T MP_mod(T z, T x, T y) {
int sx, sy;
assert(x); assert(y); assert(z);
sx = sign(x);
sy = sign(y);
if (sx) {
XP_neg(nbytes, tmp[0], x, 1);
x = tmp[0];
x[nbytes-1] &= msb;
}
if (sy) {
XP_neg(nbytes, tmp[1], y, 1);
y = tmp[1];
y[nbytes-1] &= msb;
} else {
memcpy(tmp[1], y, nbytes);
y = tmp[1];
}
if (!XP_div(nbytes, tmp[2], x, nbytes, y, z, tmp[3]))
RAISE(MP_Dividebyzero);
if (sx != sy) {
if (!iszero(z))
XP_sub(nbytes, z, y, z, 0);
} else if (sx && sign(tmp[2]))
RAISE(MP_Overflow);
return z;
}
T AP_mod(T x, T y) {
T q, r;
assert(x);
assert(y);
assert(!iszero(y));
q = mk(x->ndigits);
r = mk(y->ndigits);
{
XP_T tmp = ALLOC(x->ndigits + y->ndigits + 2);
XP_div(x->ndigits, q->digits, x->digits,
y->ndigits, y->digits, r->digits, tmp);
FREE(tmp);
}
normalize(q, q->size);
normalize(r, r->size);
q->sign = iszero(q)
|| ((x->sign^y->sign) == 0) ? 1 : -1;
if (!((x->sign^y->sign) == 0) && !iszero(r)) {
int borrow = XP_sub(r->size, r->digits,
y->digits, r->digits, 0);
assert(borrow == 0);
normalize(r, r->size);
}
AP_free(&q);
return r;
}
T MP_subu(T z, T x, T y) {
int borrow;
assert(x); assert(y); assert(z);
borrow = XP_sub(nbytes, z, x, y, 0);
borrow |= z[nbytes-1]&~msb;
z[nbytes-1] &= msb;
if (borrow)
RAISE(MP_Overflow);
return z;
}
static T sub(T z, T x, T y) {
int borrow, n = y->ndigits;
borrow = XP_sub(n, z->digits, x->digits,
y->digits, 0);
if (x->ndigits > n)
borrow = XP_diff(x->ndigits - n, &z->digits[n],
&x->digits[n], borrow);
assert(borrow == 0);
return normalize(z, z->size);
}
T MP_sub(T z, T x, T y) {
int sx, sy;
assert(x); assert(y); assert(z);
sx = sign(x);
sy = sign(y);
XP_sub(nbytes, z, x, y, 0);
z[nbytes-1] &= msb;
if (sx != sy && sy == sign(z))
RAISE(MP_Overflow);
return z;
}
