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/* mpfr_get_f -- convert a MPFR number to a GNU MPF number
Copyright 2005-2017 Free Software Foundation, Inc.
Contributed by the AriC and Caramba projects, INRIA.
This file is part of the GNU MPFR Library.
The GNU MPFR Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 3 of the License, or (at your
option) any later version.
The GNU MPFR 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 Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the GNU MPFR Library; see the file COPYING.LESSER. If not, see
http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
#include "mpfr-impl.h"
/* Since MPFR-3.0, return the usual inexact value.
The erange flag is set if an error occurred in the conversion
(y is NaN, +Inf, or -Inf that have no equivalent in mpf)
*/
int
mpfr_get_f (mpf_ptr x, mpfr_srcptr y, mpfr_rnd_t rnd_mode)
{
int inex;
mp_size_t sx, sy;
mpfr_prec_t precx, precy;
mp_limb_t *xp;
int sh;
if (MPFR_UNLIKELY(MPFR_IS_SINGULAR(y)))
{
if (MPFR_IS_ZERO(y))
{
mpf_set_ui (x, 0);
return 0;
}
else if (MPFR_IS_NAN (y))
{
MPFR_SET_ERANGE ();
return 0;
}
else /* y is plus infinity (resp. minus infinity), set x to the maximum
value (resp. the minimum value) in precision PREC(x) */
{
int i;
mp_limb_t *xp;
MPFR_SET_ERANGE ();
/* To this day, [mp_exp_t] and mp_size_t are #defined as the same
type */
EXP (x) = MP_SIZE_T_MAX;
sx = PREC (x);
SIZ (x) = sx;
xp = PTR (x);
for (i = 0; i < sx; i++)
xp[i] = MP_LIMB_T_MAX;
if (MPFR_IS_POS (y))
return -1;
else
{
mpf_neg (x, x);
return +1;
}
}
}
sx = PREC(x); /* number of limbs of the mantissa of x */
precy = MPFR_PREC(y);
precx = (mpfr_prec_t) sx * GMP_NUMB_BITS;
sy = MPFR_LIMB_SIZE (y);
xp = PTR (x);
/* since mpf numbers are represented in base 2^GMP_NUMB_BITS,
we loose -EXP(y) % GMP_NUMB_BITS bits in the most significant limb */
sh = MPFR_GET_EXP(y) % GMP_NUMB_BITS;
sh = sh <= 0 ? - sh : GMP_NUMB_BITS - sh;
MPFR_ASSERTD (sh >= 0);
if (precy + sh <= precx) /* we can copy directly */
{
mp_size_t ds;
MPFR_ASSERTN (sx >= sy);
ds = sx - sy;
if (sh != 0)
{
mp_limb_t out;
out = mpn_rshift (xp + ds, MPFR_MANT(y), sy, sh);
MPFR_ASSERTN (ds > 0 || out == 0);
if (ds > 0)
xp[--ds] = out;
}
else
MPN_COPY (xp + ds, MPFR_MANT (y), sy);
if (ds > 0)
MPN_ZERO (xp, ds);
EXP(x) = (MPFR_GET_EXP(y) + sh) / GMP_NUMB_BITS;
inex = 0;
}
else /* we have to round to precx - sh bits */
{
mpfr_t z;
mp_size_t sz;
/* Recall that precx = (mpfr_prec_t) sx * GMP_NUMB_BITS, thus removing
sh bits (sh < GMP_NUMB_BITSS) won't reduce the number of limbs. */
mpfr_init2 (z, precx - sh);
sz = MPFR_LIMB_SIZE (z);
MPFR_ASSERTN (sx == sz);
inex = mpfr_set (z, y, rnd_mode);
/* warning, sh may change due to rounding, but then z is a power of two,
thus we can safely ignore its last bit which is 0 */
sh = MPFR_GET_EXP(z) % GMP_NUMB_BITS;
sh = sh <= 0 ? - sh : GMP_NUMB_BITS - sh;
MPFR_ASSERTD (sh >= 0);
if (sh != 0)
{
mp_limb_t out;
out = mpn_rshift (xp, MPFR_MANT(z), sz, sh);
/* If sh hasn't changed, it is the number of the non-significant
bits in the lowest limb of z. Therefore out == 0. */
MPFR_ASSERTD (out == 0); (void) out; /* avoid a warning */
}
else
MPN_COPY (xp, MPFR_MANT(z), sz);
EXP(x) = (MPFR_GET_EXP(z) + sh) / GMP_NUMB_BITS;
mpfr_clear (z);
}
/* set size and sign */
SIZ(x) = (MPFR_FROM_SIGN_TO_INT(MPFR_SIGN(y)) < 0) ? -sx : sx;
return inex;
}
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