1/* mpihelp-add_1.c  -  MPI helper functions
 2 * Copyright (C) 1994, 1996, 1997, 1998,
 3 *               2000 Free Software Foundation, Inc.
 4 *
 5 * This file is part of GnuPG.
 6 *
 7 * GnuPG is free software; you can redistribute it and/or modify
 8 * it under the terms of the GNU General Public License as published by
 9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 *
12 * GnuPG 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 General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * 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 *	 The GNU MP Library itself is published under the LGPL;
27 *	 however I decided to publish this code under the plain GPL.
28 */
29
30#include "mpi-internal.h"
31#include "longlong.h"
32
33mpi_limb_t
34mpihelp_add_n(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
35	      mpi_ptr_t s2_ptr, mpi_size_t size)
36{
37	mpi_limb_t x, y, cy;
38	mpi_size_t j;
39
40	/* The loop counter and index J goes from -SIZE to -1.  This way
41	   the loop becomes faster.  */
42	j = -size;
43
44	/* Offset the base pointers to compensate for the negative indices. */
45	s1_ptr -= j;
46	s2_ptr -= j;
47	res_ptr -= j;
48
49	cy = 0;
50	do {
51		y = s2_ptr[j];
52		x = s1_ptr[j];
53		y += cy;	/* add previous carry to one addend */
54		cy = y < cy;	/* get out carry from that addition */
55		y += x;		/* add other addend */
56		cy += y < x;	/* get out carry from that add, combine */
57		res_ptr[j] = y;
58	} while (++j);
59
60	return cy;
61}

 1// SPDX-License-Identifier: GPL-2.0-or-later
 2/* mpihelp-add_1.c  -  MPI helper functions
 3 * Copyright (C) 1994, 1996, 1997, 1998,
 4 *               2000 Free Software Foundation, Inc.
 5 *
 6 * This file is part of GnuPG.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 7 *
 8 * Note: This code is heavily based on the GNU MP Library.
 9 *	 Actually it's the same code with only minor changes in the
10 *	 way the data is stored; this is to support the abstraction
11 *	 of an optional secure memory allocation which may be used
12 *	 to avoid revealing of sensitive data due to paging etc.
13 *	 The GNU MP Library itself is published under the LGPL;
14 *	 however I decided to publish this code under the plain GPL.
15 */
16
17#include "mpi-internal.h"
18#include "longlong.h"
19
20mpi_limb_t
21mpihelp_add_n(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
22	      mpi_ptr_t s2_ptr, mpi_size_t size)
23{
24	mpi_limb_t x, y, cy;
25	mpi_size_t j;
26
27	/* The loop counter and index J goes from -SIZE to -1.  This way
28	   the loop becomes faster.  */
29	j = -size;
30
31	/* Offset the base pointers to compensate for the negative indices. */
32	s1_ptr -= j;
33	s2_ptr -= j;
34	res_ptr -= j;
35
36	cy = 0;
37	do {
38		y = s2_ptr[j];
39		x = s1_ptr[j];
40		y += cy;	/* add previous carry to one addend */
41		cy = y < cy;	/* get out carry from that addition */
42		y += x;		/* add other addend */
43		cy += y < x;	/* get out carry from that add, combine */
44		res_ptr[j] = y;
45	} while (++j);
46
47	return cy;
48}