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/* __gmp_insert_double -- convert from array of mp_limb_t to double.
Copyright (C) 1996, 1997, 1999 Free Software Foundation, Inc.
This file is part of the GNU MP Library.
The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Library General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
License for more details.
You should have received a copy of the GNU Library General Public License
along with the GNU MP Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */
#include "gmp.h"
#include "gmp-impl.h"
#ifdef XDEBUG
#undef _GMP_IEEE_FLOATS
#endif
#ifndef _GMP_IEEE_FLOATS
#define _GMP_IEEE_FLOATS 0
#endif
double
#if __STDC__
__gmp_scale2 (double d, int exp)
#else
__gmp_scale2 (d, exp)
double d;
int exp;
#endif
{
#if _GMP_IEEE_FLOATS
{
union ieee_double_extract x;
x.d = d;
exp += x.s.exp;
x.s.exp = exp;
if (exp >= 2047)
{
/* Return +-infinity */
x.s.exp = 2047;
x.s.manl = x.s.manh = 0;
}
else if (exp < 1)
{
x.s.exp = 1; /* smallest exponent (biased) */
/* Divide result by 2 until we have scaled it to the right IEEE
denormalized number, but stop if it becomes zero. */
while (exp < 1 && x.d != 0)
{
x.d *= 0.5;
exp++;
}
}
return x.d;
}
#else
{
double factor, r;
factor = 2.0;
if (exp < 0)
{
factor = 0.5;
exp = -exp;
}
r = d;
if (exp != 0)
{
if ((exp & 1) != 0)
r *= factor;
exp >>= 1;
while (exp != 0)
{
factor *= factor;
if ((exp & 1) != 0)
r *= factor;
exp >>= 1;
}
}
return r;
}
#endif
}
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