57 lines
1.6 KiB
C
57 lines
1.6 KiB
C
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/* hash-string - Implements a string hashing function.
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Copyright (C) 1995 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 General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
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#ifdef HAVE_VALUES_H
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# include <values.h>
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#endif
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/* @@ end of prolog @@ */
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#ifndef BITSPERBYTE
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# define BITSPERBYTE 8
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#endif
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#ifndef LONGBITS
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# define LONGBITS (sizeof (long) * BITSPERBYTE)
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#endif /* LONGBITS */
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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 inline unsigned long
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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 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) *str++;
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g = hval & ((unsigned long) 0xf << (LONGBITS - 4));
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if (g != 0)
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{
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hval ^= g >> (LONGBITS - 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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