/* mpn_dcpi1_bdiv_q -- divide-and-conquer Hensel division with precomputed

   inverse, returning quotient.

   Contributed to the GNU project by Niels Möller and Torbjorn Granlund.

   THE FUNCTIONS IN THIS FILE ARE INTERNAL WITH MUTABLE INTERFACES.  IT IS ONLY

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

   GUARANTEED THAT THEY WILL CHANGE OR DISAPPEAR IN A FUTURE GMP RELEASE.

Copyright 2006, 2007, 2009-2011, 2017 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"

#if 0       /* unused, so leave out for now */

static mp_size_t

mpn_dcpi1_bdiv_q_n_itch (mp_size_t n)

{

  /* NOTE: Depends on mullo_n and mpn_dcpi1_bdiv_qr_n interface */

  return n;

}

#endif

/* Computes Q = - N / D mod B^n, destroys N.

   N = {np,n}

   D = {dp,n}

*/

static void

mpn_dcpi1_bdiv_q_n (mp_ptr qp,

        mp_ptr np, mp_srcptr dp, mp_size_t n,

        mp_limb_t dinv, mp_ptr tp)

{

  while (ABOVE_THRESHOLD (n, DC_BDIV_Q_THRESHOLD))

    {

      mp_size_t lo, hi;

      mp_limb_t cy;

      lo = n >> 1;      /* floor(n/2) */

      hi = n - lo;      /* ceil(n/2) */

      cy = mpn_dcpi1_bdiv_qr_n (qp, np, dp, lo, dinv, tp);

      mpn_mullo_n (tp, qp, dp + hi, lo);

      mpn_add_n (np + hi, np + hi, tp, lo);

      if (lo < hi)

  {

    cy += mpn_addmul_1 (np + lo, qp, lo, dp[lo]);

    np[n - 1] += cy;

  }

      qp += lo;

      np += lo;

      n -= lo;

    }

  mpn_sbpi1_bdiv_q (qp, np, n, dp, n, dinv);

}

/* Computes Q = - N / D mod B^nn, destroys N.

   N = {np,nn}

   D = {dp,dn}

*/

void

mpn_dcpi1_bdiv_q (mp_ptr qp,

      mp_ptr np, mp_size_t nn,

      mp_srcptr dp, mp_size_t dn,

      mp_limb_t dinv)

{

  mp_size_t qn;

  mp_limb_t cy;

  mp_ptr tp;

  TMP_DECL;

  TMP_MARK;

  ASSERT (dn >= 2);

  ASSERT (nn - dn >= 0);

  ASSERT (dp[0] & 1);

  tp = TMP_SALLOC_LIMBS (dn);

  qn = nn;

  if (qn > dn)

    {

      /* Reduce qn mod dn in a super-efficient manner.  */

      do

  qn -= dn;

      while (qn > dn);

      /* Perform the typically smaller block first.  */

      if (BELOW_THRESHOLD (qn, DC_BDIV_QR_THRESHOLD))

  cy = mpn_sbpi1_bdiv_qr (qp, np, 2 * qn, dp, qn, dinv);

      else

  cy = mpn_dcpi1_bdiv_qr_n (qp, np, dp, qn, dinv, tp);

      if (qn != dn)

  {

    if (qn > dn - qn)

      mpn_mul (tp, qp, qn, dp + qn, dn - qn);

    else

      mpn_mul (tp, dp + qn, dn - qn, qp, qn);

    mpn_incr_u (tp + qn, cy);

    mpn_add (np + qn, np + qn, nn - qn, tp, dn);

    cy = 0;

  }

      np += qn;

      qp += qn;

      qn = nn - qn;

      while (qn > dn)

  {

    mpn_add_1 (np + dn, np + dn, qn - dn, cy);

    cy = mpn_dcpi1_bdiv_qr_n (qp, np, dp, dn, dinv, tp);

    qp += dn;

    np += dn;

    qn -= dn;

  }

      mpn_dcpi1_bdiv_q_n (qp, np, dp, dn, dinv, tp);

    }

  else

    {

      if (BELOW_THRESHOLD (qn, DC_BDIV_Q_THRESHOLD))

  mpn_sbpi1_bdiv_q (qp, np, qn, dp, qn, dinv);

      else

  mpn_dcpi1_bdiv_q_n (qp, np, dp, qn, dinv, tp);

    }

  TMP_FREE;

}