1 /* mpfr_get_sj -- convert a MPFR number to a huge machine signed integer
2
3 Copyright 2004, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
4 Contributed by the AriC and Caramel 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 http://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 #ifdef HAVE_CONFIG_H
24 # include "config.h" /* for a build within gmp */
25 #endif
26
27 #include "mpfr-intmax.h"
28 #include "mpfr-impl.h"
29
30 #ifdef _MPFR_H_HAVE_INTMAX_T
31
32 intmax_t
mpfr_get_sj(mpfr_srcptr f,mpfr_rnd_t rnd)33 mpfr_get_sj (mpfr_srcptr f, mpfr_rnd_t rnd)
34 {
35 intmax_t r;
36 mpfr_prec_t prec;
37 mpfr_t x;
38
39 if (MPFR_UNLIKELY (!mpfr_fits_intmax_p (f, rnd)))
40 {
41 MPFR_SET_ERANGE ();
42 return MPFR_IS_NAN (f) ? 0 :
43 MPFR_IS_NEG (f) ? MPFR_INTMAX_MIN : MPFR_INTMAX_MAX;
44 }
45
46 if (MPFR_IS_ZERO (f))
47 return (intmax_t) 0;
48
49 /* determine the precision of intmax_t */
50 for (r = MPFR_INTMAX_MIN, prec = 0; r != 0; r /= 2, prec++)
51 { }
52 /* Note: though INTMAX_MAX would have been sufficient for the conversion,
53 we chose INTMAX_MIN so that INTMAX_MIN - 1 is always representable in
54 precision prec; this is useful to detect overflows in MPFR_RNDZ (will
55 be needed later). */
56
57 /* Now, r = 0. */
58
59 mpfr_init2 (x, prec);
60 mpfr_rint (x, f, rnd);
61 MPFR_ASSERTN (MPFR_IS_FP (x));
62
63 if (MPFR_NOTZERO (x))
64 {
65 mp_limb_t *xp;
66 int sh, n; /* An int should be sufficient in this context. */
67
68 xp = MPFR_MANT (x);
69 sh = MPFR_GET_EXP (x);
70 MPFR_ASSERTN ((mpfr_prec_t) sh <= prec);
71 if (MPFR_INTMAX_MIN + MPFR_INTMAX_MAX != 0
72 && MPFR_UNLIKELY ((mpfr_prec_t) sh == prec))
73 {
74 /* 2's complement and x <= INTMAX_MIN: in the case mp_limb_t
75 has the same size as intmax_t, we cannot use the code in
76 the for loop since the operations would be performed in
77 unsigned arithmetic. */
78 MPFR_ASSERTN (MPFR_IS_NEG (x) && (mpfr_powerof2_raw (x)));
79 r = MPFR_INTMAX_MIN;
80 }
81 else if (MPFR_IS_POS (x))
82 {
83 /* Note: testing the condition sh >= 0 is necessary to avoid
84 an undefined behavior on xp[n] >> S when S >= GMP_NUMB_BITS
85 (even though xp[n] == 0 in such a case). This can happen if
86 sizeof(mp_limb_t) < sizeof(intmax_t) and |x| is small enough
87 because of the trailing bits due to its normalization. */
88 for (n = MPFR_LIMB_SIZE (x) - 1; n >= 0 && sh >= 0; n--)
89 {
90 sh -= GMP_NUMB_BITS;
91 /* Note the concerning the casts below:
92 When sh >= 0, the cast must be performed before the shift
93 for the case sizeof(intmax_t) > sizeof(mp_limb_t).
94 When sh < 0, the cast must be performed after the shift
95 for the case sizeof(intmax_t) == sizeof(mp_limb_t), as
96 mp_limb_t is unsigned, therefore not representable as an
97 intmax_t when the MSB is 1 (this is the case here). */
98 MPFR_ASSERTD (sh < GMP_NUMB_BITS && -sh < GMP_NUMB_BITS);
99 r += (sh >= 0
100 ? (intmax_t) xp[n] << sh
101 : (intmax_t) (xp[n] >> (-sh)));
102 }
103 }
104 else
105 {
106 /* See the comments for the case x positive. */
107 for (n = MPFR_LIMB_SIZE (x) - 1; n >= 0 && sh >= 0; n--)
108 {
109 sh -= GMP_NUMB_BITS;
110 MPFR_ASSERTD (sh < GMP_NUMB_BITS && -sh < GMP_NUMB_BITS);
111 r -= (sh >= 0
112 ? (intmax_t) xp[n] << sh
113 : (intmax_t) (xp[n] >> (-sh)));
114 }
115 }
116 }
117
118 mpfr_clear (x);
119
120 return r;
121 }
122
123 #endif
124