tommath/bn_mp_add.c

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#include "tommath_private.h"
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#ifdef BN_MP_ADD_C
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/* LibTomMath, multiple-precision integer library -- Tom St Denis
*
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* LibTomMath is a library that provides multiple-precision
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* integer arithmetic as well as number theoretic functionality.
*
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* The library was designed directly after the MPI library by
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* 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.
*/
/* high level addition (handles signs) */
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int mp_add(const mp_int *a, const mp_int *b, mp_int *c)
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{
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int sa, sb, res;
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/* get sign of both inputs */
sa = a->sign;
sb = b->sign;
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/* handle two cases, not four */
if (sa == sb) {
/* both positive or both negative */
/* add their magnitudes, copy the sign */
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c->sign = sa;
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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;
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}
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#endif
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/* ref: $Format:%D$ */
/* git commit: $Format:%H$ */
/* commit time: $Format:%ai$ */