xref: /dflybsd-src/contrib/mpfr/src/fits_s.h (revision 2786097444a0124b5d33763854de247e230c6629)

/* mpfr_fits_*_p -- test whether an mpfr fits a C signed type.

Copyright 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
Contributed by the AriC and Caramel projects, INRIA.

This file is part of the GNU MPFR Library.

The GNU MPFR Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 3 of the License, or (at your
option) any later version.

The GNU MPFR Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
License for more details.

You should have received a copy of the GNU Lesser General Public License
along with the GNU MPFR Library; see the file COPYING.LESSER.  If not, see
http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */

#include "mpfr-impl.h"

/* The original version of this file came from GMP's mpf/fits_s.h;
   it has been adapted for MPFR.  In particular, the result can be
   rounded away from zero. */

int
FUNCTION (mpfr_srcptr f, mpfr_rnd_t rnd)
{
  mpfr_exp_t e;
  int prec;
  mpfr_t x;
  int neg;
  int res;

  if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (f)))
    /* Zero always fit */
    return MPFR_IS_ZERO (f) ? 1 : 0;

  /* now it fits if either
     (a) MINIMUM <= f <= MAXIMUM
     (b) or MINIMUM <= round(f, prec(slong), rnd) <= MAXIMUM */

  e = MPFR_GET_EXP (f);
  if (e < 1)
    return 1; /* |f| < 1: always fits */

  neg = MPFR_IS_NEG (f);

  /* let EXTREMUM be MAXIMUM if f > 0, and MINIMUM if f < 0 */

  /* first compute prec(EXTREMUM), this could be done at configure time,
     but the result can depend on neg (the loop is moved inside the "if"
     to give the compiler a better chance to compute prec statically) */
  if (neg)
    {
      unsigned TYPE s;
      /* In C89, the division on negative integers isn't well-defined. */
      s = SAFE_ABS (unsigned TYPE, MINIMUM);
      for (prec = 0; s != 0; s /= 2, prec ++);
    }
  else
    {
      TYPE s;
      s = MAXIMUM;
      for (prec = 0; s != 0; s /= 2, prec ++);
    }

  /* EXTREMUM needs prec bits, i.e. 2^(prec-1) <= |EXTREMUM| < 2^prec */

   /* if e <= prec - 1, then f < 2^(prec-1) <= |EXTREMUM| */
  if (e <= prec - 1)
    return 1;

  /* if e >= prec + 1, then f >= 2^prec > |EXTREMUM| */
  if (e >= prec + 1)
    return 0;

  MPFR_ASSERTD (e == prec);

  /* hard case: first round to prec bits, then check */
  mpfr_init2 (x, prec);
  mpfr_set (x, f, rnd);
  res = neg ? (mpfr_cmp_si (x, MINIMUM) >= 0) : (MPFR_GET_EXP (x) == e);
  mpfr_clear (x);
  return res;
}