1 /*	$NetBSD: bn_mp_add.c,v 1.1.1.1 2011/04/13 18:14:54 elric Exp $	*/
2 
3 #include <tommath.h>
4 #ifdef BN_MP_ADD_C
5 /* LibTomMath, multiple-precision integer library -- Tom St Denis
6  *
7  * LibTomMath is a library that provides multiple-precision
8  * integer arithmetic as well as number theoretic functionality.
9  *
10  * The library was designed directly after the MPI library by
11  * Michael Fromberger but has been written from scratch with
12  * additional optimizations in place.
13  *
14  * The library is free for all purposes without any express
15  * guarantee it works.
16  *
17  * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
18  */
19 
20 /* high level addition (handles signs) */
21 int mp_add (mp_int * a, mp_int * b, mp_int * c)
22 {
23   int     sa, sb, res;
24 
25   /* get sign of both inputs */
26   sa = a->sign;
27   sb = b->sign;
28 
29   /* handle two cases, not four */
30   if (sa == sb) {
31     /* both positive or both negative */
32     /* add their magnitudes, copy the sign */
33     c->sign = sa;
34     res = s_mp_add (a, b, c);
35   } else {
36     /* one positive, the other negative */
37     /* subtract the one with the greater magnitude from */
38     /* the one of the lesser magnitude.  The result gets */
39     /* the sign of the one with the greater magnitude. */
40     if (mp_cmp_mag (a, b) == MP_LT) {
41       c->sign = sb;
42       res = s_mp_sub (b, a, c);
43     } else {
44       c->sign = sa;
45       res = s_mp_sub (a, b, c);
46     }
47   }
48   return res;
49 }
50 
51 #endif
52 
53 /* Source: /cvs/libtom/libtommath/bn_mp_add.c,v */
54 /* Revision: 1.4 */
55 /* Date: 2006/12/28 01:25:13 */
56