1/* mpfr_fits_*_p -- test whether an mpfr fits a C unsigned type.
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
25int
26FUNCTION (mpfr_srcptr f, mpfr_rnd_t rnd)
27{
28  mpfr_exp_t e;
29  int prec;
30  TYPE s;
31  mpfr_t x;
32  int res;
33
34  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (f)))
35    /* Zero always fit */
36    return MPFR_IS_ZERO (f) ? 1 : 0;
37  else if (MPFR_IS_NEG (f))
38    /* Negative numbers don't fit */
39    return 0;
40  /* now it fits if
41     (a) f <= MAXIMUM
42     (b) round(f, prec(slong), rnd) <= MAXIMUM */
43
44  e = MPFR_GET_EXP (f);
45
46  /* first compute prec(MAXIMUM); fits in an int */
47  for (s = MAXIMUM, prec = 0; s != 0; s /= 2, prec ++);
48
49  /* MAXIMUM needs prec bits, i.e. MAXIMUM = 2^prec - 1 */
50
51  /* if e <= prec - 1, then f < 2^(prec-1) < MAXIMUM */
52  if (e <= prec - 1)
53    return 1;
54
55  /* if e >= prec + 1, then f >= 2^prec > MAXIMUM */
56  if (e >= prec + 1)
57    return 0;
58
59  MPFR_ASSERTD (e == prec);
60
61  /* hard case: first round to prec bits, then check */
62  mpfr_init2 (x, prec);
63  mpfr_set (x, f, rnd);
64  res = MPFR_GET_EXP (x) == e;
65  mpfr_clear (x);
66  return res;
67}
68