1  /* mpfr_ui_div -- divide a machine integer by a floating-point number
       2  
       3  Copyright 2000-2023 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  
      24  #define MPFR_NEED_LONGLONG_H
      25  #include "mpfr-impl.h"
      26  
      27  int
      28  mpfr_ui_div (mpfr_ptr y, unsigned long int u, mpfr_srcptr x, mpfr_rnd_t rnd_mode)
      29  {
      30    MPFR_LOG_FUNC
      31      (("u=%lu x[%Pd]=%.*Rg rnd=%d",
      32        u, mpfr_get_prec(x), mpfr_log_prec, x, rnd_mode),
      33       ("y[%Pd]=%.*Rg", mpfr_get_prec(y), mpfr_log_prec, y));
      34  
      35    if (MPFR_UNLIKELY(MPFR_IS_SINGULAR(x)))
      36      {
      37        if (MPFR_IS_NAN(x))
      38          {
      39            MPFR_SET_NAN(y);
      40            MPFR_RET_NAN;
      41          }
      42        else if (MPFR_IS_INF(x)) /* u/Inf = 0 */
      43          {
      44            MPFR_SET_ZERO(y);
      45            MPFR_SET_SAME_SIGN(y,x);
      46            MPFR_RET(0);
      47          }
      48        else /* u / 0 */
      49          {
      50            MPFR_ASSERTD(MPFR_IS_ZERO(x));
      51            if (u)
      52              {
      53                /* u > 0, so y = sign(x) * Inf */
      54                MPFR_SET_SAME_SIGN(y, x);
      55                MPFR_SET_INF(y);
      56                MPFR_SET_DIVBY0 ();
      57                MPFR_RET(0);
      58              }
      59            else
      60              {
      61                /* 0 / 0 */
      62                MPFR_SET_NAN(y);
      63                MPFR_RET_NAN;
      64              }
      65          }
      66      }
      67    else if (MPFR_LIKELY(u != 0))
      68      {
      69        int inex;
      70        MPFR_SAVE_EXPO_DECL (expo);
      71  
      72        /* Optimization note: Exponent save/restore operations may be
      73           removed if mpfr_div works even when uu is out-of-range. */
      74        MPFR_SAVE_EXPO_MARK (expo);
      75  
      76  #ifdef MPFR_LONG_WITHIN_LIMB
      77        {
      78          mpfr_t uu;
      79          mp_limb_t up[1];
      80          int cnt;
      81  
      82          MPFR_TMP_INIT1(up, uu, GMP_NUMB_BITS);
      83          MPFR_ASSERTN(u == (mp_limb_t) u);
      84          count_leading_zeros(cnt, (mp_limb_t) u);
      85          up[0] = (mp_limb_t) u << cnt;
      86  
      87          MPFR_SET_EXP (uu, GMP_NUMB_BITS - cnt);
      88          inex = mpfr_div (y, uu, x, rnd_mode);
      89        }
      90  #else
      91        {
      92        mpfr_t uu;
      93  
      94        mpfr_init2 (uu, sizeof (unsigned long) * CHAR_BIT);
      95        mpfr_set_ui (uu, u, MPFR_RNDZ);
      96        inex = mpfr_div (y, uu, x, rnd_mode);
      97        mpfr_clear (uu);
      98        }
      99  #endif
     100  
     101        MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, __gmpfr_flags);
     102        MPFR_SAVE_EXPO_FREE (expo);
     103        return mpfr_check_range (y, inex, rnd_mode);
     104      }
     105    else /* u = 0, and x != 0 */
     106      {
     107        MPFR_SET_ZERO(y);         /* if u=0, then set y to 0 */
     108        MPFR_SET_SAME_SIGN(y, x); /* u considered as +0: sign(+0/x) = sign(x) */
     109        MPFR_RET(0);
     110      }
     111  }