1/* mpihelp-mul_1.c  -  MPI helper functions
2 * Copyright (C) 1994, 1996, 1997, 1998, 2001,
3 *               2002 Free Software Foundation, Inc.
4 *
5 * This file is part of Libgcrypt.
6 *
7 * Libgcrypt is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU Lesser General Public License as
9 * published by the Free Software Foundation; either version 2.1 of
10 * the License, or (at your option) any later version.
11 *
12 * Libgcrypt is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with this program; if not, write to the Free Software
19 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
20 *
21 * Note: This code is heavily based on the GNU MP Library.
22 *	 Actually it's the same code with only minor changes in the
23 *	 way the data is stored; this is to support the abstraction
24 *	 of an optional secure memory allocation which may be used
25 *	 to avoid revealing of sensitive data due to paging etc.
26 */
27
28#include <config.h>
29#include <stdio.h>
30#include <stdlib.h>
31#include "mpi-internal.h"
32#include "longlong.h"
33
34mpi_limb_t
35_gcry_mpih_mul_1( mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
36						    mpi_limb_t s2_limb)
37{
38  mpi_limb_t cy_limb;
39  mpi_size_t j;
40  mpi_limb_t prod_high, prod_low;
41
42  /* The loop counter and index J goes from -S1_SIZE to -1.  This way
43   * the loop becomes faster.  */
44  j = -s1_size;
45
46  /* Offset the base pointers to compensate for the negative indices.  */
47  s1_ptr -= j;
48  res_ptr -= j;
49
50  cy_limb = 0;
51  do
52    {
53      umul_ppmm( prod_high, prod_low, s1_ptr[j], s2_limb );
54      prod_low += cy_limb;
55      cy_limb = (prod_low < cy_limb?1:0) + prod_high;
56      res_ptr[j] = prod_low;
57    }
58  while( ++j );
59
60  return cy_limb;
61}
62
63