1/* Copyright (C) 1995,1996,1997,2002,2003 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, write to the Free
16   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
17   02111-1307 USA.  */
18
19#include "gmp.h"
20#include "gmp-impl.h"
21#include <ieee754.h>
22#include <float.h>
23
24/* Convert a multi-precision integer of the needed number of bits (53 for
25   double) and an integral power of two to a `double' in IEEE754 double-
26   precision format.  */
27
28double
29__mpn_construct_double (mp_srcptr frac_ptr, int expt, int negative)
30{
31  union ieee754_double u;
32
33  u.ieee.negative = negative;
34  u.ieee.exponent = expt + IEEE754_DOUBLE_BIAS;
35#if BITS_PER_MP_LIMB == 32
36  u.ieee.mantissa1 = frac_ptr[0];
37  u.ieee.mantissa0 = frac_ptr[1] & (((mp_limb_t) 1
38				     << (DBL_MANT_DIG - 32)) - 1);
39#elif BITS_PER_MP_LIMB == 64
40  u.ieee.mantissa1 = frac_ptr[0] & (((mp_limb_t) 1 << 32) - 1);
41  u.ieee.mantissa0 = (frac_ptr[0] >> 32) & (((mp_limb_t) 1
42					     << (DBL_MANT_DIG - 32)) - 1);
43#else
44  #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"
45#endif
46
47  return u.d;
48}
49