lib/hash-pjw.c

   1 /* hash-pjw.c -- compute a hash value from a NUL-terminated string.
   2    Copyright 2001 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 #if HAVE_CONFIG_H
  19 # include <config.h>
  20 #endif
  21
  22 #include "hash-pjw.h"
  23
  24 /* A hash function for NUL-terminated char* strings using
  25    the method described in Aho, Sethi, & Ullman, p 436. */
  26
  27 unsigned int
  28 hash_pjw (const void *x, unsigned int tablesize)
  29 {
  30   const char *s = x;
  31   unsigned int h = 0;
  32   unsigned int g;
  33
  34   while (*s != 0)
  35     {
  36       h = (h << 4) + *s++;
  37       if ((g = h & (unsigned int) 0xf0000000) != 0)
  38         h = (h ^ (g >> 24)) ^ g;
  39     }
  40
  41   return (h % tablesize);
  42 }