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60 lines
1.8 KiB
C
60 lines
1.8 KiB
C
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/* Implements a string hashing function.
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Copyright (C) 1995, 1997 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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/* @@ end of prolog @@ */
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#ifndef PARAMS
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# if __STDC__
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# define PARAMS(Args) Args
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# else
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# define PARAMS(Args) ()
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# endif
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#endif
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/* We assume to have `unsigned long int' value with at least 32 bits. */
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#define HASHWORDBITS 32
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/* Defines the so called `hashpjw' function by P.J. Weinberger
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[see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools,
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1986, 1987 Bell Telephone Laboratories, Inc.] */
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static unsigned long int hash_string PARAMS ((const char *__str_param));
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static inline unsigned long int
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hash_string (str_param)
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const char *str_param;
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{
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unsigned long int hval, g;
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const char *str = str_param;
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/* Compute the hash value for the given string. */
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hval = 0;
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while (*str != '\0')
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{
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hval <<= 4;
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hval += (unsigned long int) *str++;
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g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4));
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if (g != 0)
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{
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hval ^= g >> (HASHWORDBITS - 8);
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hval ^= g;
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}
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}
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return hval;
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}
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