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Diffstat (limited to 'libtommath/bn_mp_add.c')
| -rw-r--r-- | libtommath/bn_mp_add.c | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/libtommath/bn_mp_add.c b/libtommath/bn_mp_add.c new file mode 100644 index 0000000..a90eef6 --- /dev/null +++ b/libtommath/bn_mp_add.c @@ -0,0 +1,53 @@ +#include <tommath.h> +#ifdef BN_MP_ADD_C +/* LibTomMath, multiple-precision integer library -- Tom St Denis + * + * LibTomMath is a library that provides multiple-precision + * integer arithmetic as well as number theoretic functionality. + * + * The library was designed directly after the MPI library by + * Michael Fromberger but has been written from scratch with + * additional optimizations in place. + * + * The library is free for all purposes without any express + * guarantee it works. + * + * Tom St Denis, tomstdenis@gmail.com, http://math.libtomcrypt.com + */ + +/* high level addition (handles signs) */ +int mp_add (mp_int * a, mp_int * b, mp_int * c) +{ + int sa, sb, res; + + /* get sign of both inputs */ + sa = a->sign; + sb = b->sign; + + /* handle two cases, not four */ + if (sa == sb) { + /* both positive or both negative */ + /* add their magnitudes, copy the sign */ + c->sign = sa; + res = s_mp_add (a, b, c); + } else { + /* one positive, the other negative */ + /* subtract the one with the greater magnitude from */ + /* the one of the lesser magnitude. The result gets */ + /* the sign of the one with the greater magnitude. */ + if (mp_cmp_mag (a, b) == MP_LT) { + c->sign = sb; + res = s_mp_sub (b, a, c); + } else { + c->sign = sa; + res = s_mp_sub (a, b, c); + } + } + return res; +} + +#endif + +/* $Source: /cvs/libtom/libtommath/bn_mp_add.c,v $ */ +/* $Revision: 1.3 $ */ +/* $Date: 2006/03/31 14:18:44 $ */ |