1 /*-
2 * Copyright (c) 2013, Joseph Koshy
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 * in this position and unchanged.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27 /*
28 * An implementation of the Fowler-Noll-Vo hash function.
29 *
30 * References:
31 * - http://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
32 * - http://www.isthe.com/chongo/tech/comp/fnv/
33 */
34
35 #include <sys/types.h>
36
37 #include <limits.h>
38
39 #include "_libelftc.h"
40
41 ELFTC_VCSID("$Id: libelftc_hash.c 2870 2013-01-07 10:38:43Z jkoshy $");
42
43 /*
44 * Use the size of an 'int' to determine the magic numbers used by the
45 * hash function.
46 */
47
48 #if INT_MAX == 2147483647UL
49 #define FNV_PRIME 16777619UL
50 #define FNV_OFFSET 2166136261UL
51 #elif INT_MAX == 18446744073709551615ULL
52 #define FNV_PRIME 1099511628211ULL
53 #define FNV_OFFSET 14695981039346656037ULL
54 #else
55 #error sizeof(int) is unknown.
56 #endif
57
58 unsigned int
libelftc_hash_string(const char * s)59 libelftc_hash_string(const char *s)
60 {
61 char c;
62 unsigned int hash;
63
64 for (hash = FNV_OFFSET; (c = *s) != '\0'; s++) {
65 hash ^= c;
66 hash *= FNV_PRIME;
67 }
68
69 return (hash);
70 }
71