/**
* Multiplies two binary field elements using right-to-left comb multiplication.
*
* @param c - the result.
* @param a - the first binary field element.
* @param b - the second binary field element.
* @param size - the number of digits to multiply.
*/
static void fb_mul_rcomb_imp(dig_t *c, const dig_t *a, const dig_t *b, int size) {
dv_t _b;
dv_null(_b);
TRY {
dv_new(_b);
dv_zero(c, 2 * size);
for (int i = 0; i < size; i++)
_b[i] = b[i];
_b[size] = 0;
for (int i = 0; i < FB_DIGIT; i++) {
for (int j = 0; j < size; j++) {
if (a[j] & ((dig_t)1 << i)) {
fb_addd_low(c + j, c + j, _b, size + 1);
}
}
if (i != FB_DIGIT - 1) {
bn_lsh1_low(_b, _b, size + 1);
}
}
}
CATCH_ANY {
THROW(ERR_CAUGHT);
}
FINALLY {
dv_free(_b);
}
}
/**
* Multiplies two binary field elements using left-to-right comb multiplication.
*
* @param c - the result.
* @param a - the first binary field element.
* @param b - the second binary field element.
* @param size - the number of digits to multiply.
*/
static void fb_mul_lcomb_imp(dig_t *c, const dig_t *a, const dig_t *b, int size) {
dv_zero(c, 2 * size);
for (int i = FB_DIGIT - 1; i >= 0; i--) {
for (int j = 0; j < size; j++) {
if (a[j] & ((dig_t)1 << i)) {
fb_addd_low(c + j, c + j, b, size);
}
}
if (i != 0) {
bn_lsh1_low(c, c, 2 * size);
}
}
}
void bn_dbl(bn_t c, bn_t a) {
dig_t carry;
bn_grow(c, a->used + 1);
c->used = a->used;
carry = bn_lsh1_low(c->dp, a->dp, c->used);
/* If there is an additional carry. */
if (carry != 0) {
c->dp[c->used] = carry;
(c->used)++;
}
c->sign = a->sign;
}
