[boost] Re: Yet Another Network Library

From: David Abrahams (dave_at_[hidden])
Date: 2005-04-24 07:08:40

"Giovanni P. Deretta" <lordshoo_at_[hidden]> writes:

> I've have seen that the current consens is to encode the the stream type 
>  in the address, so to allow a dynamic behaviour: the actual transport 
> is    selected only at runtime, based on the address string. 

Yeah, a similar unfortunate line of thinking seems to prevail in the
discussion of Unicode libraries.

> I think this is a bad decision (i considered doing it while
> implementing my library) and this is why:
>
> - C++ is a static language, let's leave these niceties to more dynamic 
> languages.  I have found myself weeks hunting a bug in the http code 
> because i thought that it would be cool if i could access http 
> properties using a map instead of proper accessor functions. I spent 
> weeks hunting persistent connection bug. It was a simple typo inside a 
> http property string that would have been caught immediately by the 
> compiler if i were using functions or costants [1].

Right.  If you need to do dynamic polymorphism, add a layer of type
erasure in a separate component.  I think that's what you meant by
"external polymorphism," but that's not a great term because it
doesn't distinguish the static from the dynamic.

> - It mimics standard library usage.  You cannot open the input stream 
> instead of a file by using the "input:" file name. (well under Unix you 
> might actually do it, but i don't think this was the intention of the 
> standard library authors and it is not portable any way).
>
> - It is extremely insecure.  In a network library security must be 
> paramount.  If the transport type were encoded in the address, it would 
> be much harder to validate externally received addresses.  A similar 
> argument can be made for the port numbers. It is better to keep these 
> things separated.  The library user can create its own indexed factory 
> collection if it really needs to.

That's a very convincing argument.

I don't know much about networking, but from what I've heard here I
like your design instincts very much.  I'll try to look at your docs.
Is this in the same design space as a "sockets library?"

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com