Measuring rotor position by using quad encoder

I am doing a project on designing an AC drive for 30hp induction motor. For this we are using controller board from Texas TMS320f2812. For this I am selecting 1 encoder.

After selecting quad encoder, 3 pulses coming from encoder 2 are for measuring speed, and 1 is for position. I have 1 question.

How do we measure the postion of the rotor by using quadrature encoder after getting the index signal?
How can we give this signal to the DSP?
How will it measure the position of the rotor?
also speed of the motor...

Plz post the answer to my mail id.

Thanks in advance,
rameshkumar143 @ gmail. com