1 /* mpfr_get_sj -- convert a MPFR number to a huge machine signed integer
2
3 Copyright 2004, 2006-2023 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_INTMAX_H
24 #include "mpfr-impl.h"
25
26 #ifdef _MPFR_H_HAVE_INTMAX_T
27
28 intmax_t
mpfr_get_sj(mpfr_srcptr f,mpfr_rnd_t rnd)29 mpfr_get_sj (mpfr_srcptr f, mpfr_rnd_t rnd)
30 {
31 intmax_t r;
32 mpfr_prec_t prec;
33 mpfr_t x;
34 MPFR_SAVE_EXPO_DECL (expo);
35
36 if (MPFR_UNLIKELY (!mpfr_fits_intmax_p (f, rnd)))
37 {
38 MPFR_SET_ERANGEFLAG ();
39 return MPFR_IS_NAN (f) ? 0 :
40 MPFR_IS_NEG (f) ? INTMAX_MIN : INTMAX_MAX;
41 }
42
43 if (MPFR_IS_ZERO (f))
44 return (intmax_t) 0;
45
46 /* Determine the precision of intmax_t. |INTMAX_MIN| may have one
47 more bit as an integer, but in this case, this is a power of 2,
48 thus fits in a precision-prec floating-point number. */
49 for (r = INTMAX_MAX, prec = 0; r != 0; r /= 2, prec++)
50 { }
51
52 MPFR_ASSERTD (r == 0);
53
54 MPFR_SAVE_EXPO_MARK (expo);
55
56 mpfr_init2 (x, prec);
57 mpfr_rint (x, f, rnd);
58 MPFR_ASSERTN (MPFR_IS_FP (x));
59
60 /* The flags from mpfr_rint are the wanted ones. In particular,
61 it sets the inexact flag when necessary. */
62 MPFR_SAVE_EXPO_UPDATE_FLAGS (expo, __gmpfr_flags);
63
64 if (MPFR_NOTZERO (x))
65 {
66 mp_limb_t *xp;
67 int sh; /* An int should be sufficient in this context. */
68
69 xp = MPFR_MANT (x);
70 sh = MPFR_GET_EXP (x);
71 MPFR_ASSERTN ((mpfr_prec_t) sh <= prec + 1);
72 if (INTMAX_MIN + INTMAX_MAX != 0
73 && MPFR_UNLIKELY ((mpfr_prec_t) sh > prec))
74 {
75 /* 2's complement and x <= INTMAX_MIN: in the case mp_limb_t
76 has the same size as intmax_t, we cannot use the code in
77 the for loop since the operations would be performed in
78 unsigned arithmetic. */
79 MPFR_ASSERTD (MPFR_IS_NEG (x) && mpfr_powerof2_raw (x));
80 r = INTMAX_MIN;
81 }
82 /* sh is the number of bits that remain to be considered in {xp, xn} */
83 else
84 {
85 #ifdef MPFR_INTMAX_WITHIN_LIMB
86 MPFR_ASSERTD (sh > 0 && sh < GMP_NUMB_BITS);
87 r = xp[0] >> (GMP_NUMB_BITS - sh);
88 #else
89 int n;
90
91 /* Note: testing the condition sh > 0 is necessary to avoid
92 an undefined behavior on xp[n] >> S when S >= GMP_NUMB_BITS
93 (even though xp[n] == 0 in such a case). This can happen if
94 sizeof(mp_limb_t) < sizeof(intmax_t) and |x| is small enough
95 because of the trailing bits due to its normalization. */
96 for (n = MPFR_LIMB_SIZE (x) - 1; n >= 0 && sh > 0; n--)
97 {
98 sh -= GMP_NUMB_BITS;
99 /* Note the concerning the casts below:
100 When sh >= 0, the cast must be performed before the shift
101 for the case sizeof(intmax_t) > sizeof(mp_limb_t).
102 When sh < 0, the cast must be performed after the shift
103 for the case sizeof(intmax_t) == sizeof(mp_limb_t), as
104 mp_limb_t is unsigned, therefore not representable as an
105 intmax_t when the MSB is 1 (this is the case here). */
106 MPFR_ASSERTD (-sh < GMP_NUMB_BITS);
107 /* each limb should be shifted by sh bits to the left if sh>=0,
108 and by sh bits to the right if sh < 0 */
109 r += sh >= 0
110 ? (intmax_t) xp[n] << sh
111 : (intmax_t) (xp[n] >> (-sh));
112 }
113 #endif
114 if (MPFR_IS_NEG(x))
115 r = -r;
116 }
117 }
118
119 mpfr_clear (x);
120
121 MPFR_SAVE_EXPO_FREE (expo);
122
123 return r;
124 }
125
126 #endif
127