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, write to the Free
17   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
18   02111-1307 USA.  */
19
20#include <errno.h>
21#include <stdlib.h>
22#include <limits.h>
23#include <stdint.h>
24#include <sys/types.h>
25
26/* Global state for non-reentrant functions.  */
27struct drand48_data __libc_drand48_data;
28
29
30int
31__drand48_iterate (xsubi, buffer)
32     unsigned short int xsubi[3];
33     struct drand48_data *buffer;
34{
35  uint64_t X;
36  uint64_t result;
37
38  /* Initialize buffer, if not yet done.  */
39  if (__builtin_expect (!buffer->__init, 0))
40    {
41      buffer->__a = 0x5deece66dull;
42      buffer->__c = 0xb;
43      buffer->__init = 1;
44    }
45
46  /* Do the real work.  We choose a data type which contains at least
47     48 bits.  Because we compute the modulus it does not care how
48     many bits really are computed.  */
49
50  X = (uint64_t) xsubi[2] << 32 | (uint32_t) xsubi[1] << 16 | xsubi[0];
51
52  result = X * buffer->__a + buffer->__c;
53
54  xsubi[0] = result & 0xffff;
55  xsubi[1] = (result >> 16) & 0xffff;
56  xsubi[2] = (result >> 32) & 0xffff;
57
58  return 0;
59}
60