Givens method for sparse matrix

I have to solve a linear equation system, Ax=b, where A is a (very) large sparse matrix (compressed sparse column form).

From what I've read I think I'm supposed to use Givens method, but I don't know how since A is too big to be stored in memory and all I have are the three vectors (rows, columns and values).

I don't want to use a built-in Matlab function.

For systems too large to fit in memory, the trick is replacing $\mathbf{Ax}$ with $\operatorname{f}(\mathbf{x})$, where $\operatorname{f}$ is a function pointer that will return the matrix-vector product. Of course there is work to be done on your part to write the function, but that's really all there is to it