crypto/external/bsd/heimdal/dist/lib/hcrypto/libtommath/bn_mp_add.c

   1 /*      $NetBSD: bn_mp_add.c,v 1.1.1.2 2014/04/24 12:45:31 pettai 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  */