1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
|
#include "tommath_private.h"
#ifdef S_MP_DIV_SMALL_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */
/* slower bit-bang division... also smaller */
mp_err s_mp_div_small(const mp_int *a, const mp_int *b, mp_int *c, mp_int *d)
{
mp_int ta, tb, tq, q;
int n;
bool neg;
mp_err err;
/* init our temps */
if ((err = mp_init_multi(&ta, &tb, &tq, &q, NULL)) != MP_OKAY) {
return err;
}
mp_set(&tq, 1uL);
n = mp_count_bits(a) - mp_count_bits(b);
if ((err = mp_abs(a, &ta)) != MP_OKAY) goto LBL_ERR;
if ((err = mp_abs(b, &tb)) != MP_OKAY) goto LBL_ERR;
if ((err = mp_mul_2d(&tb, n, &tb)) != MP_OKAY) goto LBL_ERR;
if ((err = mp_mul_2d(&tq, n, &tq)) != MP_OKAY) goto LBL_ERR;
while (n-- >= 0) {
if (mp_cmp(&tb, &ta) != MP_GT) {
if ((err = mp_sub(&ta, &tb, &ta)) != MP_OKAY) goto LBL_ERR;
if ((err = mp_add(&q, &tq, &q)) != MP_OKAY) goto LBL_ERR;
}
if ((err = mp_div_2d(&tb, 1, &tb, NULL)) != MP_OKAY) goto LBL_ERR;
if ((err = mp_div_2d(&tq, 1, &tq, NULL)) != MP_OKAY) goto LBL_ERR;
}
/* now q == quotient and ta == remainder */
neg = (a->sign != b->sign);
if (c != NULL) {
mp_exch(c, &q);
c->sign = ((neg && !mp_iszero(c)) ? MP_NEG : MP_ZPOS);
}
if (d != NULL) {
mp_exch(d, &ta);
d->sign = (mp_iszero(d) ? MP_ZPOS : a->sign);
}
LBL_ERR:
mp_clear_multi(&ta, &tb, &tq, &q, NULL);
return err;
}
#endif
|
