1 /* mpfr_get_si -- convert a floating-point number to a signed long.
2
3 Copyright 2003-2023 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 long
mpfr_get_si(mpfr_srcptr f,mpfr_rnd_t rnd)26 mpfr_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