long MP_modi(T x, long y) {
assert(x);
if (y == 0)
RAISE(MP_Dividebyzero);
else if (-BASE < y && y < BASE) {
T z = tmp[2];
int r;
int sx = sign(x), sy = y < 0;
if (sx) {
XP_neg(nbytes, tmp[0], x, 1);
x = tmp[0];
x[nbytes-1] &= msb;
}
r = XP_quotient(nbytes, z, x, sy ? -y : y);
if (sx != sy) {
XP_neg(nbytes, z, z, 1);
if (r != 0) {
XP_diff(nbytes, z, z, 1);
r = y - r;
}
z[nbytes-1] &= msb;
} else if (sx && sign(z))
RAISE(MP_Overflow);
if (nbits < 8
&& (y < -(1<<(nbits-1)) || y >= (1<<(nbits-1))))
RAISE(MP_Overflow);
return r;
} else if (apply(MP_mod, tmp[2], x, y))
RAISE(MP_Overflow);
return MP_toint(tmp[2]);
}
T MP_div(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, z, x, nbytes, y, tmp[2], tmp[3]))
RAISE(MP_Dividebyzero);
if (sx != sy) {
XP_neg(nbytes, z, z, 1);
if (!iszero(tmp[2]))
XP_diff(nbytes, z, z, 1);
z[nbytes-1] &= msb;
} else if (sx && sign(z))
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_subui(T z, T x, unsigned long y) {
assert(x); assert(z);
if (y < BASE) {
int borrow = XP_diff(nbytes, z, x, y);
borrow |= z[nbytes-1]&~msb;
z[nbytes-1] &= msb;
if (borrow)
RAISE(MP_Overflow);
} else if (applyu(MP_subu, z, x, y))
RAISE(MP_Overflow);
return z;
}
T MP_subi(T z, T x, long y) {
assert(x); assert(z);
if (-BASE < y && y < BASE) {
int sx = sign(x), sy = y < 0;
if (sy)
XP_sum (nbytes, z, x, -y);
else
XP_diff(nbytes, z, x, y);
z[nbytes-1] &= msb;
if (sx != sy && sy == sign(z))
RAISE(MP_Overflow);
if (nbits < 8
&& (y < -(1<<(nbits-1)) || y >= (1<<(nbits-1))))
RAISE(MP_Overflow);
} else if (apply(MP_sub, z, x, y))
RAISE(MP_Overflow);
return z;
}
