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/* mpfr_get_sj -- convert a MPFR number to a huge machine signed integer
Copyright 2004, 2006-2015 Free Software Foundation, Inc.
Contributed by the AriC and Caramel 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. */
#ifdef HAVE_CONFIG_H
# include "config.h" /* for a build within gmp */
#endif
#include "mpfr-intmax.h"
#include "mpfr-impl.h"
#ifdef _MPFR_H_HAVE_INTMAX_T
intmax_t
mpfr_get_sj (mpfr_srcptr f, mpfr_rnd_t rnd)
{
intmax_t r;
mpfr_prec_t prec;
mpfr_t x;
if (MPFR_UNLIKELY (!mpfr_fits_intmax_p (f, rnd)))
{
MPFR_SET_ERANGEFLAG ();
return MPFR_IS_NAN (f) ? 0 :
MPFR_IS_NEG (f) ? MPFR_INTMAX_MIN : MPFR_INTMAX_MAX;
}
if (MPFR_IS_ZERO (f))
return (intmax_t) 0;
/* determine the precision of intmax_t */
for (r = MPFR_INTMAX_MIN, prec = 0; r != 0; r /= 2, prec++)
{ }
/* Note: though INTMAX_MAX would have been sufficient for the conversion,
we chose INTMAX_MIN so that INTMAX_MIN - 1 is always representable in
precision prec; this is useful to detect overflows in MPFR_RNDZ (will
be needed later). */
/* Now, r = 0. */
mpfr_init2 (x, prec);
mpfr_rint (x, f, rnd);
MPFR_ASSERTN (MPFR_IS_FP (x));
if (MPFR_NOTZERO (x))
{
mp_limb_t *xp;
int sh, n; /* An int should be sufficient in this context. */
xp = MPFR_MANT (x);
sh = MPFR_GET_EXP (x);
MPFR_ASSERTN ((mpfr_prec_t) sh <= prec);
if (MPFR_INTMAX_MIN + MPFR_INTMAX_MAX != 0
&& MPFR_UNLIKELY ((mpfr_prec_t) sh == prec))
{
/* 2's complement and x <= INTMAX_MIN: in the case mp_limb_t
has the same size as intmax_t, we cannot use the code in
the for loop since the operations would be performed in
unsigned arithmetic. */
MPFR_ASSERTN (MPFR_IS_NEG (x) && (mpfr_powerof2_raw (x)));
r = MPFR_INTMAX_MIN;
}
else if (MPFR_IS_POS (x))
{
/* Note: testing the condition sh >= 0 is necessary to avoid
an undefined behavior on xp[n] >> S when S >= GMP_NUMB_BITS
(even though xp[n] == 0 in such a case). This can happen if
sizeof(mp_limb_t) < sizeof(intmax_t) and |x| is small enough
because of the trailing bits due to its normalization. */
for (n = MPFR_LIMB_SIZE (x) - 1; n >= 0 && sh >= 0; n--)
{
sh -= GMP_NUMB_BITS;
/* Note the concerning the casts below:
When sh >= 0, the cast must be performed before the shift
for the case sizeof(intmax_t) > sizeof(mp_limb_t).
When sh < 0, the cast must be performed after the shift
for the case sizeof(intmax_t) == sizeof(mp_limb_t), as
mp_limb_t is unsigned, therefore not representable as an
intmax_t when the MSB is 1 (this is the case here). */
MPFR_ASSERTD (sh < GMP_NUMB_BITS && -sh < GMP_NUMB_BITS);
r += (sh >= 0
? (intmax_t) xp[n] << sh
: (intmax_t) (xp[n] >> (-sh)));
}
}
else
{
/* See the comments for the case x positive. */
for (n = MPFR_LIMB_SIZE (x) - 1; n >= 0 && sh >= 0; n--)
{
sh -= GMP_NUMB_BITS;
MPFR_ASSERTD (sh < GMP_NUMB_BITS && -sh < GMP_NUMB_BITS);
r -= (sh >= 0
? (intmax_t) xp[n] << sh
: (intmax_t) (xp[n] >> (-sh)));
}
}
}
mpfr_clear (x);
return r;
}
#endif
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