1 /* mpih-mul2.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
34
35 mpi_limb_t
_gcry_mpih_addmul_1(mpi_ptr_t res_ptr,mpi_ptr_t s1_ptr,mpi_size_t s1_size,mpi_limb_t s2_limb)36 _gcry_mpih_addmul_1( mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
37 mpi_size_t s1_size, mpi_limb_t s2_limb)
38 {
39 mpi_limb_t cy_limb;
40 mpi_size_t j;
41 mpi_limb_t prod_high, prod_low;
42 mpi_limb_t x;
43
44 /* The loop counter and index J goes from -SIZE to -1. This way
45 * the loop becomes faster. */
46 j = -s1_size;
47 res_ptr -= j;
48 s1_ptr -= j;
49
50 cy_limb = 0;
51 do
52 {
53 umul_ppmm( prod_high, prod_low, s1_ptr[j], s2_limb );
54
55 prod_low += cy_limb;
56 cy_limb = (prod_low < cy_limb?1:0) + prod_high;
57
58 x = res_ptr[j];
59 prod_low = x + prod_low;
60 cy_limb += prod_low < x?1:0;
61 res_ptr[j] = prod_low;
62 }
63 while ( ++j );
64
65 return cy_limb;
66 }
67
68
69