1/* mpihelp-mul_1.c  -  MPI helper functions
 2 * Copyright (C) 1994, 1996, 1997, 1998, 2001 Free Software Foundation, Inc.
 3 *
 4 * This file is part of GnuPG.
 5 *
 6 * GnuPG is free software; you can redistribute it and/or modify
 7 * it under the terms of the GNU General Public License as published by
 8 * the Free Software Foundation; either version 2 of the License, or
 9 * (at your option) any later version.
10 *
11 * GnuPG is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
19 *
20 * Note: This code is heavily based on the GNU MP Library.
21 *	 Actually it's the same code with only minor changes in the
22 *	 way the data is stored; this is to support the abstraction
23 *	 of an optional secure memory allocation which may be used
24 *	 to avoid revealing of sensitive data due to paging etc.
25 *	 The GNU MP Library itself is published under the LGPL;
26 *	 however I decided to publish this code under the plain GPL.
27 */
28
29#include "mpi-internal.h"
30#include "longlong.h"
31
32mpi_limb_t
33mpihelp_mul_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
34	      mpi_limb_t s2_limb)
35{
36	mpi_limb_t cy_limb;
37	mpi_size_t j;
38	mpi_limb_t prod_high, prod_low;
39
40	/* The loop counter and index J goes from -S1_SIZE to -1.  This way
41	 * the loop becomes faster.  */
42	j = -s1_size;
43
44	/* Offset the base pointers to compensate for the negative indices.  */
45	s1_ptr -= j;
46	res_ptr -= j;
47
48	cy_limb = 0;
49	do {
50		umul_ppmm(prod_high, prod_low, s1_ptr[j], s2_limb);
51		prod_low += cy_limb;
52		cy_limb = (prod_low < cy_limb ? 1 : 0) + prod_high;
53		res_ptr[j] = prod_low;
54	} while (++j);
55
56	return cy_limb;
57}