/* mpfr_get_si -- convert a floating-point number to a signed long.

Copyright 2003, 2004 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 Place, 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;
}