Update.
[glibc.git] / intl / hash-string.h
blobae4bcfb3e219c65df15680de92cc02352e56d6e3
1 /* Implements a string hashing function.
2 Copyright (C) 1995, 1997, 1998, 2000 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, write to the Free
17 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
18 02111-1307 USA. */
20 /* @@ end of prolog @@ */
22 #ifndef PARAMS
23 # if __STDC__
24 # define PARAMS(Args) Args
25 # else
26 # define PARAMS(Args) ()
27 # endif
28 #endif
30 /* We assume to have `unsigned long int' value with at least 32 bits. */
31 #define HASHWORDBITS 32
34 /* Defines the so called `hashpjw' function by P.J. Weinberger
35 [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools,
36 1986, 1987 Bell Telephone Laboratories, Inc.] */
37 static unsigned long int hash_string PARAMS ((const char *__str_param));
39 static inline unsigned long int
40 hash_string (str_param)
41 const char *str_param;
43 unsigned long int hval, g;
44 const char *str = str_param;
46 /* Compute the hash value for the given string. */
47 hval = 0;
48 while (*str != '\0')
50 hval <<= 4;
51 hval += (unsigned long int) *str++;
52 g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4));
53 if (g != 0)
55 hval ^= g >> (HASHWORDBITS - 8);
56 hval ^= g;
59 return hval;