1/* mpfr_set_f -- set a MPFR number from a GNU MPF number
2
3Copyright 1999-2023 Free Software Foundation, Inc.
4Contributed by the AriC and Caramba projects, INRIA.
5
6This file is part of the GNU MPFR Library.
7
8The GNU MPFR Library is free software; you can redistribute it and/or modify
9it under the terms of the GNU Lesser General Public License as published by
10the Free Software Foundation; either version 3 of the License, or (at your
11option) any later version.
12
13The GNU MPFR Library is distributed in the hope that it will be useful, but
14WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
15or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
16License for more details.
17
18You should have received a copy of the GNU Lesser General Public License
19along with the GNU MPFR Library; see the file COPYING.LESSER.  If not, see
20https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
2151 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
28int
29mpfr_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