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3185942a | 1 | /* hash-string.h - Description of GNU message catalog format: string hashing function. */ |
b80f6443 | 2 | |
3185942a | 3 | /* Copyright (C) 1995, 1997, 1998, 2000, 2001, 2005-2009 Free Software Foundation, Inc. |
b80f6443 | 4 | |
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5 | This file is part of GNU Bash. |
6 | ||
7 | Bash is free software: you can redistribute it and/or modify | |
8 | it under the terms of the GNU General Public License as published by | |
9 | the Free Software Foundation, either version 3 of the License, or | |
10 | (at your option) any later version. | |
11 | ||
12 | Bash is distributed in the hope that it will be useful, | |
b80f6443 | 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
15 | GNU General Public License for more details. | |
b80f6443 | 16 | |
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17 | You should have received a copy of the GNU General Public License |
18 | along with Bash. If not, see <http://www.gnu.org/licenses/>. | |
19 | */ | |
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20 | |
21 | /* @@ end of prolog @@ */ | |
22 | ||
23 | #ifndef PARAMS | |
24 | # if __STDC__ || defined __GNUC__ || defined __SUNPRO_C || defined __cplusplus || __PROTOTYPES | |
25 | # define PARAMS(Args) Args | |
26 | # else | |
27 | # define PARAMS(Args) () | |
28 | # endif | |
29 | #endif | |
30 | ||
31 | /* We assume to have `unsigned long int' value with at least 32 bits. */ | |
32 | #define HASHWORDBITS 32 | |
33 | ||
34 | ||
35 | /* Defines the so called `hashpjw' function by P.J. Weinberger | |
36 | [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools, | |
37 | 1986, 1987 Bell Telephone Laboratories, Inc.] */ | |
38 | static unsigned long int hash_string PARAMS ((const char *__str_param)); | |
39 | ||
40 | static inline unsigned long int | |
41 | hash_string (str_param) | |
42 | const char *str_param; | |
43 | { | |
44 | unsigned long int hval, g; | |
45 | const char *str = str_param; | |
46 | ||
47 | /* Compute the hash value for the given string. */ | |
48 | hval = 0; | |
49 | while (*str != '\0') | |
50 | { | |
51 | hval <<= 4; | |
52 | hval += (unsigned long int) *str++; | |
53 | g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4)); | |
54 | if (g != 0) | |
55 | { | |
56 | hval ^= g >> (HASHWORDBITS - 8); | |
57 | hval ^= g; | |
58 | } | |
59 | } | |
60 | return hval; | |
61 | } |