[boost] Asio, run-time polymorphism

From: stas garifulin (s.garifulin_at_[hidden])
Date: 2006-02-20 09:13:40

Hello.

I have some experience with http protocol and i have question/suggestion 
about implementing this protocol using asio library.

Http/1.1 supports "protocol upgrades": during persistent connection 
client ot server can ask remote peer to upgrade protocol (push 
additional protocol(s) in protocol stack just before HTTP). After 
successful upgrading client can continue to send http-requests to server 
over new protocol stack.
See "Upgrading to TLS Within HTTP/1.1" 
(http://www.faqs.org/rfcs/rfc2817.html) for examples.

Currently asio doesn't allow me to implement this facility (to transform 
socket using simple transport protocol, like TCP, to SSL-socket in 
run-time).

Another problem. HTTP/1.1 supports transfer-encoded bodies of packets, 
i.e. bodies transformed for transmission between sender and recipient 
(compressed, chunked etc.). Such transfer-encoded bodies are always 
chunked, splitted to chunks, each chunk have header with his size, zero 
sized chunk signals end of body.
In some step of my program i would like to eliminate difference between 
plain bodies (reading/writing to socket) and transfer-encoded bodies 
(reading/writing to chain of filters).

In other words i'm talking about some infrastructure like 
boost::iostreams but built on top of asio dispatcher. Async analogue of 
boost::iostreams which allows me to create async chains of filters in 
run-time. For example, it can be done with non-templated versions of 
functions async_read, async_write, handler parameter of this functions 
will have type like boost::function<void (asio::error, size_T)>.
SSL class could be implemented as such async filter and would allow 
attaching at run-time.