1/* Copyright (C) 1995-2023 Free Software Foundation, Inc.
2 This file is part of the GNU C Library.
3
4 The GNU C Library is free software; you can redistribute it and/or
5 modify it under the terms of the GNU Lesser General Public
6 License as published by the Free Software Foundation; either
7 version 2.1 of the License, or (at your option) any later version.
8
9 The GNU C Library is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 Lesser General Public License for more details.
13
14 You should have received a copy of the GNU Lesser General Public
15 License along with the GNU C Library; if not, see
16 <https://www.gnu.org/licenses/>. */
17
18#include <errno.h>
19#include <stdlib.h>
20#include <limits.h>
21#include <stdint.h>
22#include <sys/types.h>
23
24/* Global state for non-reentrant functions. */
25struct drand48_data __libc_drand48_data;
26
27
28int
29__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 (__glibc_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