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 (at) gmail.com, http://math.libtomcrypt.com 16 */ 17 18 /* high level addition (handles signs) */ 19 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 sa = a->sign; 25 sb = b->sign; 26 27 /* handle two cases, not four */ 28 if (sa == sb) { 29 /* both positive or both negative */ 30 /* add their magnitudes, copy the sign */ 31 c->sign = sa; 32 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 if (mp_cmp_mag (a, b) == MP_LT) { 39 c->sign = sb; 40 res = s_mp_sub (b, a, c); 41 } else { 42 c->sign = sa; 43 res = s_mp_sub (a, b, c); 44 } 45 } 46 return res; 47 } 48 49 #endif 50 51 /* $Source: /cvs/libtom/libtommath/bn_mp_add.c,v $ */ 52 /* $Revision: 1.3 $ */ 53 /* $Date: 2006/03/31 14:18:44 $ */ 54
