niceSOFT/mpfr | Gitverse

src/div_2si.c
61 строка2 KB
Vincent Lefèvre
03 янв 2018, 13:53
03 янв 2018, 13:532fce388
/* mpfr_div_2si -- divide a floating-point number by a power of two

Copyright 1999, 2001-2018 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
http://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"

MPFR_HOT_FUNCTION_ATTR int
mpfr_div_2si (mpfr_ptr y, mpfr_srcptr x, long int n, mpfr_rnd_t rnd_mode)
{
  int inexact;

  MPFR_LOG_FUNC
    (("x[%Pu]=%.*Rg n=%ld rnd=%d",
      mpfr_get_prec(x), mpfr_log_prec, x, n, rnd_mode),
     ("y[%Pu]=%.*Rg inexact=%d",
      mpfr_get_prec(y), mpfr_log_prec, y, inexact));

  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x)))
    return mpfr_set (y, x, rnd_mode);
  else
    {
      mpfr_exp_t exp = MPFR_GET_EXP (x);
      MPFR_SETRAW (inexact, y, x, exp, rnd_mode);
      if (MPFR_UNLIKELY( n > 0 && (__gmpfr_emin > MPFR_EMAX_MAX - n ||
                                   exp < __gmpfr_emin + n)) )
        {
          if (rnd_mode == MPFR_RNDN &&
              (__gmpfr_emin > MPFR_EMAX_MAX - (n - 1) ||
               exp < __gmpfr_emin + (n - 1) ||
               ((MPFR_IS_NEG (y) ? inexact <= 0 : inexact >= 0) &&
                mpfr_powerof2_raw (y))))
            rnd_mode = MPFR_RNDZ;
          return mpfr_underflow (y, rnd_mode, MPFR_SIGN(y));
        }
      else if (MPFR_UNLIKELY(n <= 0 && (__gmpfr_emax < MPFR_EMIN_MIN - n ||
                                       exp > __gmpfr_emax + n)) )
        return mpfr_overflow (y, rnd_mode, MPFR_SIGN(y));

      MPFR_SET_EXP (y, exp - n);
    }

  MPFR_RET (inexact);
}