1 /* Reentrant random function frm POSIX.1c.
2 Copyright (C) 1996, 1999 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@cygnus.com <mailto:drepper@cygnus.com>>, 1996.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, see
18 <http://www.gnu.org/licenses/>. */
19
20 #include <stdlib.h>
21
22
23 /* This algorithm is mentioned in the ISO C standard, here extended
24 for 32 bits. */
rand_r(unsigned int * seed)25 int rand_r (unsigned int *seed)
26 {
27 unsigned int next = *seed;
28 int result;
29
30 next *= 1103515245;
31 next += 12345;
32 result = (unsigned int) (next / 65536) % 2048;
33
34 next *= 1103515245;
35 next += 12345;
36 result <<= 10;
37 result ^= (unsigned int) (next / 65536) % 1024;
38
39 next *= 1103515245;
40 next += 12345;
41 result <<= 10;
42 result ^= (unsigned int) (next / 65536) % 1024;
43
44 *seed = next;
45
46 return result;
47 }
48