Re: [Boost-users] Regular expression min match length

From: John Maddock (john_at_[hidden])
Date: 2007-08-13 12:32:29

Raffaele Romito wrote:
> Thanks for the reply John, I'll try to expose my "use case" with the
> hope this feature will be available in the future...
> I'm developing a system that detects TCP streams with a pattern
> matching, here is the pseudo code  (in a simplified form) of the
> function I'd link to extend:
>
> protocol_stream decodeStream(tcp_stream)
> {
>     foreach(registered protocol in the system)
>     {
>         required_size_to_match =
> calc_min_regex_len(current_protocol.regex);
>
>         if(tcp_stream.buffer_size <= required_size_to_match)
>             check if tcp_stream.buffer matches
>         else
>             try to read from tcp_stream if data is available until
> <required_size_to_match> and check again if matches
>     }
> }
>
> Hope u can help since you have "an almost pathological interest in
> anything that can't be done" :)

Oh dear, I should have realised that this would come back to haunt me ! :-0

I've now realised that in the general case this can't in fact be implemented 
(think back-references), but can be for at least a subset of regexes.  If 
you're still keen on the feature can you please file a feature request on 
the TRAC (http://svn.boost.org/trac) so this doesn't get lost?

Thanks, John.