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[glibc/history.git] / stdlib / rand_r.c
blob3d49c92de65d338e6aae87c8b1e98187fb0080fb
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>, 1996.
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.
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.
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; if not, write to the Free
18 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
19 02111-1307 USA. */
21 #include <stdlib.h>
24 /* This algorithm is mentioned in the ISO C standard, here extended
25 for 32 bits. */
26 int
27 rand_r (unsigned int *seed)
29 unsigned int next = *seed;
30 int result;
32 next *= 1103515245;
33 next += 12345;
34 result = (unsigned int) (next / 65536) % 2048;
36 next *= 1103515245;
37 next += 12345;
38 result <<= 10;
39 result ^= (unsigned int) (next / 65536) % 1024;
41 next *= 1103515245;
42 next += 12345;
43 result <<= 10;
44 result ^= (unsigned int) (next / 65536) % 1024;
46 *seed = next;
48 return result;