blob: 073985e092eedbeb467c0a40e621f729556a794f (
plain)
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
52
53
54
55
56
|
#include "tommath_private.h"
#ifdef BN_MP_XOR_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */
/* two complement xor */
mp_err mp_xor(const mp_int *a, const mp_int *b, mp_int *c)
{
int used = MAX(a->used, b->used) + 1, i;
mp_err err;
mp_digit ac = 1, bc = 1, cc = 1;
mp_sign csign = (a->sign != b->sign) ? MP_NEG : MP_ZPOS;
if (c->alloc < used) {
if ((err = mp_grow(c, used)) != MP_OKAY) {
return err;
}
}
for (i = 0; i < used; i++) {
mp_digit x, y;
/* convert to two complement if negative */
if (a->sign == MP_NEG) {
ac += (i >= a->used) ? MP_MASK : (~a->dp[i] & MP_MASK);
x = ac & MP_MASK;
ac >>= MP_DIGIT_BIT;
} else {
x = (i >= a->used) ? 0uL : a->dp[i];
}
/* convert to two complement if negative */
if (b->sign == MP_NEG) {
bc += (i >= b->used) ? MP_MASK : (~b->dp[i] & MP_MASK);
y = bc & MP_MASK;
bc >>= MP_DIGIT_BIT;
} else {
y = (i >= b->used) ? 0uL : b->dp[i];
}
c->dp[i] = x ^ y;
/* convert to to sign-magnitude if negative */
if (csign == MP_NEG) {
cc += ~c->dp[i] & MP_MASK;
c->dp[i] = cc & MP_MASK;
cc >>= MP_DIGIT_BIT;
}
}
c->used = used;
c->sign = csign;
mp_clamp(c);
return MP_OKAY;
}
#endif
|
