79 lines
1.9 KiB
C
79 lines
1.9 KiB
C
|
#include "tommath_private.h"
|
||
|
|
#ifdef BN_MP_BALANCE_MUL_C
|
||
|
|
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
|
||
|
|
/* SPDX-License-Identifier: Unlicense */
|
||
|
|
|
||
|
|
/* single-digit multiplication with the smaller number as the single-digit */
|
||
|
|
int mp_balance_mul(const mp_int *a, const mp_int *b, mp_int *c)
|
||
|
|
{
|
||
|
|
int e, count, len_a, len_b, nblocks, i, j, bsize;
|
||
|
|
mp_int a0, tmp, A, B, r;
|
||
|
|
|
||
|
|
len_a = a->used;
|
||
|
|
len_b = b->used;
|
||
|
|
|
||
|
|
nblocks = MAX(a->used, b->used) / MIN(a->used, b->used);
|
||
|
|
bsize = MIN(a->used, b->used) ;
|
||
|
|
|
||
|
|
if ((e = mp_init_size(&a0, bsize + 2)) != MP_OKAY) {
|
||
|
|
return e;
|
||
|
|
}
|
||
|
|
if ((e = mp_init_multi(&tmp, &r, NULL)) != MP_OKAY) {
|
||
|
|
mp_clear(&a0);
|
||
|
|
return e;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Make sure that A is the larger one*/
|
||
|
|
if (len_a < len_b) {
|
||
|
|
B = *a;
|
||
|
|
A = *b;
|
||
|
|
} else {
|
||
|
|
A = *a;
|
||
|
|
B = *b;
|
||
|
|
}
|
||
|
|
|
||
|
|
for (i = 0, j=0; i < nblocks; i++) {
|
||
|
|
/* Cut a slice off of a */
|
||
|
|
a0.used = 0;
|
||
|
|
for (count = 0; count < bsize; count++) {
|
||
|
|
a0.dp[count] = A.dp[ j++ ];
|
||
|
|
a0.used++;
|
||
|
|
}
|
||
|
|
/* Multiply with b */
|
||
|
|
if ((e = mp_mul(&a0, &B, &tmp)) != MP_OKAY) {
|
||
|
|
goto LBL_ERR;
|
||
|
|
}
|
||
|
|
/* Shift tmp to the correct position */
|
||
|
|
if ((e = mp_lshd(&tmp, bsize * i)) != MP_OKAY) {
|
||
|
|
goto LBL_ERR;
|
||
|
|
}
|
||
|
|
/* Add to output. No carry needed */
|
||
|
|
if ((e = mp_add(&r, &tmp, &r)) != MP_OKAY) {
|
||
|
|
goto LBL_ERR;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
/* The left-overs; there are always left-overs */
|
||
|
|
if (j < A.used) {
|
||
|
|
a0.used = 0;
|
||
|
|
for (count = 0; j < A.used; count++) {
|
||
|
|
a0.dp[count] = A.dp[ j++ ];
|
||
|
|
a0.used++;
|
||
|
|
}
|
||
|
|
if ((e = mp_mul(&a0, &B, &tmp)) != MP_OKAY) {
|
||
|
|
goto LBL_ERR;
|
||
|
|
}
|
||
|
|
if ((e = mp_lshd(&tmp, bsize * i)) != MP_OKAY) {
|
||
|
|
goto LBL_ERR;
|
||
|
|
}
|
||
|
|
if ((e = mp_add(&r, &tmp, &r)) != MP_OKAY) {
|
||
|
|
goto LBL_ERR;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
mp_exch(&r,c);
|
||
|
|
LBL_ERR:
|
||
|
|
mp_clear_multi(&a0, &tmp, &r,NULL);
|
||
|
|
return e;
|
||
|
|
}
|
||
|
|
#endif
|