1/* mpfr_fits_*_p -- test whether an mpfr fits a C signed 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
25/* The original version of this file came from GMP's mpf/fits_s.h;
26   it has been adapted for MPFR.  In particular, the result can be
27   rounded away from zero. */
28
29int
30FUNCTION (mpfr_srcptr f, mpfr_rnd_t rnd)
31{
32  mpfr_exp_t e;
33  int prec;
34  mpfr_t x;
35  int neg;
36  int res;
37
38  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (f)))
39    /* Zero always fit */
40    return MPFR_IS_ZERO (f) ? 1 : 0;
41
42  /* now it fits if either
43     (a) MINIMUM <= f <= MAXIMUM
44     (b) or MINIMUM <= round(f, prec(slong), rnd) <= MAXIMUM */
45
46  e = MPFR_GET_EXP (f);
47  if (e < 1)
48    return 1; /* |f| < 1: always fits */
49
50  neg = MPFR_IS_NEG (f);
51
52  /* let EXTREMUM be MAXIMUM if f > 0, and MINIMUM if f < 0 */
53
54  /* first compute prec(EXTREMUM), this could be done at configure time,
55     but the result can depend on neg (the loop is moved inside the "if"
56     to give the compiler a better chance to compute prec statically) */
57  if (neg)
58    {
59      unsigned TYPE s;
60      /* In C89, the division on negative integers isn't well-defined. */
61      s = SAFE_ABS (unsigned TYPE, MINIMUM);
62      for (prec = 0; s != 0; s /= 2, prec ++);
63    }
64  else
65    {
66      TYPE s;
67      s = MAXIMUM;
68      for (prec = 0; s != 0; s /= 2, prec ++);
69    }
70
71  /* EXTREMUM needs prec bits, i.e. 2^(prec-1) <= |EXTREMUM| < 2^prec */
72
73   /* if e <= prec - 1, then f < 2^(prec-1) <= |EXTREMUM| */
74  if (e <= prec - 1)
75    return 1;
76
77  /* if e >= prec + 1, then f >= 2^prec > |EXTREMUM| */
78  if (e >= prec + 1)
79    return 0;
80
81  MPFR_ASSERTD (e == prec);
82
83  /* hard case: first round to prec bits, then check */
84  mpfr_init2 (x, prec);
85  mpfr_set (x, f, rnd);
86  res = neg ? (mpfr_cmp_si (x, MINIMUM) >= 0) : (MPFR_GET_EXP (x) == e);
87  mpfr_clear (x);
88  return res;
89}
90