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/* mpfr_get_f -- convert a MPFR number to a GNU MPF number
Copyright 2005, 2006 Free Software Foundation, Inc.
This file is part of the MPFR Library.
The 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 2.1 of the License, or (at your
option) any later version.
The 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 MPFR Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 51 Franklin Place, Fifth Floor, Boston,
MA 02110-1301, USA. */
#include "mpfr-impl.h"
/* return value is 0 iff no error occurred in the conversion
(1 for NaN, +Inf, -Inf that have no equivalent in mpf)
*/
int
mpfr_get_f (mpf_ptr x, mpfr_srcptr y, mp_rnd_t rnd_mode)
{
mp_size_t sx, sy;
mp_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 /* NaN or Inf */
return 1;
}
sx = PREC(x); /* number of limbs of the mantissa of x */
precy = MPFR_PREC(y);
precx = (mp_prec_t) sx * BITS_PER_MP_LIMB;
sy = MPFR_LIMB_SIZE (y);
xp = PTR (x);
/* since mpf numbers are represented in base 2^BITS_PER_MP_LIMB,
we loose -EXP(y) % BITS_PER_MP_LIMB bits in the most significant limb */
sh = MPFR_GET_EXP(y) % BITS_PER_MP_LIMB;
sh = sh <= 0 ? - sh : BITS_PER_MP_LIMB - 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) / BITS_PER_MP_LIMB;
}
else /* we have to round to precx - sh bits */
{
mpfr_t z;
mp_size_t sz, ds;
/* Recall that precx = (mp_prec_t) sx * BITS_PER_MP_LIMB */
mpfr_init2 (z, precx - sh);
sz = MPFR_LIMB_SIZE (z);
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) % BITS_PER_MP_LIMB;
sh = sh <= 0 ? - sh : BITS_PER_MP_LIMB - sh;
MPFR_ASSERTD (sx >= sz);
ds = sx - sz;
MPFR_ASSERTD (sh >= 0 && ds <= 1);
if (sh != 0)
{
mp_limb_t out;
out = mpn_rshift (xp + ds, 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);
}
else
MPN_COPY (xp + ds, MPFR_MANT(z), sz);
if (ds != 0)
xp[0] = 0;
EXP(x) = (MPFR_GET_EXP(z) + sh) / BITS_PER_MP_LIMB;
mpfr_clear (z);
}
/* set size and sign */
SIZ(x) = (MPFR_FROM_SIGN_TO_INT(MPFR_SIGN(y)) < 0) ? -sx : sx;
return 0;
}
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