1 /* Copyright (C) 1995-2022 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.  */
25 struct drand48_data __libc_drand48_data;
26 
27 
28 int
__drand48_iterate(unsigned short int xsubi[3],struct drand48_data * buffer)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