Stateful pointers in set-returning functions

Hi,

I'm writing a set-returning function which places a file handle into
PG's FuncCallContext's user_fctx space. My problem is that when the
function is ran with a limit clause (SELECT * FROM foo() LIMIT 10) the
server will stop calling the function automatically, not giving me a
chance to close the file handle. Is there a way to get the limit value
inside of foo() and set the max max_calls parameter correctly?

Thanks,

Ian