/* mpfr_get_sj -- convert a MPFR number to a huge machine signed integer

Copyright 2004, 2006, 2007 Free Software Foundation, Inc.

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 St, 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

intmax_t
mpfr_get_sj (mpfr_srcptr f, mpfr_rnd_t rnd)
{
  intmax_t r;
  mp_prec_t prec;
  mpfr_t x;

  if (!mpfr_fits_intmax_p (f, rnd))
    {
      MPFR_SET_ERANGE ();
      return MPFR_IS_NEG (f) ? INTMAX_MIN : INTMAX_MAX;
    }
  if (MPFR_IS_ZERO (f))
     return (intmax_t) 0;

  /* determine the precision of intmax_t */
  for (r = INTMAX_MIN, prec = 0; r != 0; r /= 2, prec++)
    {
    }
  /* Note: though INTMAX_MAX would have been sufficient for the conversion,
     we chose INTMAX_MIN so that INTMAX_MIN - 1 is always representable in
     precision prec; this is useful to detect overflows in GMP_RNDZ (will
     be needed later). */

  /* Now, r = 0. */

  mpfr_init2 (x, prec);
  mpfr_rint (x, f, rnd);
  MPFR_ASSERTN (MPFR_IS_FP (x));

  if (MPFR_NOTZERO (x))
    {
      mp_limb_t *xp;
      int sh, n;        /* An int should be sufficient in this context. */

      xp = MPFR_MANT (x);
      sh = MPFR_GET_EXP (x);
      MPFR_ASSERTN ((mp_prec_t) sh <= prec);
      if (INTMAX_MIN + INTMAX_MAX != 0
          && MPFR_UNLIKELY ((mp_prec_t) sh == prec))
        {
          /* 2's complement and x <= INTMAX_MIN: in the case mp_limb_t
             has the same size as intmax_t, we cannot use the code in
             the for loop since the operations would be performed in
             unsigned arithmetic. */
          MPFR_ASSERTN (MPFR_IS_NEG (x) && (mpfr_powerof2_raw (x)));
          r = INTMAX_MIN;
        }
      else if (MPFR_IS_POS (x))
        {
          for (n = MPFR_LIMB_SIZE (x) - 1; n >= 0; n--)
            {
              sh -= BITS_PER_MP_LIMB;
              /* Note the concerning the casts below:
                 When sh >= 0, the cast must be performed before the shift
                 for the case sizeof(intmax_t) > sizeof(mp_limb_t).
                 When sh < 0, the cast must be performed after the shift
                 for the case sizeof(intmax_t) == sizeof(mp_limb_t), as
                 mp_limb_t is unsigned, therefore not representable as an
                 intmax_t when the MSB is 1 (this is the case here). */
              r += (sh >= 0
                    ? (intmax_t) xp[n] << sh
                    : (intmax_t) (xp[n] >> (-sh)));
            }
        }
      else
        {
          for (n = MPFR_LIMB_SIZE (x) - 1; n >= 0; n--)
            {
              sh -= BITS_PER_MP_LIMB;
              /* See above for the note concerning the casts. */
              r -= (sh >= 0
                    ? (intmax_t) xp[n] << sh
                    : (intmax_t) (xp[n] >> (-sh)));
            }
        }
    }

  mpfr_clear (x);

  return r;
}

#endif