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1 | /* Description of GNU message catalog format: string hashing function. |
2 | Copyright (C) 1995, 1997, 1998, 2000, 2001 Free Software Foundation, Inc. | |
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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) | |
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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 | |
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11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
12 | Library General Public License for more details. | |
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13 | |
14 | You should have received a copy of the GNU Library General Public | |
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15 | License along with this program; if not, write to the Free Software |
16 | Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, | |
17 | USA. */ | |
252b5132 | 18 | |
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19 | /* @@ end of prolog @@ */ |
20 | ||
21 | #ifndef PARAMS | |
bf070c84 | 22 | # if __STDC__ || defined __GNUC__ || defined __SUNPRO_C || defined __cplusplus || __PROTOTYPES |
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23 | # define PARAMS(Args) Args |
24 | # else | |
25 | # define PARAMS(Args) () | |
26 | # endif | |
27 | #endif | |
28 | ||
29 | /* We assume to have `unsigned long int' value with at least 32 bits. */ | |
30 | #define HASHWORDBITS 32 | |
31 | ||
32 | ||
33 | /* Defines the so called `hashpjw' function by P.J. Weinberger | |
34 | [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools, | |
35 | 1986, 1987 Bell Telephone Laboratories, Inc.] */ | |
bf070c84 | 36 | static unsigned long int hash_string PARAMS ((const char *__str_param)); |
252b5132 | 37 | |
bf070c84 | 38 | static inline unsigned long int |
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39 | hash_string (str_param) |
40 | const char *str_param; | |
41 | { | |
42 | unsigned long int hval, g; | |
43 | const char *str = str_param; | |
44 | ||
45 | /* Compute the hash value for the given string. */ | |
46 | hval = 0; | |
47 | while (*str != '\0') | |
48 | { | |
49 | hval <<= 4; | |
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50 | hval += (unsigned long int) *str++; |
51 | g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4)); | |
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52 | if (g != 0) |
53 | { | |
54 | hval ^= g >> (HASHWORDBITS - 8); | |
55 | hval ^= g; | |
56 | } | |
57 | } | |
58 | return hval; | |
59 | } |