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/* mpfr_fits_*_p -- test whether an mpfr fits a C signed type.
Copyright 2003-2020 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"
/* The original version of this file came from GMP's mpf/fits_s.h;
it has been adapted for MPFR. In particular, the result can be
rounded away from zero. */
int
FUNCTION (mpfr_srcptr f, mpfr_rnd_t rnd)
{
mpfr_flags_t saved_flags;
mpfr_exp_t e;
int prec;
mpfr_t x;
int neg;
int res;
if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (f)))
/* Zero always fit */
return MPFR_IS_ZERO (f) ? 1 : 0;
/* now it fits if either
(a) MINIMUM <= f <= MAXIMUM
(b) or MINIMUM <= round(f, prec(slong), rnd) <= MAXIMUM */
e = MPFR_GET_EXP (f);
if (e < 1)
return 1; /* |f| < 1: always fits */
neg = MPFR_IS_NEG (f);
/* let EXTREMUM be MAXIMUM if f > 0, and MINIMUM if f < 0 */
/* first compute prec(EXTREMUM), this could be done at configure time,
but the result can depend on neg (the loop is moved inside the "if"
to give the compiler a better chance to compute prec statically) */
if (neg)
{
unsigned TYPE s;
/* In C89, the division on negative integers isn't well-defined. */
s = SAFE_ABS (unsigned TYPE, MINIMUM);
for (prec = 0; s != 0; s /= 2, prec ++);
}
else
{
TYPE s;
s = MAXIMUM;
for (prec = 0; s != 0; s /= 2, prec ++);
}
/* EXTREMUM needs prec bits, i.e. 2^(prec-1) <= |EXTREMUM| < 2^prec */
/* if e <= prec - 1, then f < 2^(prec-1) <= |EXTREMUM| */
if (e <= prec - 1)
return 1;
/* if e >= prec + 1, then f >= 2^prec > |EXTREMUM| */
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 RNDF, it suffices to check it fits when rounded away from zero */
mpfr_set (x, f, (rnd == MPFR_RNDF) ? MPFR_RNDA : rnd);
/* 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 = neg ? (mpfr_cmp_si (x, MINIMUM) >= 0) : (MPFR_EXP (x) == e);
mpfr_clear (x);
__gmpfr_flags = saved_flags;
return res;
}
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