1/* mpfr_get_ui -- convert a floating-point number to an unsigned long.
2
3Copyright 2003, 2004, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
4Contributed by the AriC and Caramel 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
20http://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
25unsigned long
26mpfr_get_ui (mpfr_srcptr f, mpfr_rnd_t rnd)
27{
28  mpfr_prec_t prec;
29  unsigned long s;
30  mpfr_t x;
31  mp_size_t n;
32  mpfr_exp_t exp;
33
34  if (MPFR_UNLIKELY (!mpfr_fits_ulong_p (f, rnd)))
35    {
36      MPFR_SET_ERANGE ();
37      return MPFR_IS_NAN (f) || MPFR_IS_NEG (f) ?
38        (unsigned long) 0 : ULONG_MAX;
39    }
40
41  if (MPFR_IS_ZERO (f))
42    return (unsigned long) 0;
43
44  for (s = ULONG_MAX, prec = 0; s != 0; s /= 2, prec ++)
45    { }
46
47  /* first round to prec bits */
48  mpfr_init2 (x, prec);
49  mpfr_rint (x, f, rnd);
50
51  /* warning: if x=0, taking its exponent is illegal */
52  if (MPFR_IS_ZERO(x))
53    s = 0;
54  else
55    {
56      /* now the result is in the most significant limb of x */
57      exp = MPFR_GET_EXP (x); /* since |x| >= 1, exp >= 1 */
58      n = MPFR_LIMB_SIZE(x);
59      s = MPFR_MANT(x)[n - 1] >> (GMP_NUMB_BITS - exp);
60    }
61
62  mpfr_clear (x);
63
64  return s;
65}
66