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52 lines
1.7 KiB
C
52 lines
1.7 KiB
C
/* Implements hashing function for string with known length.
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Copyright (C) 1996-2017 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library 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 GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <sys/types.h>
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/* We assume to have `size_t' 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 size_t hash_string (const char *__str_param, size_t __len);
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static inline size_t
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hash_string (const char *str_param, size_t len)
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{
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size_t hval, g;
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const char *end_str = str_param + len;
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/* Compute the hash value for the given string. */
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hval = len;
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while (str_param != end_str)
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{
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hval <<= 4;
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hval += (size_t) *str_param++;
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g = hval & ((size_t) 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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