1/* Copyright (C) 1995-2020 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 <https://www.gnu.org/licenses/>. */
18
19#include <errno.h>
20#include <stdlib.h>
21#include <limits.h>
22#include <stdint.h>
23#include <sys/types.h>
24
25/* Global state for non-reentrant functions. */
26struct drand48_data __libc_drand48_data;
27
28
29int
30__drand48_iterate (unsigned short int xsubi[3], struct drand48_data *buffer)
31{
32 uint64_t X;
33 uint64_t result;
34
35 /* Initialize buffer, if not yet done. */
36 if (__glibc_unlikely (!buffer->__init))
37 {
38 buffer->__a = 0x5deece66dull;
39 buffer->__c = 0xb;
40 buffer->__init = 1;
41 }
42
43 /* Do the real work. We choose a data type which contains at least
44 48 bits. Because we compute the modulus it does not care how
45 many bits really are computed. */
46
47 X = (uint64_t) xsubi[2] << 32 | (uint32_t) xsubi[1] << 16 | xsubi[0];
48
49 result = X * buffer->__a + buffer->__c;
50
51 xsubi[0] = result & 0xffff;
52 xsubi[1] = (result >> 16) & 0xffff;
53 xsubi[2] = (result >> 32) & 0xffff;
54
55 return 0;
56}
57