1 /* $OpenBSD: hash_func.c,v 1.1 2008/06/21 15:39:15 joris 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 #include <sys/queue.h>
37
38 #include "hash.h"
39
40 /* Chris Torek's hash function. */
41 u_int32_t
hash4(const char * key,size_t len)42 hash4(const char *key, size_t len)
43 {
44 u_int32_t h, loop;
45 const char *k;
46
47 #define HASH4 h = (h << 5) + h + *k++;
48
49 h = 0;
50 k = key;
51 if (len > 0) {
52 loop = (len + 8 - 1) >> 3;
53
54 switch (len & (8 - 1)) {
55 case 0:
56 do { /* All fall throughs */
57 HASH4;
58 case 7:
59 HASH4;
60 case 6:
61 HASH4;
62 case 5:
63 HASH4;
64 case 4:
65 HASH4;
66 case 3:
67 HASH4;
68 case 2:
69 HASH4;
70 case 1:
71 HASH4;
72 } while (--loop);
73 }
74
75 }
76 return (h);
77 }
78