1 rizwank 1.1 /* Implements a string hashing function.
 2                Copyright (C) 1995, 1997 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 Library General Public
15                License along with the GNU C Library; see the file COPYING.LIB.  If not,
16                write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17                Boston, MA 02111-1307, USA.  */
18             
19             /* @@ end of prolog @@ */
20             
21             #ifndef PARAMS
22 rizwank 1.1 # if __STDC__
23             #  define PARAMS(Args) Args
24             # else
25             #  define PARAMS(Args) ()
26             # endif
27             #endif
28             
29             /* We assume to have `unsigned long int' value with at least 32 bits.  */
30             #define HASHWORDBITS 32
31             
32             
33             /* Defines the so called `hashpjw' function by P.J. Weinberger
34                [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools,
35                1986, 1987 Bell Telephone Laboratories, Inc.]  */
36             static unsigned long hash_string PARAMS ((const char *__str_param));
37             
38             static inline unsigned long
39             hash_string (str_param)
40                  const char *str_param;
41             {
42               unsigned long int hval, g;
43 rizwank 1.1   const char *str = str_param;
44             
45               /* Compute the hash value for the given string.  */
46               hval = 0;
47               while (*str != '\0')
48                 {
49                   hval <<= 4;
50                   hval += (unsigned long) *str++;
51                   g = hval & ((unsigned long) 0xf << (HASHWORDBITS - 4));
52                   if (g != 0)
53             	{
54             	  hval ^= g >> (HASHWORDBITS - 8);
55             	  hval ^= g;
56             	}
57                 }
58               return hval;
59             }