1/*-
2 * Copyright (c) 2014 Dag-Erling Smørgrav
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#include <sys/hash.h>
28#include <sys/endian.h>
29#include <sys/stdint.h>
30#include <sys/types.h>
31
32#define rol32(i32, n) ((i32) << (n) | (i32) >> (32 - (n)))
33
34/*
35 * $FreeBSD$
36 * Simple implementation of the Murmur3-32 hash function optimized for
37 * aligned sequences of 32-bit words.  If len is not a multiple of 4, it
38 * will be rounded down, droping trailer bytes.
39 */
40uint32_t
41murmur3_aligned_32(const void *data, size_t len, uint32_t seed)
42{
43	const uint32_t *data32;
44	uint32_t hash, k;
45	size_t res;
46
47	/* initialize */
48	len -= len % sizeof(*data32);
49	res = len;
50	data32 = data;
51	hash = seed;
52
53	/* iterate */
54	for (res = 0; res < len; res += sizeof(*data32), data32++) {
55		k = le32toh(*data32);
56		k *= 0xcc9e2d51;
57		k = rol32(k, 15);
58		k *= 0x1b873593;
59		hash ^= k;
60		hash = rol32(hash, 13);
61		hash *= 5;
62		hash += 0xe6546b64;
63	}
64
65	/* finalize */
66	hash ^= (uint32_t)len;
67	hash ^= hash >> 16;
68	hash *= 0x85ebca6b;
69	hash ^= hash >> 13;
70	hash *= 0xc2b2ae35;
71	hash ^= hash >> 16;
72	return (hash);
73}
74
75