Java Hash Calculate hashJenkins(int init, Object... vals)

Description

hash Jenkins

License

Open Source License

Declaration

public static int hashJenkins(int init, Object... vals) 

Method Source Code

//package com.java2s;
/*//from   w ww  . jav a  2s. c  o  m
 * Copyright (C) 2012-2013 University of Freiburg
 *
 * This file is part of SMTInterpol.
 *
 * SMTInterpol is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * SMTInterpol is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with SMTInterpol.  If not, see <http://www.gnu.org/licenses/>.
 */

public class Main {
    private final static int BASE = 0xdeadbeef;

    public static int hashJenkins(int init, Object... vals) {
        if (vals == null || vals.length == 0) {
            return init;
        }
        int a, b, c;
        a = b = c = BASE + (vals.length << 2) + init;
        int pos = 0;
        while (vals.length - pos > 3) {
            a += vals[pos].hashCode();
            b += vals[pos + 1].hashCode();
            c += vals[pos + 2].hashCode();
            // This is the mix function of Jenkins hash.
            // Note that we need >>> for unsigned shift.
            // rot(c,4) is ((c << 4) | (c >>> 28)).
            a -= c;
            a ^= ((c << 4) | (c >>> 28));
            c += b;
            b -= a;
            b ^= ((a << 6) | (a >>> 26));
            a += c;
            c -= b;
            c ^= ((b << 8) | (b >>> 24));
            b += a;
            a -= c;
            a ^= ((c << 16) | (c >>> 16));
            c += b;
            b -= a;
            b ^= ((a << 19) | (a >>> 13));
            a += c;
            c -= b;
            c ^= ((b << 4) | (b >>> 28));
            b += a;
            pos += 3;
        }
        switch (vals.length - pos) {
        case 3:
            c += vals[pos++].hashCode();
            // fallthrough
        case 2:
            b += vals[pos++].hashCode();
            // fallthrough
        case 1:
            a += vals[pos].hashCode();
            // This is the final mix function of Jenkins hash.
            c ^= b;
            c -= ((b << 14) | (b >>> 18));
            a ^= c;
            a -= ((c << 11) | (c >>> 21));
            b ^= a;
            b -= ((a << 25) | (a >>> 7));
            c ^= b;
            c -= ((b << 16) | (b >>> 16));
            a ^= c;
            a -= ((c << 4) | (c >>> 28));
            b ^= a;
            b -= ((a << 14) | (a >>> 18));
            c ^= b;
            c -= ((b << 24) | (b >>> 8));
            // fallthrough
        case 0:
            // fallthrough
        default:
            break;
        }
        return c;
    }

    public static int hashJenkins(int init, Object val) {
        int a, b, c;
        a = b = BASE + 4 + init;
        // slightly optimized version of hashJenkins(init, new Object[] {val})
        a += val.hashCode();
        c = -((b << 14) | (b >>> 18));
        a ^= c;
        a -= ((c << 11) | (c >>> 21));
        b ^= a;
        b -= ((a << 25) | (a >>> 7));
        c ^= b;
        c -= ((b << 16) | (b >>> 16));
        a ^= c;
        a -= ((c << 4) | (c >>> 28));
        b ^= a;
        b -= ((a << 14) | (a >>> 18));
        c ^= b;
        c -= ((b << 24) | (b >>> 8));
        return c;
    }
}

Related

1. hashInt(final int v)
2. hashIntArray(int seed, int[] data, int offset, int len)
3. hashIt(Object o)
4. hashJava32(byte[] byteList)
5. hashJava64(byte[] byteList)
6. hashLong(long id)
7. hashLong(long l)
8. hashMapCapacity(final int nElements)
9. hashMore(final int hash, final int more)