByteBuffer data, int offset, int length, int seed)
static long[]	inv_hash3_x64_128(long[] result)
protected static long	invFmix(long k)
protected static long	invRotl64(long v, int n)
protected static long	invRShiftXor(long value, int shift)
static long	invTailReverse(long num) This gives a correct reversal of the tail byte flip which is needed if want a non mod16==0 byte hash inv or to target a hash for a given schema.
protected static long	rotl64(long v, int n)

Methods inherited from class java.lang.Object

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

Constructor Detail

MurmurHash

public MurmurHash()

Method Detail

hash32

public static int hash32(java.nio.ByteBuffer data,
                         int offset,
                         int length,
                         int seed)

hash2_64

public static long hash2_64(java.nio.ByteBuffer key,
                            int offset,
                            int length,
                            long seed)

getBlock

protected static long getBlock(java.nio.ByteBuffer key,
                               int offset,
                               int index)

rotl64

protected static long rotl64(long v,
                             int n)

fmix

protected static long fmix(long k)

hash3_x64_128

public static void hash3_x64_128(java.nio.ByteBuffer key,
                                 int offset,
                                 int length,
                                 long seed,
                                 long[] result)

invRotl64

protected static long invRotl64(long v,
                                int n)

invRShiftXor

protected static long invRShiftXor(long value,
                                   int shift)

invFmix

protected static long invFmix(long k)

invTailReverse

public static long invTailReverse(long num)

This gives a correct reversal of the tail byte flip which is needed if want a non mod16==0 byte hash inv or to target a hash for a given schema.

inv_hash3_x64_128

public static long[] inv_hash3_x64_128(long[] result)