/* 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.mantissa3; /* Low-order 32 bits of fraction.  */
 res_ptr[1] = u.ieee.mantissa2;
 res_ptr[2] = u.ieee.mantissa1;
 res_ptr[3] = u.ieee.mantissa0; /* High-order 32 bits.  */
 #define N 4
#elif BITS_PER_MP_LIMB == 64
 res_ptr[0] = ((mp_limb_t) u.ieee.mantissa2 << 32) | u.ieee.mantissa3;
 res_ptr[1] = ((mp_limb_t) u.ieee.mantissa0 << 32) | u.ieee.mantissa1;
 #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;
}