Hashing.java revision 6d562f688e350ade3c025bfb1c4c8cca9b3e2030 
1/*
2 * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25package sun.misc;
26
27import java.util.concurrent.ThreadLocalRandom;
28
29/**
30 * Hashing utilities.
31 *
32 * Little endian implementations of Murmur3 hashing.
33 */
34public class Hashing {
35
36    /**
37     * Static utility methods only.
38     */
39    private Hashing() {
40        throw new Error("No instances");
41    }
42
43    // Spread bits to regularize both segment and index locations,
44    // using variant of single-word Wang/Jenkins hash.
45    //
46    // Based on commit 1424a2a1a9fc53dc8b859a77c02c924.
47    public static int singleWordWangJenkinsHash(Object k) {
48        int h = k.hashCode();
49
50        h += (h <<  15) ^ 0xffffcd7d;
51        h ^= (h >>> 10);
52        h += (h <<   3);
53        h ^= (h >>>  6);
54        h += (h <<   2) + (h << 14);
55        return h ^ (h >>> 16);
56    }
57}
58