Most efficient way for libPQ .. PGresult serialization

I was trying to implement a middleware that lies between client and postgres.

So, this middleware is supposed to run query with libpq, do its job on them, and then serialize the result of query, and send it to the client ! (client deserializes to PGresult)

I could simply iterate over rows and columns but than that would be slow.

I also found that query results consist of 3 parts (PGresult, tuples, data blocks).

Could I please get some pointers ? :)

Thanks,

Joshua