1 /* $NetBSD: hash-string.h,v 1.1.1.1 2016/01/10 21:36:17 christos Exp $ */
2
3 /* Description of GNU message catalog format: string hashing function.
4 Copyright (C) 1995, 1997, 1998, 2000, 2001 Free Software Foundation, Inc.
5
6 This program is free software; you can redistribute it and/or modify it
7 under the terms of the GNU Library General Public License as published
8 by the Free Software Foundation; either version 2, or (at your option)
9 any later version.
10
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Library General Public License for more details.
15
16 You should have received a copy of the GNU Library General Public
17 License along with this program; if not, write to the Free Software
18 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
19 USA. */
20
21 /* @@ end of prolog @@ */
22
23 #ifndef PARAMS
24 # if __STDC__ || defined __GNUC__ || defined __SUNPRO_C || defined __cplusplus || __PROTOTYPES
25 # define PARAMS(Args) Args
26 # else
27 # define PARAMS(Args) ()
28 # endif
29 #endif
30
31 /* We assume to have `unsigned long int' value with at least 32 bits. */
32 #define HASHWORDBITS 32
33
34
35 /* Defines the so called `hashpjw' function by P.J. Weinberger
36 [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools,
37 1986, 1987 Bell Telephone Laboratories, Inc.] */
38 static unsigned long int hash_string PARAMS ((const char *__str_param));
39
40 static inline unsigned long int
hash_string(str_param)41 hash_string (str_param)
42 const char *str_param;
43 {
44 unsigned long int hval, g;
45 const char *str = str_param;
46
47 /* Compute the hash value for the given string. */
48 hval = 0;
49 while (*str != '\0')
50 {
51 hval <<= 4;
52 hval += (unsigned long int) *str++;
53 g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4));
54 if (g != 0)
55 {
56 hval ^= g >> (HASHWORDBITS - 8);
57 hval ^= g;
58 }
59 }
60 return hval;
61 }
62