/[zanavi_public1]/navit/intl/hash-string.h
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Contents of /navit/intl/hash-string.h

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Fri Oct 28 21:19:04 2011 UTC (8 years, 11 months ago) by zoff99
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1 zoff99 2 /* 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
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     }

   
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