MurmurHash.java

/* --------------------------------------------------------- *
 *    __________    D E L T A S C R I P T                    *
 *   (_________()                                            *
 *    /  ===   /   - A fast, dynamic scripting language      *
 *   |  ==    |    - Version 4.13.11.0                       *
 *   /  ===   /    - Developed by Adam R. Nelson             *
 *  |  =  =  |     - 2011-2013                               *
 *  /  ===   /     - Distributed under GNU LGPL v3           *
 * (________()     - http://github.com/ar-nelson/deltascript *
 *                                                           *
 * --------------------------------------------------------- */

package com.sector91.util;

/**
 * <p>Ported by Derek Young from the C version (specifically the endian-neutral
 * version) from:</p>
 * <p><a href="http://murmurhash.googlepages.com/">
 *     http://murmurhash.googlepages.com/
 * </a></p>
 *
 * <p>released to the public domain - dmy999@gmail.com</p>
 */
public class MurmurHash
{
    @SuppressWarnings("fallthrough")
    public static int hash(byte[] data, int seed)
    {
        // 'm' and 'r' are mixing constants generated offline.
        // They're not really 'magic', they just happen to work well.
        int m = 0x5bd1e995;
        int r = 24;

        // Initialize the hash to a 'random' value
        int len = data.length;
        int h = seed ^ len;

        int i = 0;
        while (len  >= 4)
        {
            int k = data[i + 0] & 0xFF;
            k |= (data[i + 1] & 0xFF) << 8;
            k |= (data[i + 2] & 0xFF) << 16;
            k |= (data[i + 3] & 0xFF) << 24;

            k *= m;
            k ^= k >>> r;
            k *= m;

            h *= m;
            h ^= k;

            i += 4;
            len -= 4;
        }

        switch (len) {
        case 3: h ^= (data[i + 2] & 0xFF) << 16;
        case 2: h ^= (data[i + 1] & 0xFF) << 8;
        case 1: h ^= (data[i + 0] & 0xFF);
                h *= m;
        }

        h ^= h >>> 13;
        h *= m;
        h ^= h >>> 15;

        return h;
    }
    
    public static int hash(String data)
    {return hash(data.getBytes(), 0x9747b28c);}
}