/* hash-pjw.c -- compute a hash value from a NUL-terminated string.
- Copyright 2001, 2003 Free Software Foundation, Inc.
- This program is free software; you can redistribute it and/or modify
+ Copyright (C) 2001, 2003, 2006, 2009-2011 Free Software Foundation, Inc.
+
+ This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 2, or (at your option)
- any later version.
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
- along with this program; if not, write to the Free Software Foundation,
- Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
-#if HAVE_CONFIG_H
-# include <config.h>
-#endif
+#include <config.h>
#include "hash-pjw.h"
+#include <limits.h>
+
+#define SIZE_BITS (sizeof (size_t) * CHAR_BIT)
+
/* A hash function for NUL-terminated char* strings using
- the method described in Aho, Sethi, & Ullman, p 436.
- Note that this hash function produces a lot of collisions when used
- with short strings with very varied bit patterns.
+ the method described by Bruno Haible.
See http://www.haible.de/bruno/hashfunc.html. */
-unsigned int
-hash_pjw (const void *x, unsigned int tablesize)
+size_t
+hash_pjw (const void *x, size_t tablesize)
{
- const char *s = x;
- unsigned int h = 0;
- unsigned int g;
-
- while (*s != 0)
- {
- h = (h << 4) + *s++;
- if ((g = h & (unsigned int) 0xf0000000) != 0)
- h = (h ^ (g >> 24)) ^ g;
- }
-
- return (h % tablesize);
+ const char *s;
+ size_t h = 0;
+
+ for (s = x; *s; s++)
+ h = *s + ((h << 9) | (h >> (SIZE_BITS - 9)));
+
+ return h % tablesize;
}