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 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