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/* Copyright (C) 1995,1996,1997,1998,1999,2002,2003

        Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C 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 GNU C 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 C Library; if not, write to the Free

   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA

   02111-1307 USA.  */

#include <float.h>

#include <math.h>

#include <stdlib.h>

#include "gmp-impl.h"

/* Convert a `__float128' in IEEE854 quad-precision format to a

   multi-precision integer representing the significand scaled up by its

   number of bits (113 for long double) and an integral power of two

   (MPN frexpl). */

mp_size_t

mpn_extract_flt128 (mp_ptr res_ptr, mp_size_t size,

                      int *expt, int *is_neg,

                      __float128 value)

{

  ieee854_float128 u;

  u.value = value;

  *is_neg = u.ieee.negative;

  *expt = (int) u.ieee.exponent - IEEE854_FLOAT128_BIAS;

#if BITS_PER_MP_LIMB == 32

  res_ptr[0] = u.ieee.mant_low; /* Low-order 32 bits of fraction.  */

  res_ptr[1] = (u.ieee.mant_low >> 32);

  res_ptr[2] = u.ieee.mant_high;

  res_ptr[3] = (u.ieee.mant_high >> 32); /* High-order 32 bits.  */

  #define N 4

#elif BITS_PER_MP_LIMB == 64

  res_ptr[0] = u.ieee.mant_low;

  res_ptr[1] = u.ieee.mant_high;

  #define N 2

#else

  #error "mp_limb size " BITS_PER_MP_LIMB "not accounted for"

#endif

/* The format does not fill the last limb.  There are some zeros.  */

#define NUM_LEADING_ZEROS (BITS_PER_MP_LIMB \

                           - (FLT128_MANT_DIG - ((N - 1) * BITS_PER_MP_LIMB)))

  if (u.ieee.exponent == 0)

    {

      /* A biased exponent of zero is a special case.

         Either it is a zero or it is a denormal number.  */

      if (res_ptr[0] == 0 && res_ptr[1] == 0

          && res_ptr[N - 2] == 0 && res_ptr[N - 1] == 0) /* Assumes N<=4.  */

        /* It's zero.  */

        *expt = 0;

      else

        {

          /* It is a denormal number, meaning it has no implicit leading

             one bit, and its exponent is in fact the format minimum.  */

          int cnt;

#if N == 2

          if (res_ptr[N - 1] != 0)

            {

              count_leading_zeros (cnt, res_ptr[N - 1]);

              cnt -= NUM_LEADING_ZEROS;

              res_ptr[N - 1] = res_ptr[N - 1] << cnt

                               | (res_ptr[0] >> (BITS_PER_MP_LIMB - cnt));

              res_ptr[0] <<= cnt;

              *expt = FLT128_MIN_EXP - 1 - cnt;

            }

          else

            {

              count_leading_zeros (cnt, res_ptr[0]);

              if (cnt >= NUM_LEADING_ZEROS)

                {

                  res_ptr[N - 1] = res_ptr[0] << (cnt - NUM_LEADING_ZEROS);

                  res_ptr[0] = 0;

                }

              else

                {

                  res_ptr[N - 1] = res_ptr[0] >> (NUM_LEADING_ZEROS - cnt);

                  res_ptr[0] <<= BITS_PER_MP_LIMB - (NUM_LEADING_ZEROS - cnt);

                }

              *expt = FLT128_MIN_EXP - 1

                - (BITS_PER_MP_LIMB - NUM_LEADING_ZEROS) - cnt;

            }

#else

          int j, k, l;

          for (j = N - 1; j > 0; j--)

            if (res_ptr[j] != 0)

              break;

          count_leading_zeros (cnt, res_ptr[j]);

          cnt -= NUM_LEADING_ZEROS;

          l = N - 1 - j;

          if (cnt < 0)

            {

              cnt += BITS_PER_MP_LIMB;

              l--;

            }

          if (!cnt)

            for (k = N - 1; k >= l; k--)

              res_ptr[k] = res_ptr[k-l];

          else

            {

              for (k = N - 1; k > l; k--)

                res_ptr[k] = res_ptr[k-l] << cnt

                             | res_ptr[k-l-1] >> (BITS_PER_MP_LIMB - cnt);

              res_ptr[k--] = res_ptr[0] << cnt;

            }

          for (; k >= 0; k--)

            res_ptr[k] = 0;

          *expt = FLT128_MIN_EXP - 1 - l * BITS_PER_MP_LIMB - cnt;

#endif

        }

    }

  else

    /* Add the implicit leading one bit for a normalized number.  */

    res_ptr[N - 1] |= (mp_limb_t) 1 << (FLT128_MANT_DIG - 1

                                        - ((N - 1) * BITS_PER_MP_LIMB));

  return N;

}