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39 lines
1008 B
39 lines
1008 B
#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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/* SPDX-License-Identifier: Unlicense */
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/* high level addition (handles signs) */
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mp_err mp_add(const mp_int *a, const mp_int *b, mp_int *c)
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{
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mp_sign sa, sb;
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mp_err err;
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/* get sign of both inputs */
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sa = a->sign;
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sb = b->sign;
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/* handle two cases, not four */
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if (sa == sb) {
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/* both positive or both negative */
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/* add their magnitudes, copy the sign */
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c->sign = sa;
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err = s_mp_add(a, b, c);
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} else {
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/* one positive, the other negative */
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/* subtract the one with the greater magnitude from */
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/* the one of the lesser magnitude. The result gets */
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/* the sign of the one with the greater magnitude. */
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if (mp_cmp_mag(a, b) == MP_LT) {
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c->sign = sb;
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err = s_mp_sub(b, a, c);
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} else {
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c->sign = sa;
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err = s_mp_sub(a, b, c);
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}
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}
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return err;
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}
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#endif
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