/* mpfr_fits_intmax_p -- test whether an mpfr fits an intmax_t.

Copyright 2004, 2006 Free Software Foundation, Inc.
Contributed by the Spaces project, INRIA Lorraine.

This file is part of the MPFR Library.

The 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 2.1 of the License, or (at your
option) any later version.

The 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 MPFR Library; see the file COPYING.LIB.  If not, write to
the Free Software Foundation, Inc., 51 Franklin Place, Fifth Floor, Boston,
MA 02110-1301, USA. */

#if HAVE_CONFIG_H
# include "config.h"            /* for a build within gmp */
#endif

/* The ISO C99 standard specifies that in C++ implementations the
   INTMAX_MAX, ... macros should only be defined if explicitly requested.  */
#if defined __cplusplus
# define __STDC_LIMIT_MACROS
# define __STDC_CONSTANT_MACROS
#endif

#ifdef HAVE_STDINT_H
# include <stdint.h>
#endif
#ifdef HAVE_INTTYPES_H
# include <inttypes.h>
#endif

#include "mpfr-impl.h"

#ifdef _MPFR_H_HAVE_INTMAX_T

/* We can't use fits_s.h <= mpfr_cmp_ui */
int
mpfr_fits_intmax_p (mpfr_srcptr f, mp_rnd_t rnd)
{
  mp_exp_t exp;
  mp_prec_t prec;
  intmax_t s;
  mpfr_t x, y;
  int neg;
  int res;

  if (MPFR_IS_NAN (f) || MPFR_IS_INF (f))
    return 0; /* does not fit */

  if (MPFR_IS_ZERO (f))
    return 1; /* zero always fits */

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

  exp = MPFR_EXP (f);
  if (exp < 1)
    return 1; /* |f| < 1: always fits */

  neg = (MPFR_SIGN (f) > 0) ? 0 : 1;

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

  /* first compute prec(EXTREMUM), this could be done at configure time */
  s = (neg) ? INTMAX_MIN : INTMAX_MAX;
  for (prec = 0; s != 0; s /= 2, prec ++);

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

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

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

  /* remains cases exp = prec-1 to prec+1 */

  /* hard case: first round to prec bits, then check */
  mpfr_init2 (x, prec);
  mpfr_init2 (y, prec);

  mpfr_set (x, f, rnd);
  mpfr_set_sj (y, neg ? INTMAX_MIN : INTMAX_MAX, GMP_RNDN);

  res = (neg
         ? (mpfr_cmp (x, y) >= 0)
         : (mpfr_cmp (x, y) <= 0));

  mpfr_clear (y);
  mpfr_clear (x);

  return res;
}

#endif