mpir/mpn/generic/preinv_mod_1.c

/* mpn_preinv_mod_1 (up, un, d, dinv) -- Divide (UP,,UN) by the normalized D.
   DINV should be 2^(2*GMP_LIMB_BITS) / D - 2^GMP_LIMB_BITS.
   Return the single-limb remainder.

Copyright 1991, 1993, 1994, 2000, 2001, 2002, 2004, 2005 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 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 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 Lesser General Public License
for more details.

You should have received a copy of the GNU Lesser General Public License along
with the GNU MP Library; see the file COPYING.LIB.  If not, write to the Free
Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
USA. */

#include "mpir.h"
#include "gmp-impl.h"
#include "longlong.h"


/* This function used to be documented, but is now considered obsolete.  It
   continues to exist for binary compatibility, even when not required
   internally.  */

mp_limb_t
mpn_preinv_mod_1 (mp_srcptr up, mp_size_t un, mp_limb_t d, mp_limb_t dinv)
{
  mp_size_t i;
  mp_limb_t n0, r;
  mp_limb_t dummy;

  ASSERT (un >= 1);
  ASSERT (d & GMP_LIMB_HIGHBIT);

  r = up[un - 1];
  if (r >= d)
    r -= d;

  for (i = un - 2; i >= 0; i--)
    {
      n0 = up[i];
      udiv_qrnnd_preinv (dummy, r, r, n0, d, dinv);
    }
  return r;
}