mul_1.c

a very popular packet of cryptography tools,it encloses the most common used algorithm and protocols

/* mpn_mul_1 -- Multiply a limb vector with a single limb and store the
   product in a second limb vector.

Copyright 1991, 1992, 1993, 1994, 1996, 2000, 2001, 2002 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., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */

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


#if GMP_NAIL_BITS == 0

mp_limb_t
mpn_mul_1 (mp_ptr rp, mp_srcptr up, mp_size_t n, mp_limb_t vl)
{
  mp_limb_t ul, cl, hpl, lpl;

  ASSERT (n >= 1);
  ASSERT (MPN_SAME_OR_INCR_P (rp, up, n));

  cl = 0;
  do
    {
      ul = *up++;
      umul_ppmm (hpl, lpl, ul, vl);

      lpl += cl;
      cl = (lpl < cl) + hpl;

      *rp++ = lpl;
    }
  while (--n != 0);

  return cl;
}

#endif

#if GMP_NAIL_BITS >= 1

mp_limb_t
mpn_mul_1 (mp_ptr rp, mp_srcptr up, mp_size_t n, mp_limb_t vl)
{
  mp_limb_t shifted_vl, ul, lpl, hpl, prev_hpl, xw, cl, xl;

  ASSERT (n >= 1);
  ASSERT (MPN_SAME_OR_INCR_P (rp, up, n));
  ASSERT_MPN (up, n);
  ASSERT_LIMB (vl);

  shifted_vl = vl << GMP_NAIL_BITS;
  cl = 0;
  prev_hpl = 0;
  do
    {
      ul = *up++;

      umul_ppmm (hpl, lpl, ul, shifted_vl);
      lpl >>= GMP_NAIL_BITS;
      xw = prev_hpl + lpl + cl;
      cl = xw >> GMP_NUMB_BITS;
      xl = xw & GMP_NUMB_MASK;
      *rp++ = xl;
      prev_hpl = hpl;
    }
  while (--n != 0);

  return prev_hpl + cl;
}

#endif