61 lines
1.8 KiB
C
61 lines
1.8 KiB
C
/* Implements a string hashing function.
|
|
Copyright (C) 1995, 1997, 1998, 2000 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
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, write to the Free
|
|
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
|
|
02111-1307 USA. */
|
|
|
|
/* @@ end of prolog @@ */
|
|
|
|
#ifndef PARAMS
|
|
# if __STDC__
|
|
# define PARAMS(Args) Args
|
|
# else
|
|
# define PARAMS(Args) ()
|
|
# endif
|
|
#endif
|
|
|
|
/* We assume to have `unsigned long int' 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 unsigned long int hash_string PARAMS ((const char *__str_param));
|
|
|
|
static inline unsigned long int
|
|
hash_string (str_param)
|
|
const char *str_param;
|
|
{
|
|
unsigned long int hval, g;
|
|
const char *str = str_param;
|
|
|
|
/* Compute the hash value for the given string. */
|
|
hval = 0;
|
|
while (*str != '\0')
|
|
{
|
|
hval <<= 4;
|
|
hval += (unsigned long int) *str++;
|
|
g = hval & ((unsigned long int) 0xf << (HASHWORDBITS - 4));
|
|
if (g != 0)
|
|
{
|
|
hval ^= g >> (HASHWORDBITS - 8);
|
|
hval ^= g;
|
|
}
|
|
}
|
|
return hval;
|
|
}
|