68 lines
1.9 KiB
C
68 lines
1.9 KiB
C
#include <tommath_private.h>
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#ifdef BN_MP_MUL_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, tstdenis82@gmail.com, http://libtom.org
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*/
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/* high level multiplication (handles sign) */
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int mp_mul(const mp_int *a, const mp_int *b, mp_int *c)
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{
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int res, neg;
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neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
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/* use Toom-Cook? */
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#ifdef BN_MP_TOOM_MUL_C
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if (MIN(a->used, b->used) >= TOOM_MUL_CUTOFF) {
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res = mp_toom_mul(a, b, c);
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} else
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#endif
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#ifdef BN_MP_KARATSUBA_MUL_C
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/* use Karatsuba? */
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if (MIN(a->used, b->used) >= KARATSUBA_MUL_CUTOFF) {
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res = mp_karatsuba_mul(a, b, c);
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} else
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#endif
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{
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/* can we use the fast multiplier?
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*
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* The fast multiplier can be used if the output will
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* have less than MP_WARRAY digits and the number of
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* digits won't affect carry propagation
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*/
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int digs = a->used + b->used + 1;
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#ifdef BN_FAST_S_MP_MUL_DIGS_C
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if ((digs < (int)MP_WARRAY) &&
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(MIN(a->used, b->used) <=
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(int)(1u << (((size_t)CHAR_BIT * sizeof(mp_word)) - (2u * (size_t)DIGIT_BIT))))) {
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res = fast_s_mp_mul_digs(a, b, c, digs);
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} else
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#endif
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{
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#ifdef BN_S_MP_MUL_DIGS_C
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res = s_mp_mul(a, b, c); /* uses s_mp_mul_digs */
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#else
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res = MP_VAL;
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#endif
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}
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}
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c->sign = (c->used > 0) ? neg : MP_ZPOS;
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return res;
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}
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#endif
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/* ref: $Format:%D$ */
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/* git commit: $Format:%H$ */
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/* commit time: $Format:%ai$ */
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