1 /* hash-pjw.c -- compute a hash value from a NUL-terminated string. 2 3 Copyright (C) 2001, 2003, 2006, 2009-2020 Free Software Foundation, Inc. 4 5 This program is free software: you can redistribute it and/or modify 6 it under the terms of the GNU General Public License as published by 7 the Free Software Foundation; either version 3 of the License, or 8 (at your option) any later version. 9 10 This program is distributed in the hope that it will be useful, 11 but WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 13 GNU General Public License for more details. 14 15 You should have received a copy of the GNU General Public License 16 along with this program. If not, see <https://www.gnu.org/licenses/>. */ 17 18 #include <config.h> 19 20 #include "hash-pjw.h" 21 22 #include <limits.h> 23 24 #define SIZE_BITS (sizeof (size_t) * CHAR_BIT) 25 26 /* A hash function for NUL-terminated char* strings using 27 the method described by Bruno Haible. 28 See https://www.haible.de/bruno/hashfunc.html. */ 29 30 size_t hash_pjw(const void * x,size_t tablesize)31hash_pjw (const void *x, size_t tablesize) 32 { 33 const char *s; 34 size_t h = 0; 35 36 for (s = x; *s; s++) 37 h = *s + ((h << 9) | (h >> (SIZE_BITS - 9))); 38 39 return h % tablesize; 40 } 41