1/* mpfr_get_z -- get a multiple-precision integer from
2                 a floating-point number
3
4Copyright 2004, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
5Contributed by the AriC and Caramel projects, INRIA.
6
7This file is part of the GNU MPFR Library.
8
9The GNU MPFR Library is free software; you can redistribute it and/or modify
10it under the terms of the GNU Lesser General Public License as published by
11the Free Software Foundation; either version 3 of the License, or (at your
12option) any later version.
13
14The GNU MPFR Library is distributed in the hope that it will be useful, but
15WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
16or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
17License for more details.
18
19You should have received a copy of the GNU Lesser General Public License
20along with the GNU MPFR Library; see the file COPYING.LESSER.  If not, see
21http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
2251 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
23
24#include "mpfr-impl.h"
25
26int
27mpfr_get_z (mpz_ptr z, mpfr_srcptr f, mpfr_rnd_t rnd)
28{
29  int inex;
30  mpfr_t r;
31  mpfr_exp_t exp;
32
33  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (f)))
34    {
35      if (MPFR_UNLIKELY (MPFR_NOTZERO (f)))
36        MPFR_SET_ERANGE ();
37      mpz_set_ui (z, 0);
38      /* The ternary value is 0 even for infinity. Giving the rounding
39         direction in this case would not make much sense anyway, and
40         the direction would not necessarily match rnd. */
41      return 0;
42    }
43
44  exp = MPFR_GET_EXP (f);
45  /* if exp <= 0, then |f|<1, thus |o(f)|<=1 */
46  MPFR_ASSERTN (exp < 0 || exp <= MPFR_PREC_MAX);
47  mpfr_init2 (r, (exp < (mpfr_exp_t) MPFR_PREC_MIN ?
48                  MPFR_PREC_MIN : (mpfr_prec_t) exp));
49  inex = mpfr_rint (r, f, rnd);
50  MPFR_ASSERTN (inex != 1 && inex != -1); /* integral part of f is
51                                             representable in r */
52  MPFR_ASSERTN (MPFR_IS_FP (r));
53  exp = mpfr_get_z_2exp (z, r);
54  if (exp >= 0)
55    mpz_mul_2exp (z, z, exp);
56  else
57    mpz_fdiv_q_2exp (z, z, -exp);
58  mpfr_clear (r);
59
60  return inex;
61}
62