Subject: Re: [boost] C++ Networking Library Release 0.5
From: Glyn Matthews (glyn.matthews_at_[hidden])
Date: 2010-02-01 06:26:58
Hi Phil and James,
On 31 January 2010 12:08, Phil Endecott <spam_from_boost_dev_at_[hidden]>wrote:
> James Mansion wrote:
>
>> Phil Endecott wrote:
>>
>>> I have an HTTP request parser using Spirit, if you're interested. It is
>>> a bit grotty as I wrote it as my first exercise using Spirit - but it does
>>> work. http://svn.chezphil.org/libpbe/trunk/src/parse_http_request.cc .
>>>
>> Out of interest, is the parser suitable to use as a tutorial on how to
>> translate from RFC specs?
>>
>
> You're welcome to use it in that way if you wish. Most of it was translated
> directly from the BNF in the RFCs.
>
> It also makes the point that almost no-one actually does implement these
> things by taking the BNF, because if you do that it won't work. There is at
> least one bug in the HTTP BNF that is documented on an errata web page
> somewhere (the URL is in my source) but that has never justified a new RFC
> after 11 years...
>
>
> It would be nice to build a library of reference parsers that handle
>> assorted protocols. email is a very interesting one, since the standard (and
>> not-standard-but-in-use) variations on sender, date and time etc are quite
>> tricky, and I guess there is some commonality given that the RFCs tend to
>> reference each other. (Sort of thing I'm thinking of is the comment parts
>> embeddable in dates and the newlines etc).
>>
>
> If you try to parse email headers per the BNF in the RFCs you will fail on
> a huge proportion of it. Somewhere I have a list of all the date formats
> that I have seen; it is ridiculous. I think this is a fundamental problem
> with text-based protocols; the "spec" is not the real spec; the real spec is
> the deployed implementations (see e.g. HTML parsers). Anyway, that's
> off-topic....
>
>
>
I would say that this is on-topic as it is an issue that we face in
implementing cpp-netlib. Currently, the request parser in the HTTP server
is taken from Boost.Asio HTTP example but I'm certain that this can be
improved.
Phil: thank you for your comments, I've added them to our issue tracker:
http://github.com/cpp-netlib/cpp-netlib/issues
If anyone would like to comment on these or add other issues, I'd encourage
you to do so on our mailing list.
Thanks,
Glyn