private static void PointLookup(int block, int index, PointPrecomp p)
{
Debug.Assert(0 <= block && block < PrecompBlocks);
Debug.Assert(0 <= index && index < PrecompPoints);
int off = block * PrecompPoints * 3 * X25519Field.Size;
for (int i = 0; i < PrecompPoints; ++i)
{
int cond = ((i ^ index) - 1) >> 31;
X25519Field.CMov(cond, precompBase, off, p.ypx_h, 0); off += X25519Field.Size;
X25519Field.CMov(cond, precompBase, off, p.ymx_h, 0); off += X25519Field.Size;
X25519Field.CMov(cond, precompBase, off, p.xyd, 0); off += X25519Field.Size;
}
}