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1 /* Description of GNU message catalog format: string hashing function.
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2 Copyright (C) 1995, 1997, 1998, 2000, 2001 Free Software Foundation, Inc.
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3
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4 This program is free software; you can redistribute it and/or modify it
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5 under the terms of the GNU Library General Public License as published
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6 by the Free Software Foundation; either version 2, or (at your option)
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7 any later version.
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8
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9 This program is distributed in the hope that it will be useful,
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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
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12 Library General Public License for more details.
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13
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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
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16 Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301,
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17 USA. */
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18
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19 /* @@ end of prolog @@ */
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20
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21 #ifndef PARAMS
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22 # if __STDC__ || defined __GNUC__ || defined __SUNPRO_C || defined __cplusplus || __PROTOTYPES
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23 # define PARAMS(Args) Args
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24 # else
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25 # define PARAMS(Args) ()
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26 # endif
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27 #endif
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28
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29 /* We assume to have `unsigned long int' value with at least 32 bits. */
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30 #define HASHWORDBITS 32
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31
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32
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33 /* Defines the so called `hashpjw' function by P.J. Weinberger
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34 [see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools,
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35 1986, 1987 Bell Telephone Laboratories, Inc.] */
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36 static unsigned long int hash_string PARAMS ((const char *__str_param));
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37
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38 static inline unsigned long int
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39 hash_string (str_param)
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40 const char *str_param;
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41 {
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42 unsigned long int hval, g;
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43 const char *str = str_param;
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44
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45 /* Compute the hash value for the given string. */
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46 hval = 0;
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47 while (*str != '\0')
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48 {
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49 hval <<= 4;
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50 hval += (unsigned long int) *str++;
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51 g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4));
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52 if (g != 0)
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53 {
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54 hval ^= g >> (HASHWORDBITS - 8);
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55 hval ^= g;
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56 }
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57 }
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58 return hval;
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59 }
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