Update.
[glibc.git] / intl / hash-string.h
blob32ca018bdaad80286b3cb38086528a44e8a0930b
1 /* Implements a string hashing function.
2 Copyright (C) 1995, 1997, 1998 Free Software Foundation, Inc.
4 This file is part of the GNU C Library. Its master source is NOT part of
5 the C library, however.
7 The GNU C Library is free software; you can redistribute it and/or
8 modify it under the terms of the GNU Library General Public License as
9 published by the Free Software Foundation; either version 2 of the
10 License, or (at your option) any later version.
12 The GNU C Library is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Library General Public License for more details.
17 You should have received a copy of the GNU Library General Public
18 License along with the GNU C Library; see the file COPYING.LIB. If not,
19 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
22 /* @@ end of prolog @@ */
24 #ifndef PARAMS
25 # if __STDC__
26 # define PARAMS(Args) Args
27 # else
28 # define PARAMS(Args) ()
29 # endif
30 #endif
32 /* We assume to have `unsigned long int' value with at least 32 bits. */
33 #define HASHWORDBITS 32
36 /* Defines the so called `hashpjw' function by P.J. Weinberger
37 [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools,
38 1986, 1987 Bell Telephone Laboratories, Inc.] */
39 static unsigned long int hash_string PARAMS ((const char *__str_param));
41 static inline unsigned long int
42 hash_string (str_param)
43 const char *str_param;
45 unsigned long int hval, g;
46 const char *str = str_param;
48 /* Compute the hash value for the given string. */
49 hval = 0;
50 while (*str != '\0')
52 hval <<= 4;
53 hval += (unsigned long int) *str++;
54 g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4));
55 if (g != 0)
57 hval ^= g >> (HASHWORDBITS - 8);
58 hval ^= g;
61 return hval;