1 /* Copyright (C) 1995, 1996, 2001 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3 Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>, August 1995.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
18
19 #include <errno.h>
20 #include <stdlib.h>
21 #include <limits.h>
22 #include <stdint.h>
23 #include <stdlib.h>
24 #include <sys/types.h>
25
26 /* Global state for non-reentrant functions. */
27 struct drand48_data __libc_drand48_data;
28
__drand48_iterate(unsigned short int xsubi[3],struct drand48_data * buffer)29 int __drand48_iterate (unsigned short int xsubi[3], struct drand48_data *buffer)
30 {
31 uint64_t X;
32 uint64_t result;
33
34 /* Initialize buffer, if not yet done. */
35 if (unlikely(!buffer->__init))
36 {
37 buffer->__a = 0x5deece66dull;
38 buffer->__c = 0xb;
39 buffer->__init = 1;
40 }
41
42 /* Do the real work. We choose a data type which contains at least
43 48 bits. Because we compute the modulus it does not care how
44 many bits really are computed. */
45
46 X = (uint64_t) xsubi[2] << 32 | (uint32_t) xsubi[1] << 16 | xsubi[0];
47
48 result = X * buffer->__a + buffer->__c;
49
50 xsubi[0] = result & 0xffff;
51 xsubi[1] = (result >> 16) & 0xffff;
52 xsubi[2] = (result >> 32) & 0xffff;
53
54 return 0;
55 }
56