Fri Nov 3 17:27:49 1995 Roland McGrath <roland@churchy.gnu.ai.mit.edu>
[glibc.git] / intl / hash-string.h
blobe846b507acf24ff48208135cc58428ac20032966
1 /* hash-string - Implements a string hashing function.
2 Copyright (C) 1995 Software Foundation, Inc.
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.
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.
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
16 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
18 #ifdef HAVE_VALUES_H
19 # include <values.h>
20 #endif
22 /* @@ end of prolog @@ */
24 #ifndef BITSPERBYTE
25 # define BITSPERBYTE 8
26 #endif
28 #ifndef LONGBITS
29 # define LONGBITS (sizeof (long) * BITSPERBYTE)
30 #endif /* LONGBITS */
32 /* Defines the so called `hashpjw' function by P.J. Weinberger
33 [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools,
34 1986, 1987 Bell Telephone Laboratories, Inc.] */
35 static inline unsigned long
36 hash_string (str_param)
37 const char *str_param;
39 unsigned long hval, g;
40 const char *str = str_param;
42 /* Compute the hash value for the given string. */
43 hval = 0;
44 while (*str != '\0')
46 hval <<= 4;
47 hval += (unsigned long) *str++;
48 g = hval & ((unsigned long) 0xf << (LONGBITS - 4));
49 if (g != 0)
51 hval ^= g >> (LONGBITS - 8);
52 hval ^= g;
55 return hval;