/* mpfr_get_si -- convert a floating-point number to a signed long.
Copyright 2003-2019 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
https://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"
long
mpfr_get_si (mpfr_srcptr f, mpfr_rnd_t rnd)
{
mpfr_prec_t prec;
long s;
mpfr_t x;
MPFR_SAVE_EXPO_DECL (expo);
if (MPFR_UNLIKELY (!mpfr_fits_slong_p (f, rnd)))
{
MPFR_SET_ERANGEFLAG ();
return MPFR_IS_NAN (f) ? 0 :
MPFR_IS_NEG (f) ? LONG_MIN : LONG_MAX;
}
if (MPFR_IS_ZERO (f))
return (long) 0;
/* Determine the precision of long. |LONG_MIN| may have one more bit
as an integer, but in this case, this is a power of 2, thus fits
in a precision-prec floating-point number. */
for (s = LONG_MAX, prec = 0; s != 0; s /= 2, prec++)
{ }
MPFR_SAVE_EXPO_MARK (expo);
/* first round to prec bits */
mpfr_init2 (x, prec);
mpfr_rint (x, f, rnd);
/* The flags from mpfr_rint are the wanted ones. In particular,
it sets the inexact flag when necessary. */
MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, __gmpfr_flags);
/* warning: if x=0, taking its exponent is illegal */
if (MPFR_UNLIKELY (MPFR_IS_ZERO(x)))
s = 0;
else
{
mp_limb_t a;
mp_size_t n;
mpfr_exp_t exp;
/* now the result is in the most significant limb of x */
exp = MPFR_GET_EXP (x); /* since |x| >= 1, exp >= 1 */
n = MPFR_LIMB_SIZE(x);
a = MPFR_MANT(x)[n - 1] >> (GMP_NUMB_BITS - exp);
s = MPFR_IS_POS (f) ? a : a <= LONG_MAX ? - (long) a : LONG_MIN;
}
mpfr_clear (x);
MPFR_SAVE_EXPO_FREE (expo);
return s;
}