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dd9423a6 | 1 | /* Implements a string hashing function. |
dff8da6b | 2 | Copyright (C) 1995-2024 Free Software Foundation, Inc. |
dd9423a6 UD |
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 | 16 | License along with the GNU C Library; if not, see |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
dd9423a6 | 18 | |
6d248857 WN |
19 | #ifdef HAVE_CONFIG_H |
20 | # include <config.h> | |
21 | #endif | |
22 | ||
23 | /* Specification. */ | |
dd9423a6 UD |
24 | #include "hash-string.h" |
25 | ||
26 | ||
27 | /* Defines the so called `hashpjw' function by P.J. Weinberger | |
28 | [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools, | |
29 | 1986, 1987 Bell Telephone Laboratories, Inc.] */ | |
30 | unsigned long int | |
6d248857 | 31 | __hash_string (const char *str_param) |
dd9423a6 UD |
32 | { |
33 | unsigned long int hval, g; | |
34 | const char *str = str_param; | |
35 | ||
36 | /* Compute the hash value for the given string. */ | |
37 | hval = 0; | |
38 | while (*str != '\0') | |
39 | { | |
40 | hval <<= 4; | |
d0f1175e | 41 | hval += (unsigned char) *str++; |
dd9423a6 UD |
42 | g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4)); |
43 | if (g != 0) | |
44 | { | |
45 | hval ^= g >> (HASHWORDBITS - 8); | |
46 | hval ^= g; | |
47 | } | |
48 | } | |
49 | return hval; | |
50 | } |