libtommath/mp_or.c
2019-11-11 21:52:20 +01:00

55 lines
1.3 KiB
C

#include "tommath_private.h"
#ifdef MP_OR_C
/* LibTomMath, multiple-precision integer library -- Tom St Denis */
/* SPDX-License-Identifier: Unlicense */
/* two complement or */
mp_err mp_or(const mp_int *a, const mp_int *b, mp_int *c)
{
int used = MP_MAX(a->used, b->used) + 1, i;
mp_err err;
mp_digit ac = 1, bc = 1, cc = 1;
bool neg = (mp_isneg(a) || mp_isneg(b));
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 (mp_isneg(a)) {
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 (mp_isneg(b)) {
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 (neg) {
cc += ~c->dp[i] & MP_MASK;
c->dp[i] = cc & MP_MASK;
cc >>= MP_DIGIT_BIT;
}
}
c->used = used;
c->sign = (neg ? MP_NEG : MP_ZPOS);
mp_clamp(c);
return MP_OKAY;
}
#endif