Java Murmur Hash murmurhash2_64(final byte[] data, int length, int seed)

Description

murmur hash 2.0, The murmur hash is a relatively fast hash function from http://murmurhash.googlepages.com/ for platforms with efficient multiplication.

License

Mozilla Public License

Declaration

public static long murmurhash2_64(final byte[] data, int length, int seed) 

Method Source Code

//package com.java2s;
/*//from w  w w. j a v  a 2s .c  o  m
 * Copyright 2004-2014 H2 Group. Multiple-Licensed under the MPL 2.0,
 * and the EPL 1.0 (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */

public class Main {
    public static long murmurhash2_64(String text) {
        final byte[] bytes = text.getBytes();
        return murmurhash2_64(bytes, bytes.length, 0xe17a1465);
    }

    /**
     * murmur hash 2.0, The murmur hash is a relatively fast hash function from http://murmurhash.googlepages.com/ for
     * platforms with efficient multiplication.
     *
     * @author Viliam Holub
     */
    public static long murmurhash2_64(final byte[] data, int length, int seed) {
        final long m = 0xc6a4a7935bd1e995L;
        final int r = 47;
        long h = (seed & 0xffffffffl) ^ (length * m);
        int length8 = length / 8;
        for (int i = 0; i < length8; i++) {
            final int i8 = i * 8;
            long k = ((long) data[i8 + 0] & 0xff) //
                    + (((long) data[i8 + 1] & 0xff) << 8) //
                    + (((long) data[i8 + 2] & 0xff) << 16)//
                    + (((long) data[i8 + 3] & 0xff) << 24) //
                    + (((long) data[i8 + 4] & 0xff) << 32)//
                    + (((long) data[i8 + 5] & 0xff) << 40)//
                    + (((long) data[i8 + 6] & 0xff) << 48) //
                    + (((long) data[i8 + 7] & 0xff) << 56);
            k *= m;
            k ^= k >>> r;
            k *= m;
            h ^= k;
            h *= m;
        }
        switch (length % 8) {
        case 7:
            h ^= (long) (data[(length & ~7) + 6] & 0xff) << 48;
        case 6:
            h ^= (long) (data[(length & ~7) + 5] & 0xff) << 40;
        case 5:
            h ^= (long) (data[(length & ~7) + 4] & 0xff) << 32;
        case 4:
            h ^= (long) (data[(length & ~7) + 3] & 0xff) << 24;
        case 3:
            h ^= (long) (data[(length & ~7) + 2] & 0xff) << 16;
        case 2:
            h ^= (long) (data[(length & ~7) + 1] & 0xff) << 8;
        case 1:
            h ^= (long) (data[length & ~7] & 0xff);
            h *= m;
        }
        ;
        h ^= h >>> r;
        h *= m;
        h ^= h >>> r;
        return h;
    }
}

Related

1. murmur2(final byte[] data)
2. murmur2(int value, int salt)
3. murmur3fmix(int value)
4. murmurHash(byte[] data, int offset, int length)
5. murmurHash(int code)
6. murmurHash3(int k)
7. murmurHash3(int x)
8. murmurHash3(int x)
9. MurmurHash3_fmix(int k)