/* Line function */
public static FP12 line(ECP2 A, ECP2 B, FP Qx, FP Qy)
{
ECP2 P = new ECP2();
FP4 a, b, c;
P.copy(A);
FP2 ZZ = new FP2(P.getz());
ZZ.sqr();
int D;
if (A == B)
{
D = A.dbl(); // Check this return value in amcl_ec2.c
}
else
{
D = A.add(B);
}
if (D < 0)
{
return(new FP12(1));
}
FP2 Z3 = new FP2(A.getz());
c = new FP4(0);
if (D == 0)
{ // Addition
FP2 X = new FP2(B.getx());
FP2 Y = new FP2(B.gety());
FP2 T = new FP2(P.getz());
T.mul(Y);
ZZ.mul(T);
FP2 NY = new FP2(P.gety());
NY.neg();
ZZ.add(NY);
Z3.pmul(Qy);
T.mul(P.getx());
X.mul(NY);
T.add(X);
a = new FP4(Z3, T);
ZZ.neg();
ZZ.pmul(Qx);
b = new FP4(ZZ);
}
else
{ // Doubling
FP2 X = new FP2(P.getx());
FP2 Y = new FP2(P.gety());
FP2 T = new FP2(P.getx());
T.sqr();
T.imul(3);
Y.sqr();
Y.add(Y);
Z3.mul(ZZ);
Z3.pmul(Qy);
X.mul(T);
X.sub(Y);
a = new FP4(Z3, X);
T.neg();
ZZ.mul(T);
ZZ.pmul(Qx);
b = new FP4(ZZ);
}
return(new FP12(a, b, c));
}