libtommath/bn_mp_tc_xor.c
2019-04-12 14:55:08 +02:00

78 lines
1.6 KiB
C

#include "tommath_private.h"
#ifdef BN_MP_TC_XOR_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */
/* two complement xor */
int mp_tc_xor(const mp_int *a, const mp_int *b, mp_int *c)
{
int res = MP_OKAY, bits, abits, bbits;
int sa = a->sign, sb = b->sign;
mp_int *mx = NULL, _mx, acpy, bcpy;
if ((sa == MP_NEG) || (sb == MP_NEG)) {
abits = mp_count_bits(a);
bbits = mp_count_bits(b);
bits = MP_MAX(abits, bbits);
res = mp_init_set_int(&_mx, 1uL);
if (res != MP_OKAY) {
goto end;
}
mx = &_mx;
res = mp_mul_2d(mx, bits + 1, mx);
if (res != MP_OKAY) {
goto end;
}
if (sa == MP_NEG) {
res = mp_init(&acpy);
if (res != MP_OKAY) {
goto end;
}
res = mp_add(mx, a, &acpy);
if (res != MP_OKAY) {
mp_clear(&acpy);
goto end;
}
a = &acpy;
}
if (sb == MP_NEG) {
res = mp_init(&bcpy);
if (res != MP_OKAY) {
goto end;
}
res = mp_add(mx, b, &bcpy);
if (res != MP_OKAY) {
mp_clear(&bcpy);
goto end;
}
b = &bcpy;
}
}
res = mp_xor(a, b, c);
if ((((sa == MP_NEG) && (sb != MP_NEG)) || ((sa != MP_NEG) && (sb == MP_NEG))) && (res == MP_OKAY)) {
res = mp_sub(c, mx, c);
}
end:
if (a == &acpy) {
mp_clear(&acpy);
}
if (b == &bcpy) {
mp_clear(&bcpy);
}
if (mx == &_mx) {
mp_clear(mx);
}
return res;
}
#endif