1/* mpfr_get_si -- convert a floating-point number to a signed long.
2
3Copyright 2003, 2004, 2005, 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
25long
26mpfr_get_si (mpfr_srcptr f, mpfr_rnd_t rnd)
27{
28  mpfr_prec_t prec;
29  long s;
30  mpfr_t x;
31
32  if (MPFR_UNLIKELY (!mpfr_fits_slong_p (f, rnd)))
33    {
34      MPFR_SET_ERANGE ();
35      return MPFR_IS_NAN (f) ? 0 :
36        MPFR_IS_NEG (f) ? LONG_MIN : LONG_MAX;
37    }
38
39  if (MPFR_IS_ZERO (f))
40    return (long) 0;
41
42  /* determine prec of long */
43  for (s = LONG_MIN, prec = 0; s != 0; s /= 2, prec++)
44    { }
45
46  /* first round to prec bits */
47  mpfr_init2 (x, prec);
48  mpfr_rint (x, f, rnd);
49
50  /* warning: if x=0, taking its exponent is illegal */
51  if (MPFR_UNLIKELY (MPFR_IS_ZERO(x)))
52    s = 0;
53  else
54    {
55      mp_limb_t a;
56      mp_size_t n;
57      mpfr_exp_t exp;
58
59      /* now the result is in the most significant limb of x */
60      exp = MPFR_GET_EXP (x); /* since |x| >= 1, exp >= 1 */
61      n = MPFR_LIMB_SIZE(x);
62      a = MPFR_MANT(x)[n - 1] >> (GMP_NUMB_BITS - exp);
63      s = MPFR_SIGN(f) > 0 ? a : a <= LONG_MAX ? - (long) a : LONG_MIN;
64    }
65
66  mpfr_clear (x);
67
68  return s;
69}
70