Bitwise Float To Int

Question

I am trying to figure out the algorithm to this but all I get with google is doing it with casting. I need to know the details.

So if we have a float x and want to return its binary representation what do we need to do?

I know we need to return the float if its NaN or a infinity but otherwise what are the steps?

EDIT

The function takes in an unsigned int, to be used as if it was a float, and then return the integer the number represents. I cannot use casting, just conditionals and bit-wise operators.