Line data Source code
1 : #include <tommath.h>
2 : #ifdef BN_MP_ADD_C
3 : /* LibTomMath, multiple-precision integer library -- Tom St Denis
4 : *
5 : * LibTomMath is a library that provides multiple-precision
6 : * integer arithmetic as well as number theoretic functionality.
7 : *
8 : * The library was designed directly after the MPI library by
9 : * Michael Fromberger but has been written from scratch with
10 : * additional optimizations in place.
11 : *
12 : * The library is free for all purposes without any express
13 : * guarantee it works.
14 : *
15 : * Tom St Denis, tomstdenis@gmail.com, http://libtom.org
16 : */
17 :
18 : /* high level addition (handles signs) */
19 7081 : int mp_add (mp_int * a, mp_int * b, mp_int * c)
20 : {
21 : int sa, sb, res;
22 :
23 : /* get sign of both inputs */
24 7081 : sa = a->sign;
25 7081 : sb = b->sign;
26 :
27 : /* handle two cases, not four */
28 7081 : if (sa == sb) {
29 : /* both positive or both negative */
30 : /* add their magnitudes, copy the sign */
31 6880 : c->sign = sa;
32 6880 : res = s_mp_add (a, b, c);
33 : } else {
34 : /* one positive, the other negative */
35 : /* subtract the one with the greater magnitude from */
36 : /* the one of the lesser magnitude. The result gets */
37 : /* the sign of the one with the greater magnitude. */
38 201 : if (mp_cmp_mag (a, b) == MP_LT) {
39 201 : c->sign = sb;
40 201 : res = s_mp_sub (b, a, c);
41 : } else {
42 0 : c->sign = sa;
43 0 : res = s_mp_sub (a, b, c);
44 : }
45 : }
46 7081 : return res;
47 : }
48 :
49 : #endif
50 :
51 : /* $Source: /cvs/libtom/libtommath/bn_mp_add.c,v $ */
52 : /* $Revision: 1.4 $ */
53 : /* $Date: 2006/12/28 01:25:13 $ */
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