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      1 /* mpfr_set_f -- set a MPFR number from a GNU MPF number
      2 
      3 Copyright 1999-2023 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 #define MPFR_NEED_LONGLONG_H
     24 #define MPFR_NEED_MPF_INTERNALS
     25 #include "mpfr-impl.h"
     26 
     27 #ifndef MPFR_USE_MINI_GMP
     28 int
     29 mpfr_set_f (mpfr_ptr y, mpf_srcptr x, mpfr_rnd_t rnd_mode)
     30 {
     31   mp_limb_t *my, *mx, *tmp;
     32   int cnt;
     33   mp_size_t sx, sy;
     34   int inexact, carry = 0;
     35   MPFR_TMP_DECL(marker);
     36 
     37   sx = ABSIZ(x); /* number of limbs of the mantissa of x */
     38 
     39   if (sx == 0) /* x is zero */
     40     {
     41       MPFR_SET_ZERO(y);
     42       MPFR_SET_POS(y);
     43       return 0; /* 0 is exact */
     44     }
     45 
     46   if (SIZ(x) * MPFR_FROM_SIGN_TO_INT(MPFR_SIGN(y)) < 0)
     47     MPFR_CHANGE_SIGN (y);
     48 
     49   sy = MPFR_LIMB_SIZE (y);
     50   my = MPFR_MANT(y);
     51   mx = PTR(x);
     52 
     53   count_leading_zeros(cnt, mx[sx - 1]);
     54 
     55   if (sy <= sx) /* we may have to round even when sy = sx */
     56     {
     57       mpfr_prec_t xprec = (mpfr_prec_t) sx * GMP_NUMB_BITS;
     58 
     59       MPFR_TMP_MARK(marker);
     60       tmp = MPFR_TMP_LIMBS_ALLOC (sx);
     61       if (cnt)
     62         mpn_lshift (tmp, mx, sx, cnt);
     63       else
     64         /* FIXME: we may avoid the copy here, and directly call mpfr_round_raw
     65            on mx instead of tmp */
     66         MPN_COPY (tmp, mx, sx);
     67       carry = mpfr_round_raw (my, tmp, xprec, (SIZ(x) < 0), MPFR_PREC(y),
     68                               rnd_mode, &inexact);
     69       if (MPFR_UNLIKELY(carry)) /* result is a power of two */
     70         my[sy - 1] = MPFR_LIMB_HIGHBIT;
     71       MPFR_TMP_FREE(marker);
     72     }
     73   else
     74     {
     75       if (cnt)
     76         mpn_lshift (my + sy - sx, mx, sx, cnt);
     77       else
     78         MPN_COPY (my + sy - sx, mx, sx);
     79       MPN_ZERO(my, sy - sx);
     80       /* no rounding necessary, since y has a larger mantissa */
     81       inexact = 0;
     82     }
     83 
     84   /* warning: EXP(x) * GMP_NUMB_BITS may exceed the maximal exponent */
     85   if (EXP(x) > 1 + (__gmpfr_emax - 1) / GMP_NUMB_BITS)
     86     {
     87       /* EXP(x) >= 2 + floor((__gmpfr_emax-1)/GMP_NUMB_BITS)
     88          EXP(x) >= 2 + (__gmpfr_emax - GMP_NUMB_BITS) / GMP_NUMB_BITS
     89                 >= 1 + __gmpfr_emax / GMP_NUMB_BITS
     90          EXP(x) * GMP_NUMB_BITS >= __gmpfr_emax + GMP_NUMB_BITS
     91          Since 0 <= cnt <= GMP_NUMB_BITS-1, and 0 <= carry <= 1,
     92          we have then EXP(x) * GMP_NUMB_BITS - cnt + carry > __gmpfr_emax */
     93       return mpfr_overflow (y, rnd_mode, MPFR_SIGN (y));
     94     }
     95   else
     96     {
     97       /* Do not use MPFR_SET_EXP as the exponent may be out of range. */
     98       MPFR_EXP (y) = EXP (x) * GMP_NUMB_BITS - cnt + carry;
     99     }
    100 
    101   return mpfr_check_range (y, inexact, rnd_mode);
    102 }
    103 #endif
    104