Test limits.h macros instead of sizeof for determining size of types.
[kopensolaris-gnu/glibc.git] / stdlib / drand48-iter.c
1 /* Copyright (C) 1995, 1996 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 Library General Public License as
7 published by the Free Software Foundation; either version 2 of the
8 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 Library General Public License for more details.
14
15 You should have received a copy of the GNU Library General Public
16 License along with the GNU C Library; see the file COPYING.LIB.  If
17 not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
18 Boston, MA 02111-1307, USA.  */
19
20 #include <errno.h>
21 #include <stdlib.h>
22 #include <limits.h>
23
24
25 /* Global state for non-reentrent functions.  */
26 struct drand48_data __libc_drand48_data;
27
28
29 int
30 __drand48_iterate (xsubi, buffer)
31      unsigned short int xsubi[3];
32      struct drand48_data *buffer;
33 {
34   /* Be generous for the arguments, detect some errors.  */
35   if (xsubi == NULL || buffer == NULL)
36     {
37       errno = EFAULT;
38       return -1;
39     }
40
41   /* Initialize buffer, if not yet done.  */
42   if (!buffer->init)
43     {
44 #if (USHRT_MAX == 0xffffU)
45       buffer->a[2] = 0x5;
46       buffer->a[1] = 0xdeec;
47       buffer->a[0] = 0xe66d;
48 #else
49       buffer->a[2] = 0x5deecUL;
50       buffer->a[1] = 0xe66d0000UL;
51       buffer->a[0] = 0;
52 #endif
53       buffer->c = 0xb;
54       buffer->init = 1;
55     }
56
57   /* Do the real work.  We choose a data type which contains at least
58      48 bits.  Because we compute the modulus it does not care how
59      many bits really are computed.  */
60
61   if (sizeof (long int) >= 6)
62     {
63       /* The `long' data type is sufficent.  */
64       unsigned long int X, a, result;
65
66 #define ONE_STEP                                                            \
67       if (sizeof (unsigned short int) == 2)                                 \
68         {                                                                   \
69           X = (xsubi[2] << 16 | xsubi[1]) << 16 | xsubi[0];                 \
70           a = (buffer->a[2] << 16 | buffer->a[1]) << 16 | buffer->a[0];     \
71                                                                             \
72           result = X * a + buffer->c;                                       \
73                                                                             \
74           xsubi[0] = result & 0xffff;                                       \
75           result >>= 16;                                                    \
76           xsubi[1] = result & 0xffff;                                       \
77           result >>= 16;                                                    \
78           xsubi[2] = result & 0xffff;                                       \
79         }                                                                   \
80       else                                                                  \
81         {                                                                   \
82           X = xsubi[2] << 16 | xsubi[1] >> 16;                              \
83           a = buffer->a[2] << 16 | buffer->a[1] >> 16;                      \
84                                                                             \
85           result = X * a + buffer->c;                                       \
86                                                                             \
87           xsubi[0] = result >> 16 & 0xffffffffl;                            \
88           xsubi[1] = result << 16 & 0xffff0000l;                            \
89         }
90       ONE_STEP;
91     }
92   else
93     {
94       /* We have to use the `long long' data type.  */
95       unsigned long long int X, a, result;
96       ONE_STEP;
97     }
98
99   return 0;
100 }