I have one employer who has not and will not be able to get me a t4. I want to do my taxes. How do I calculate the amounts that would be in the boxes? (CPP, EI etc)

My previous employer has gone mia. I have filed a complaint but was told to do my taxes in the meantime. How do I calculate all the boxes that would normally be filled on a t4? I have all my paystubs and would like to know how these amounts are calculated based on those numbers.