39 lines
1008 B
C
39 lines
1008 B
C
#include "tommath_private.h"
|
|
#ifdef BN_MP_ADD_C
|
|
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
|
|
/* SPDX-License-Identifier: Unlicense */
|
|
|
|
/* high level addition (handles signs) */
|
|
mp_err mp_add(const mp_int *a, const mp_int *b, mp_int *c)
|
|
{
|
|
mp_sign sa, sb;
|
|
mp_err err;
|
|
|
|
/* 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;
|
|
err = 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;
|
|
err = s_mp_sub(b, a, c);
|
|
} else {
|
|
c->sign = sa;
|
|
err = s_mp_sub(a, b, c);
|
|
}
|
|
}
|
|
return err;
|
|
}
|
|
|
|
#endif
|