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      1 /*	$NetBSD: bn_mp_add.c,v 1.2 2017/01/28 21:31:47 christos 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 (at) 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