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/* mpfr_get_sj -- convert a MPFR number to a huge machine signed integer
Copyright 2004, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
Contributed by the Arenaire 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
/* The ISO C99 standard specifies that in C++ implementations the
INTMAX_MAX, ... macros should only be defined if explicitly requested. */
#if defined __cplusplus
# define __STDC_LIMIT_MACROS
# define __STDC_CONSTANT_MACROS
#endif
#if HAVE_INTTYPES_H
# include <inttypes.h>
#endif
#if HAVE_STDINT_H
# include <stdint.h>
#endif
#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_ERANGE ();
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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