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/* mpfr_fits_*_p -- test whether an mpfr fits a C unsigned type.
Copyright 2003-2021 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"
int
FUNCTION (mpfr_srcptr f, mpfr_rnd_t rnd)
{
mpfr_flags_t saved_flags;
mpfr_exp_t e;
int prec;
TYPE s;
mpfr_t x;
int res;
if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (f)))
return MPFR_IS_ZERO (f) ? 1 : 0; /* Zero always fits */
e = MPFR_GET_EXP (f);
if (MPFR_IS_NEG (f))
return e >= 1 ? 0 /* f <= -1 does not fit */
: rnd != MPFR_RNDN ? MPFR_IS_LIKE_RNDU (rnd, -1) /* directed mode */
: e < 0 ? 1 /* f > -1/2 fits in MPFR_RNDN */
: mpfr_powerof2_raw(f); /* -1/2 fits, -1 < f < -1/2 don't */
/* Now it fits if
(a) f <= MAXIMUM
(b) round(f, prec(slong), rnd) <= MAXIMUM */
/* first compute prec(MAXIMUM); fits in an int */
for (s = MAXIMUM, prec = 0; s != 0; s /= 2, prec ++);
/* MAXIMUM needs prec bits, i.e. MAXIMUM = 2^prec - 1 */
/* if e <= prec - 1, then f < 2^(prec-1) < MAXIMUM */
if (e <= prec - 1)
return 1;
/* if e >= prec + 1, then f >= 2^prec > MAXIMUM */
if (e >= prec + 1)
return 0;
MPFR_ASSERTD (e == prec);
/* hard case: first round to prec bits, then check */
saved_flags = __gmpfr_flags;
mpfr_init2 (x, prec);
/* For MPFR_RNDF, if f > 0 fits with RNDU, it will also fit with RNDD. */
mpfr_set (x, f, (rnd != MPFR_RNDF) ? rnd : MPFR_RNDU);
/* Warning! Due to the rounding, x can be an infinity. Here we use
the fact that singular numbers have a special exponent field,
thus well-defined and different from e, in which case this means
that the number does not fit. That's why we use MPFR_EXP, not
MPFR_GET_EXP. */
res = MPFR_EXP (x) == e;
mpfr_clear (x);
__gmpfr_flags = saved_flags;
return res;
}
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