1/* mpn_add_n -- Add two limb vectors of equal, non-zero length.
2
3Copyright (C) 1992-2022 Free Software Foundation, Inc.
4
5This file is part of the GNU MP Library.
6
7The GNU MP Library is free software; you can redistribute it and/or modify
8it under the terms of the GNU Lesser General Public License as published by
9the Free Software Foundation; either version 2.1 of the License, or (at your
10option) any later version.
11
12The GNU MP Library is distributed in the hope that it will be useful, but
13WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
14or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
15License for more details.
16
17You should have received a copy of the GNU Lesser General Public License
18along with the GNU MP Library; see the file COPYING.LIB. If not, see
19<https://www.gnu.org/licenses/>. */
20
21#include <gmp.h>
22#include "gmp-impl.h"
23
24mp_limb_t
25mpn_add_n (mp_ptr res_ptr, mp_srcptr s1_ptr, mp_srcptr s2_ptr, mp_size_t size)
26{
27 register mp_limb_t x, y, cy;
28 register mp_size_t j;
29
30 /* The loop counter and index J goes from -SIZE to -1. This way
31 the loop becomes faster. */
32 j = -size;
33
34 /* Offset the base pointers to compensate for the negative indices. */
35 s1_ptr -= j;
36 s2_ptr -= j;
37 res_ptr -= j;
38
39 cy = 0;
40 do
41 {
42 y = s2_ptr[j];
43 x = s1_ptr[j];
44 y += cy; /* add previous carry to one addend */
45 cy = (y < cy); /* get out carry from that addition */
46 y = x + y; /* add other addend */
47 cy = (y < x) + cy; /* get out carry from that add, combine */
48 res_ptr[j] = y;
49 }
50 while (++j != 0);
51
52 return cy;
53}
54

source code of glibc/stdlib/add_n.c