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glibc/locale/strlen-hash.h
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/* Implements hashing function for string with known length. | |
Copyright (C) 1996-2016 Free Software Foundation, Inc. | |
This file is part of the GNU C Library. | |
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996. | |
The GNU C Library is free software; you can redistribute it and/or | |
modify it under the terms of the GNU Lesser General Public | |
License as published by the Free Software Foundation; either | |
version 2.1 of the License, or (at your option) any later version. | |
The GNU C Library is distributed in the hope that it will be useful, | |
but WITHOUT ANY WARRANTY; without even the implied warranty of | |
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
Lesser General Public License for more details. | |
You should have received a copy of the GNU Lesser General Public | |
License along with the GNU C Library; if not, see | |
<http://www.gnu.org/licenses/>. */ | |
#include <sys/types.h> | |
/* We assume to have `size_t' value with at least 32 bits. */ | |
#define HASHWORDBITS 32 | |
/* Defines the so called `hashpjw' function by P.J. Weinberger | |
[see Aho/Sethi/Ullman, COMPILERS: Principles, Techniques and Tools, | |
1986, 1987 Bell Telephone Laboratories, Inc.] */ | |
static size_t hash_string (const char *__str_param, size_t __len); | |
static inline size_t | |
hash_string (const char *str_param, size_t len) | |
{ | |
size_t hval, g; | |
const char *end_str = str_param + len; | |
/* Compute the hash value for the given string. */ | |
hval = len; | |
while (str_param != end_str) | |
{ | |
hval <<= 4; | |
hval += (size_t) *str_param++; | |
g = hval & ((size_t) 0xf << (HASHWORDBITS - 4)); | |
if (g != 0) | |
{ | |
hval ^= g >> (HASHWORDBITS - 8); | |
hval ^= g; | |
} | |
} | |
return hval; | |
} |