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/* mpfr_get_si -- convert a floating-point number to a signed long.
Copyright 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
This file is part of the MPFR Library.
The 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 2.1 of the License, or (at your
option) any later version.
The 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 MPFR Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
MA 02110-1301, USA. */
#include <limits.h>
#include "mpfr-impl.h"
long
mpfr_get_si (mpfr_srcptr f, mp_rnd_t rnd)
{
mp_prec_t prec;
long s;
mpfr_t x;
if (MPFR_UNLIKELY (!mpfr_fits_slong_p (f, rnd)))
{
MPFR_SET_ERANGE ();
return MPFR_IS_NEG (f) ? LONG_MIN : LONG_MAX;
}
else if (MPFR_UNLIKELY (MPFR_IS_ZERO (f)))
return (long) 0;
/* determine prec of long */
for (s = LONG_MIN, prec = 0; s != 0; s /= 2, prec ++);
/* first round to prec bits */
mpfr_init2 (x, prec);
mpfr_rint (x, f, rnd);
/* 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;
mp_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] >> (BITS_PER_MP_LIMB - exp);
s = MPFR_SIGN(f) > 0 ? a : a <= LONG_MAX ? - (long) a : LONG_MIN;
}
mpfr_clear (x);
return s;
}
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