Update.
[glibc.git] / stdlib / erand48_r.c
blob85393b79f6667566c91a11081dc0a21007fc4b40
1 /* Copyright (C) 1995, 1997 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.
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.
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.
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 not,
17 write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
18 Boston, MA 02111-1307, USA. */
20 #include <ieee754.h>
21 #include <stdlib.h>
22 #include <limits.h>
25 int
26 __erand48_r (xsubi, buffer, result)
27 unsigned short int xsubi[3];
28 struct drand48_data *buffer;
29 double *result;
31 union ieee754_double temp;
33 /* Compute next state. */
34 if (__drand48_iterate (xsubi, buffer) < 0)
35 return -1;
37 /* Construct a positive double with the 48 random bits distributed over
38 its fractional part so the resulting FP number is [0.0,1.0). */
40 #if USHRT_MAX == 65535
41 temp.ieee.negative = 0;
42 temp.ieee.exponent = IEEE754_DOUBLE_BIAS;
43 temp.ieee.mantissa0 = (xsubi[2] << 4) | (xsubi[1] >> 12);
44 temp.ieee.mantissa1 = ((xsubi[1] & 0xfff) << 20) | (xsubi[0] << 4);
45 #elif USHRT_MAX == 2147483647
46 temp.ieee.negative = 0;
47 temp.ieee.exponent = IEEE754_DOUBLE_BIAS;
48 temp.ieee.mantissa0 = (xsubi[1] << 4) | (xsubi[0] >> 28);
49 temp.ieee.mantissa1 = ((xsubi[0] & 0xfffffff) << 4);
50 #else
51 # error Unsupported size of short int
52 #endif
54 /* Please note the lower 4 bits of mantissa1 are always 0. */
55 *result = temp.d - 1.0;
57 return 0;
59 weak_alias (__erand48_r, erand48_r)