/* mpz_com(mpz_ptr dst, mpz_ptr src) -- Assign the bit-complemented value of

   SRC to DST.

Copyright 1991, 1993, 1994, 1996, 2001, 2003, 2012 Free Software Foundation,

Inc.

This file is part of the GNU MP Library.

The GNU MP Library is free software; you can redistribute it and/or modify

it under the terms of either:

  * the GNU Lesser General Public License as published by the Free

    Software Foundation; either version 3 of the License, or (at your

    option) any later version.

or

  * the GNU General Public License as published by the Free Software

    Foundation; either version 2 of the License, or (at your option) any

    later version.

or both in parallel, as here.

The GNU MP 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 General Public License

for more details.

You should have received copies of the GNU General Public License and the

GNU Lesser General Public License along with the GNU MP Library.  If not,

see https://www.gnu.org/licenses/.  */

#include "gmp.h"

#include "gmp-impl.h"

void

mpz_com (mpz_ptr dst, mpz_srcptr src)

{

  mp_size_t size = SIZ (src);

  mp_srcptr src_ptr;

  mp_ptr dst_ptr;

  if (size >= 0)

    {

      /* As with infinite precision: one's complement, two's complement.

	 But this can be simplified using the identity -x = ~x + 1.

	 So we're going to compute (~~x) + 1 = x + 1!  */

      if (UNLIKELY (size == 0))

	{

	  /* special case, as mpn_add_1 wants size!=0 */

	  PTR (dst)[0] = 1;

	  SIZ (dst) = -1;

	}

      else

	{

	  mp_limb_t cy;

	  dst_ptr = MPZ_REALLOC (dst, size + 1);

	  src_ptr = PTR (src);

	  cy = mpn_add_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);

	  dst_ptr[size] = cy;

	  size += cy;

	  /* Store a negative size, to indicate ones-extension.  */

	  SIZ (dst) = -size;

      }

    }

  else

    {

      /* As with infinite precision: two's complement, then one's complement.

	 But that can be simplified using the identity -x = ~(x - 1).

	 So we're going to compute ~~(x - 1) = x - 1!  */

      size = -size;

      dst_ptr = MPZ_REALLOC (dst, size);

      src_ptr = PTR (src);

      mpn_sub_1 (dst_ptr, src_ptr, size, (mp_limb_t) 1);

      size -= dst_ptr[size - 1] == 0;

      /* Store a positive size, to indicate zero-extension.  */

      SIZ (dst) = size;

    }

}