87 lines
2.4 KiB
C
87 lines
2.4 KiB
C
#include "tommath_private.h"
|
|
#ifdef BN_MP_MUL_C
|
|
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
|
|
/* SPDX-License-Identifier: Unlicense */
|
|
|
|
/* high level multiplication (handles sign) */
|
|
mp_err mp_mul(const mp_int *a, const mp_int *b, mp_int *c)
|
|
{
|
|
mp_err err;
|
|
mp_sign neg;
|
|
#ifdef BN_S_MP_BALANCE_MUL_C
|
|
int len_b, len_a;
|
|
#endif
|
|
neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
|
|
#ifdef BN_S_MP_BALANCE_MUL_C
|
|
len_a = a->used;
|
|
len_b = b->used;
|
|
|
|
if (len_a == len_b) {
|
|
goto GO_ON;
|
|
}
|
|
/*
|
|
* Check sizes. The smaller one needs to be larger than the Karatsuba cut-off.
|
|
* The bigger one needs to be at least about one KARATSUBA_MUL_CUTOFF bigger
|
|
* to make some sense, but it depends on architecture, OS, position of the
|
|
* stars... so YMMV.
|
|
* Using it to cut the input into slices small enough for fast_s_mp_mul_digs
|
|
* was actually slower on the author's machine, but YMMV.
|
|
*/
|
|
if ((MP_MIN(len_a, len_b) < MP_KARATSUBA_MUL_CUTOFF)
|
|
|| ((MP_MAX(len_a, len_b) / 2) < MP_KARATSUBA_MUL_CUTOFF)) {
|
|
goto GO_ON;
|
|
}
|
|
/*
|
|
* Not much effect was observed below a ratio of 1:2, but again: YMMV.
|
|
*/
|
|
if ((MP_MAX(len_a, len_b) / MP_MIN(len_a, len_b)) < 2) {
|
|
goto GO_ON;
|
|
}
|
|
|
|
err = s_mp_balance_mul(a,b,c);
|
|
goto END;
|
|
|
|
GO_ON:
|
|
#endif
|
|
|
|
/* use Toom-Cook? */
|
|
#ifdef BN_S_MP_TOOM_MUL_C
|
|
if (MP_MIN(a->used, b->used) >= MP_TOOM_MUL_CUTOFF) {
|
|
err = s_mp_toom_mul(a, b, c);
|
|
} else
|
|
#endif
|
|
#ifdef BN_S_MP_KARATSUBA_MUL_C
|
|
/* use Karatsuba? */
|
|
if (MP_MIN(a->used, b->used) >= MP_KARATSUBA_MUL_CUTOFF) {
|
|
err = s_mp_karatsuba_mul(a, b, c);
|
|
} else
|
|
#endif
|
|
{
|
|
/* can we use the fast multiplier?
|
|
*
|
|
* The fast multiplier can be used if the output will
|
|
* have less than MP_WARRAY digits and the number of
|
|
* digits won't affect carry propagation
|
|
*/
|
|
int digs = a->used + b->used + 1;
|
|
|
|
#ifdef BN_S_MP_MUL_DIGS_FAST_C
|
|
if ((digs < (int)MP_WARRAY) &&
|
|
(MP_MIN(a->used, b->used) <= MP_MAXFAST)) {
|
|
err = s_mp_mul_digs_fast(a, b, c, digs);
|
|
} else
|
|
#endif
|
|
{
|
|
#ifdef BN_S_MP_MUL_DIGS_C
|
|
err = s_mp_mul_digs(a, b, c, a->used + b->used + 1);
|
|
#else
|
|
err = MP_VAL;
|
|
#endif
|
|
}
|
|
}
|
|
END:
|
|
c->sign = (c->used > 0) ? neg : MP_ZPOS;
|
|
return err;
|
|
}
|
|
#endif
|