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50 lines
1.3 KiB
C
50 lines
1.3 KiB
C
#include <tommath.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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*
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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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*
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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
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* additional optimizations in place.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*
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* Tom St Denis, tomstdenis@iahu.ca, http://math.libtomcrypt.org
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*/
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/* high level addition (handles signs) */
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int mp_add (mp_int * a, 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 */
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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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res = 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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res = s_mp_sub (b, a, c);
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} else {
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c->sign = sa;
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res = s_mp_sub (a, b, c);
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}
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}
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return res;
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}
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#endif
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