/* Helper function for high degree Toom-Cook algorithms.

   Contributed to the GNU project by Marco Bodrato.

   THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE.  IT IS ONLY

   SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES.  IN FACT, IT IS ALMOST

   GUARANTEED THAT IT WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE.

Copyright 2009, 2010 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-impl.h"

/* Gets {pp,n} and (sign?-1:1)*{np,n}. Computes at once:

     {pp,n} <- ({pp,n}+{np,n})/2^{ps+1}

     {pn,n} <- ({pp,n}-{np,n})/2^{ns+1}

   Finally recompose them obtaining:

     {pp,n+off} <- {pp,n}+{np,n}*2^{off*GMP_NUMB_BITS}

*/

void

mpn_toom_couple_handling (mp_ptr pp, mp_size_t n, mp_ptr np,

        unsigned nsign, mp_size_t off, int ps, int ns)

{

  if (nsign) {

#ifdef HAVE_NATIVE_mpn_rsh1sub_n

    mpn_rsh1sub_n (np, pp, np, n);

#else

    mpn_sub_n (np, pp, np, n);

    mpn_rshift (np, np, n, 1);

#endif

  } else {

#ifdef HAVE_NATIVE_mpn_rsh1add_n

    mpn_rsh1add_n (np, pp, np, n);

#else

    mpn_add_n (np, pp, np, n);

    mpn_rshift (np, np, n, 1);

#endif

  }

#ifdef HAVE_NATIVE_mpn_rsh1sub_n

  if (ps == 1)

    mpn_rsh1sub_n (pp, pp, np, n);

  else

#endif

  {

    mpn_sub_n (pp, pp, np, n);

    if (ps > 0)

      mpn_rshift (pp, pp, n, ps);

  }

  if (ns > 0)

    mpn_rshift (np, np, n, ns);

  pp[n] = mpn_add_n (pp+off, pp+off, np, n-off);

  ASSERT_NOCARRY (mpn_add_1(pp+n, np+n-off, off, pp[n]) );

}