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1 /* Description of GNU message catalog format: string hashing function.
2    Copyright (C) 1995, 1997-1998, 2000-2003 Free Software Foundation, Inc.
3 
4    This program is free software; you can redistribute it and/or modify it
5    under the terms of the GNU Library General Public License as published
6    by 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 GNU
12    Library General Public License for more details.
13 
14    You should have received a copy of the GNU Library General Public
15    License along with this program; if not, write to the Free Software
16    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
17    USA.  */
18 
19 /* @@ end of prolog @@ */
20 
21 /* We assume to have `unsigned long int' value with at least 32 bits.  */
22 #define HASHWORDBITS 32
23 
24 
25 /* Defines the so called `hashpjw' function by P.J. Weinberger
26    [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools,
27    1986, 1987 Bell Telephone Laboratories, Inc.]  */
28 static inline unsigned long int
hash_string(const char * str_param)29 hash_string (const char *str_param)
30 {
31   unsigned long int hval, g;
32   const char *str = str_param;
33 
34   /* Compute the hash value for the given string.  */
35   hval = 0;
36   while (*str != '\0')
37     {
38       hval <<= 4;
39       hval += (unsigned char) *str++;
40       g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4));
41       if (g != 0)
42 	{
43 	  hval ^= g >> (HASHWORDBITS - 8);
44 	  hval ^= g;
45 	}
46     }
47   return hval;
48 }
49