1 /* $OpenBSD: hash_func.c,v 1.11 2016/05/29 20:47:49 guenther Exp $ */
2
3 /*-
4 * Copyright (c) 1990, 1993
5 * The Regents of the University of California. All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Margo Seltzer.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 * 3. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #include <sys/types.h>
36
37 #include <db.h>
38
39 /* Chris Torek's hash function. */
40 u_int32_t
__default_hash(const void * key,size_t len)41 __default_hash(const void *key, size_t len)
42 {
43 u_int32_t h, loop;
44 u_int8_t *k;
45
46 #define HASH4a h = (h << 5) - h + *k++;
47 #define HASH4b h = (h << 5) + h + *k++;
48 #define HASH4 HASH4b
49
50 h = 0;
51 k = (u_int8_t *)key;
52 if (len > 0) {
53 loop = (len + 8 - 1) >> 3;
54
55 switch (len & (8 - 1)) {
56 case 0:
57 do { /* All fall throughs */
58 HASH4;
59 case 7:
60 HASH4;
61 case 6:
62 HASH4;
63 case 5:
64 HASH4;
65 case 4:
66 HASH4;
67 case 3:
68 HASH4;
69 case 2:
70 HASH4;
71 case 1:
72 HASH4;
73 } while (--loop);
74 }
75
76 }
77 return (h);
78 }
79