Buffered reading in LuaSocket..

[Duck <duck@...>]

G'day folks. I want to combine the functionality of tcp:receive(number) 
[i.e. receive number bytes of data]  and tcp:receive('*l') [i.e. read the 
next line, delimited by LF].

I want to be able to write a line-oriented TCP server (e.g. SMTP) without 
being at the whim of the connecting client when it comes to line length. 

How to do this (using blocking) in Lua?

How do I say "read up to Y bytes or the next LF character, whichever 
comes first, with a timeout of X seconds" without having to wait for 
the timeout to elapse before my tcp:receive() returns with partial data?

Would it be satisfactory to do something like this:

   X = 5; Y = 1000

   tcp:settimeout(X)
   head = tcp:receive(1)
   tcp:settimeout(0)
   tail = tcp:receive(Y-1)

thus assuming that in a line-based protocol with short lines, each line 
tends to become readable at once? Or would something more esoteric be 
required/desired, such as two one-byte reads each using up half of the 
timeout, followed by a "get what's left in one go?"

All advice gladly accepted.