1/* mpfr_get_si -- convert a floating-point number to a signed long.
2
3Copyright 2003-2023 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#include "mpfr-impl.h"
24
25long
26mpfr_get_si (mpfr_srcptr f, mpfr_rnd_t rnd)
27{
28  mpfr_prec_t prec;
29  long s;
30  mpfr_t x;
31  MPFR_SAVE_EXPO_DECL (expo);
32
33  if (MPFR_UNLIKELY (!mpfr_fits_slong_p (f, rnd)))
34    {
35      MPFR_SET_ERANGEFLAG ();
36      return MPFR_IS_NAN (f) ? 0 :
37        MPFR_IS_NEG (f) ? LONG_MIN : LONG_MAX;
38    }
39
40  if (MPFR_IS_ZERO (f))
41    return (long) 0;
42
43  /* Determine the precision of long. |LONG_MIN| may have one more bit
44     as an integer, but in this case, this is a power of 2, thus fits
45     in a precision-prec floating-point number. */
46  for (s = LONG_MAX, prec = 0; s != 0; s /= 2, prec++)
47    { }
48
49  MPFR_SAVE_EXPO_MARK (expo);
50
51  /* first round to prec bits */
52  mpfr_init2 (x, prec);
53  mpfr_rint (x, f, rnd);
54
55  /* The flags from mpfr_rint are the wanted ones. In particular,
56     it sets the inexact flag when necessary. */
57  MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, __gmpfr_flags);
58
59  /* warning: if x=0, taking its exponent is illegal */
60  if (MPFR_IS_ZERO (x))
61    s = 0;
62  else
63    {
64      unsigned long u = 0;
65      mp_size_t n;
66      mpfr_exp_t exp;
67
68      exp = MPFR_GET_EXP (x);
69      MPFR_ASSERTD (exp >= 1); /* since |x| >= 1 */
70      n = MPFR_LIMB_SIZE (x);
71#ifdef MPFR_LONG_WITHIN_LIMB
72      MPFR_ASSERTD (exp <= GMP_NUMB_BITS);
73#else
74      while (exp > GMP_NUMB_BITS)
75        {
76          MPFR_ASSERTD (n > 0);
77          u += (unsigned long) MPFR_MANT(x)[n - 1] << (exp - GMP_NUMB_BITS);
78          n--;
79          exp -= GMP_NUMB_BITS;
80        }
81#endif
82      MPFR_ASSERTD (n > 0);
83      u += MPFR_MANT(x)[n - 1] >> (GMP_NUMB_BITS - exp);
84      s = MPFR_IS_POS (f) ? u : u <= LONG_MAX ? - (long) u : LONG_MIN;
85    }
86
87  mpfr_clear (x);
88
89  MPFR_SAVE_EXPO_FREE (expo);
90
91  return s;
92}
93