1/* mpfr_frexp -- convert to integral and fractional parts
2
3Copyright 2011-2023 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
25int
26mpfr_frexp (mpfr_exp_t *exp, mpfr_ptr y, mpfr_srcptr x, mpfr_rnd_t rnd)
27{
28  int inex;
29  mpfr_flags_t saved_flags = __gmpfr_flags;
30  MPFR_BLOCK_DECL (flags);
31
32  MPFR_LOG_FUNC
33    (("x[%Pd]=%.*Rg rnd=%d", mpfr_get_prec (x), mpfr_log_prec, x, rnd),
34     ("y[%Pd]=%.*Rg exp=%" MPFR_EXP_FSPEC "d inex=%d", mpfr_get_prec (y),
35      mpfr_log_prec, y, (mpfr_eexp_t) *exp, inex));
36
37  if (MPFR_UNLIKELY(MPFR_IS_SINGULAR(x)))
38    {
39      if (MPFR_IS_NAN(x))
40        {
41          MPFR_SET_NAN(y);
42          MPFR_RET_NAN; /* exp is unspecified */
43        }
44      else if (MPFR_IS_INF(x))
45        {
46          MPFR_SET_INF(y);
47          MPFR_SET_SAME_SIGN(y,x);
48          MPFR_RET(0); /* exp is unspecified */
49        }
50      else
51        {
52          MPFR_SET_ZERO(y);
53          MPFR_SET_SAME_SIGN(y,x);
54          *exp = 0;
55          MPFR_RET(0);
56        }
57    }
58
59  MPFR_BLOCK (flags, inex = mpfr_set (y, x, rnd));
60  __gmpfr_flags = saved_flags;
61
62  /* Possible overflow due to the rounding, no possible underflow. */
63
64  if (MPFR_UNLIKELY (MPFR_OVERFLOW (flags)))
65    {
66      int inex2;
67
68      /* An overflow here means that the exponent of y would be larger than
69         the one of x, thus x would be rounded to the next power of 2, and
70         the returned y should be 1/2 in absolute value, rounded (i.e. with
71         possible underflow or overflow). This also implies that x and y are
72         different objects, so that the exponent of x has not been lost. */
73      MPFR_LOG_MSG (("Internal overflow\n", 0));
74      MPFR_ASSERTD (x != y);
75      *exp = MPFR_GET_EXP (x) + 1;
76      inex2 = mpfr_set_si_2exp (y, MPFR_INT_SIGN (x), -1, rnd);
77      MPFR_LOG_MSG (("inex=%d inex2=%d\n", inex, inex2));
78      if (inex2 != 0)
79        inex = inex2;
80      MPFR_RET (inex);
81    }
82
83  *exp = MPFR_GET_EXP (y);
84  /* Do not use MPFR_SET_EXP because the range has not been checked yet. */
85  MPFR_EXP (y) = 0;
86  return mpfr_check_range (y, inex, rnd);
87}
88