1  /* mpfr_get_ui -- convert a floating-point number to an unsigned long.
       2  
       3  Copyright 2003-2004, 2006-2023 Free Software Foundation, Inc.
       4  Contributed by the AriC and Caramba projects, INRIA.
       5  
       6  This file is part of the GNU MPFR Library.
       7  
       8  The GNU MPFR Library is free software; you can redistribute it and/or modify
       9  it under the terms of the GNU Lesser General Public License as published by
      10  the Free Software Foundation; either version 3 of the License, or (at your
      11  option) any later version.
      12  
      13  The GNU MPFR Library is distributed in the hope that it will be useful, but
      14  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
      15  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
      16  License for more details.
      17  
      18  You should have received a copy of the GNU Lesser General Public License
      19  along with the GNU MPFR Library; see the file COPYING.LESSER.  If not, see
      20  https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
      21  51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
      22  
      23  #include "mpfr-impl.h"
      24  
      25  unsigned long
      26  mpfr_get_ui (mpfr_srcptr f, mpfr_rnd_t rnd)
      27  {
      28    mpfr_prec_t prec;
      29    unsigned long s;
      30    mpfr_t x;
      31    mp_size_t n;
      32    mpfr_exp_t exp;
      33    MPFR_SAVE_EXPO_DECL (expo);
      34  
      35    if (MPFR_UNLIKELY (!mpfr_fits_ulong_p (f, rnd)))
      36      {
      37        MPFR_SET_ERANGEFLAG ();
      38        return MPFR_IS_NAN (f) || MPFR_IS_NEG (f) ?
      39          (unsigned long) 0 : ULONG_MAX;
      40      }
      41  
      42    if (MPFR_IS_ZERO (f))
      43      return (unsigned long) 0;
      44  
      45    for (s = ULONG_MAX, prec = 0; s != 0; s /= 2, prec ++)
      46      { }
      47  
      48    MPFR_SAVE_EXPO_MARK (expo);
      49  
      50    /* first round to prec bits */
      51    mpfr_init2 (x, prec);
      52    mpfr_rint (x, f, rnd);
      53  
      54    /* The flags from mpfr_rint are the wanted ones. In particular,
      55       it sets the inexact flag when necessary. */
      56    MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, __gmpfr_flags);
      57  
      58    /* warning: if x=0, taking its exponent is illegal */
      59    if (MPFR_NOTZERO (x))
      60      {
      61        exp = MPFR_GET_EXP (x);
      62        MPFR_ASSERTD (exp >= 1); /* since |x| >= 1 */
      63        n = MPFR_LIMB_SIZE (x);
      64  #ifdef MPFR_LONG_WITHIN_LIMB
      65        MPFR_ASSERTD (exp <= GMP_NUMB_BITS);
      66  #else
      67        while (exp > GMP_NUMB_BITS)
      68          {
      69            MPFR_ASSERTD (n > 0);
      70            s += (unsigned long) MPFR_MANT(x)[n - 1] << (exp - GMP_NUMB_BITS);
      71            n--;
      72            exp -= GMP_NUMB_BITS;
      73          }
      74  #endif
      75        MPFR_ASSERTD (n > 0);
      76        s += MPFR_MANT(x)[n - 1] >> (GMP_NUMB_BITS - exp);
      77      }
      78  
      79    mpfr_clear (x);
      80  
      81    MPFR_SAVE_EXPO_FREE (expo);
      82  
      83    return s;
      84  }