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dd9423a6 UD |
1 | /* Implements a string hashing function. |
2 | Copyright (C) 1995, 1997, 1998, 2000, 2003 Free Software Foundation, Inc. | |
3 | This file is part of the GNU C Library. | |
4 | ||
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. | |
9 | ||
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. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
59ba27a6 PE |
16 | License along with the GNU C Library; if not, see |
17 | <http://www.gnu.org/licenses/>. */ | |
dd9423a6 UD |
18 | |
19 | #include "hash-string.h" | |
20 | ||
21 | ||
22 | /* Defines the so called `hashpjw' function by P.J. Weinberger | |
23 | [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools, | |
24 | 1986, 1987 Bell Telephone Laboratories, Inc.] */ | |
25 | unsigned long int | |
26 | __hash_string (str_param) | |
27 | const char *str_param; | |
28 | { | |
29 | unsigned long int hval, g; | |
30 | const char *str = str_param; | |
31 | ||
32 | /* Compute the hash value for the given string. */ | |
33 | hval = 0; | |
34 | while (*str != '\0') | |
35 | { | |
36 | hval <<= 4; | |
d0f1175e | 37 | hval += (unsigned char) *str++; |
dd9423a6 UD |
38 | g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4)); |
39 | if (g != 0) | |
40 | { | |
41 | hval ^= g >> (HASHWORDBITS - 8); | |
42 | hval ^= g; | |
43 | } | |
44 | } | |
45 | return hval; | |
46 | } |