1*f7cc78ecSespie /* Implements a string hashing function.
2*f7cc78ecSespie Copyright (C) 1995, 1997 Free Software Foundation, Inc.
3*f7cc78ecSespie
4*f7cc78ecSespie This program is free software; you can redistribute it and/or modify
5*f7cc78ecSespie it under the terms of the GNU General Public License as published by
6*f7cc78ecSespie the Free Software Foundation; either version 2, or (at your option)
7*f7cc78ecSespie any later version.
8*f7cc78ecSespie
9*f7cc78ecSespie This program is distributed in the hope that it will be useful,
10*f7cc78ecSespie but WITHOUT ANY WARRANTY; without even the implied warranty of
11*f7cc78ecSespie MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12*f7cc78ecSespie GNU General Public License for more details.
13*f7cc78ecSespie
14*f7cc78ecSespie You should have received a copy of the GNU Library General Public
15*f7cc78ecSespie License along with the GNU C Library; see the file COPYING.LIB. If not,
16*f7cc78ecSespie write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17*f7cc78ecSespie Boston, MA 02111-1307, USA. */
18*f7cc78ecSespie
19*f7cc78ecSespie /* @@ end of prolog @@ */
20*f7cc78ecSespie
21*f7cc78ecSespie #ifndef PARAMS
22*f7cc78ecSespie # if __STDC__
23*f7cc78ecSespie # define PARAMS(Args) Args
24*f7cc78ecSespie # else
25*f7cc78ecSespie # define PARAMS(Args) ()
26*f7cc78ecSespie # endif
27*f7cc78ecSespie #endif
28*f7cc78ecSespie
29*f7cc78ecSespie /* We assume to have `unsigned long int' value with at least 32 bits. */
30*f7cc78ecSespie #define HASHWORDBITS 32
31*f7cc78ecSespie
32*f7cc78ecSespie
33*f7cc78ecSespie /* Defines the so called `hashpjw' function by P.J. Weinberger
34*f7cc78ecSespie [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools,
35*f7cc78ecSespie 1986, 1987 Bell Telephone Laboratories, Inc.] */
36*f7cc78ecSespie static unsigned long hash_string PARAMS ((const char *__str_param));
37*f7cc78ecSespie
38*f7cc78ecSespie static inline unsigned long
hash_string(str_param)39*f7cc78ecSespie hash_string (str_param)
40*f7cc78ecSespie const char *str_param;
41*f7cc78ecSespie {
42*f7cc78ecSespie unsigned long int hval, g;
43*f7cc78ecSespie const char *str = str_param;
44*f7cc78ecSespie
45*f7cc78ecSespie /* Compute the hash value for the given string. */
46*f7cc78ecSespie hval = 0;
47*f7cc78ecSespie while (*str != '\0')
48*f7cc78ecSespie {
49*f7cc78ecSespie hval <<= 4;
50*f7cc78ecSespie hval += (unsigned long) *str++;
51*f7cc78ecSespie g = hval & ((unsigned long) 0xf << (HASHWORDBITS - 4));
52*f7cc78ecSespie if (g != 0)
53*f7cc78ecSespie {
54*f7cc78ecSespie hval ^= g >> (HASHWORDBITS - 8);
55*f7cc78ecSespie hval ^= g;
56*f7cc78ecSespie }
57*f7cc78ecSespie }
58*f7cc78ecSespie return hval;
59*f7cc78ecSespie }
60