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comparison intl/hash-string.h @ 0:a06113de4d67

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author kent <kent@cr.ie.u-ryukyu.ac.jp>
date Fri, 17 Jul 2009 14:47:48 +0900
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1 /* Description of GNU message catalog format: string hashing function.
2 Copyright (C) 1995, 1997, 1998, 2000, 2001 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., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301,
17 USA. */
18
19 /* @@ end of prolog @@ */
20
21 #ifndef PARAMS
22 # if __STDC__ || defined __GNUC__ || defined __SUNPRO_C || defined __cplusplus || __PROTOTYPES
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 int hash_string PARAMS ((const char *__str_param));
37
38 static inline unsigned long int
39 hash_string (str_param)
40 const char *str_param;
41 {
42 unsigned long int hval, g;
43 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 int) *str++;
51 g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4));
52 if (g != 0)
53 {
54 hval ^= g >> (HASHWORDBITS - 8);
55 hval ^= g;
56 }
57 }
58 return hval;
59 }