mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-18 00:41:06 +00:00
44 lines
1.6 KiB
C
44 lines
1.6 KiB
C
/* Implement simple hashing table with string based keys.
|
|
Copyright (C) 1994-1997, 2000, 2001, 2002 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
Written by Ulrich Drepper <drepper@gnu.ai.mit.edu>, October 1994.
|
|
|
|
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/>. */
|
|
|
|
#ifndef hashval_t
|
|
# define hashval_t unsigned long int
|
|
#endif
|
|
#include <limits.h> /* For CHAR_BIT. */
|
|
|
|
hashval_t
|
|
compute_hashval (const void *key, size_t keylen)
|
|
{
|
|
size_t cnt;
|
|
hashval_t hval;
|
|
|
|
/* Compute the hash value for the given string. The algorithm
|
|
is taken from [Aho,Sethi,Ullman], modified to reduce the number of
|
|
collisions for short strings with very varied bit patterns.
|
|
See http://www.clisp.org/haible/hashfunc.html. */
|
|
cnt = 0;
|
|
hval = keylen;
|
|
while (cnt < keylen)
|
|
{
|
|
hval = (hval << 9) | (hval >> (sizeof hval * CHAR_BIT - 9));
|
|
hval += (hashval_t) *(((char *) key) + cnt++);
|
|
}
|
|
return hval != 0 ? hval : ~((hashval_t) 0);
|
|
}
|