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/* hash.c - The gdbm hash function. */
/* This file is part of GDBM, the GNU data base manager, by Philip A. Nelson.
Copyright (C) 1990, 1991, 1993 Free Software Foundation, Inc.
GDBM is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
GDBM 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with GDBM; see the file COPYING. If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
You may contact the author by:
e-mail: phil@cs.wwu.edu
us-mail: Philip A. Nelson
Computer Science Department
Western Washington University
Bellingham, WA 98226
*************************************************************************/
/* include system configuration before all else. */
#include "autoconf.h"
#include "gdbmdefs.h"
/* This hash function computes a 31 bit value. The value is used to index
the hash directory using the top n bits. It is also used in a hash bucket
to find the home position of the element by taking the value modulo the
bucket hash table size. */
word_t
_gdbm_hash (key)
datum key;
{
#if LONG_64_BITS || !INT_16_BITS
unsigned int value; /* Used to compute the hash value. */
#else
unsigned long value; /* Used to compute the hash value. */
#endif
int index; /* Used to cycle through random values. */
/* Set the initial value from key. */
value = 0x238F13AF * key.dsize;
for (index = 0; index < key.dsize; index++)
value = (value + (key.dptr[index] << (index*5 % 24))) & 0x7FFFFFFF;
value = (1103515243 * value + 12345) & 0x7FFFFFFF;
/* Return the value. */
return((word_t) value);
}
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