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
|
/* See LICENSE file for copyright and license details. */
#include "internals"
#include <errno.h>
#define tb libzahl_tmp_pow_b
#define tc libzahl_tmp_pow_c
#define td libzahl_tmp_pow_d
void
zmodpow(z_t a, z_t b, z_t c, z_t d)
{
size_t i, n;
if (zsignum(c) <= 0) {
if (zzero(c)) {
if (zzero(b)) {
errno = EDOM; /* Indeterminate form: 0:th power of 0 */
FAILURE_JUMP();
}
zsetu(a, 1);
} else if (zzero(b) || zzero(d)) {
errno = EDOM; /* Undefined form: Division by 0 */
FAILURE_JUMP();
} else {
SET_SIGNUM(a, 0);
}
return;
} else if (zzero(d)) {
errno = EDOM; /* Undefined form: Division by 0 */
FAILURE_JUMP();
} else if (zzero(b)) {
SET_SIGNUM(a, 0);
return;
}
n = zbits(c);
zmod(tb, b, d);
zset(tc, c);
zset(td, d);
zsetu(a, 1);
for (i = 0; i < n; i++) {
if (zbtest(tc, i))
zmodmul(a, a, tb, td);
zmodsqr(tb, tb, td);
}
}
|
