/* Copyright (C) 1995-2018 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, see

   <http://www.gnu.org/licenses/>.  */

#include "gmp.h"

#include "gmp-impl.h"

#include "longlong.h"

#include <ieee754.h>

#include <float.h>

#include <math.h>

#include <stdlib.h>

/* Convert a `long double' in IEEE854 standard double-precision format to a

   multi-precision integer representing the significand scaled up by its

   number of bits (64 for long double) and an integral power of two

   (MPN frexpl). */

mp_size_t

__mpn_extract_long_double (mp_ptr res_ptr, mp_size_t size,

			   int *expt, int *is_neg,

			   long double value)

{

  union ieee854_long_double u;

  u.d = value;

  *is_neg = u.ieee.negative;

  *expt = (int) u.ieee.exponent - IEEE854_LONG_DOUBLE_BIAS;

#if BITS_PER_MP_LIMB == 32

  res_ptr[0] = u.ieee.mantissa1; /* Low-order 32 bits of fraction.  */

  res_ptr[1] = u.ieee.mantissa0; /* High-order 32 bits.  */

  #define N 2

#elif BITS_PER_MP_LIMB == 64

  /* Hopefully the compiler will combine the two bitfield extracts

     and this composition into just the original quadword extract.  */

  res_ptr[0] = ((mp_limb_t) u.ieee.mantissa0 << 32) | u.ieee.mantissa1;

  #define N 1

#else

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

#endif

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

	/* 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 (res_ptr[N - 1] != 0)

	    {

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

	      if (cnt != 0)

		{

#if N == 2

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

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

	          res_ptr[0] <<= cnt;

#else

	          res_ptr[N - 1] <<= cnt;

#endif

		}

	      *expt = LDBL_MIN_EXP - 1 - cnt;

	    }

	  else

	    {

	      count_leading_zeros (cnt, res_ptr[0]);

	      res_ptr[N - 1] = res_ptr[0] << cnt;

	      res_ptr[0] = 0;

	      *expt = LDBL_MIN_EXP - 1 - BITS_PER_MP_LIMB - cnt;

	    }

	}

    }

  return N;

}