1/* mpn_add_n -- Add two limb vectors of equal, non-zero length.
2
3Copyright (C) 1992, 1993, 1994, 1996 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 Library General Public License as published by
9the Free Software Foundation; either version 2 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 Library General Public
15License for more details.
16
17You should have received a copy of the GNU Library General Public License
18along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
19the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
20MA 02111-1307, USA. */
21
22#include "gmp.h"
23#include "gmp-impl.h"
24
25mp_limb_t
26#if __STDC__
27mpn_add_n (mp_ptr res_ptr, mp_srcptr s1_ptr, mp_srcptr s2_ptr, mp_size_t size)
28#else
29mpn_add_n (res_ptr, s1_ptr, s2_ptr, size)
30     register mp_ptr res_ptr;
31     register mp_srcptr s1_ptr;
32     register mp_srcptr s2_ptr;
33     mp_size_t size;
34#endif
35{
36  register mp_limb_t x, y, cy;
37  register mp_size_t j;
38
39  /* The loop counter and index J goes from -SIZE to -1.  This way
40     the loop becomes faster.  */
41  j = -size;
42
43  /* Offset the base pointers to compensate for the negative indices.  */
44  s1_ptr -= j;
45  s2_ptr -= j;
46  res_ptr -= j;
47
48  cy = 0;
49  do
50    {
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 + y;		/* add other addend */
56      cy = (y < x) + cy;	/* get out carry from that add, combine */
57      res_ptr[j] = y;
58    }
59  while (++j != 0);
60
61  return cy;
62}
63