Re-export HTTP parsers

[lllama]

This change reverses 299cf84. Having HTTP parsers exported is useful when needing to debug HTTP connections (accessing raw buffers in particular). An example usage can be found here: http://miensol.pl/2014/03/23/nonintrusive-http-proxy-in-nodejs.html

NB: Commit message for 299cf84 mentions that a different name might be needed, as changes to the parsers' lifecycle may break existing usage.

[vkurchatkin]

-1. it should stay private

[ghost]

I think it should be a configuration choice which defaults to not exporting.

[lllama]

The use case for this is to enable access to the raw HTTP messages, which are currently cleared when requests or responses have been parsed. Not being able to access the parsers seems to mean that accessing the messages will require passing connections through a raw socket (to buffer the messages ourselves) or reimplement our own parsers (which seems redundant given that there are robust parsers available).

Is my understanding correct? (quite possible that I'm completely wrong).

[bnoordhuis]

@lllama I may be misunderstanding the use case but if you want the raw messages, can't you listen for 'data' events on the socket?

[lllama]

@bnoordhuis Listening on the "data" event will allow us to buffer the raw data but we will not be able to easily marry this up to a request object. e.g. if two requests are sent on the same socket then we will need to be able to reliably split them and associate them with the actual request object that we get from the "request" event.

[bnoordhuis]

@lllama Okay, I think I get it now but after reading the article you linked to, I think I agree with @vkurchatkin that it's better if the parser list stays hidden.

The implementation details changed quite a bit since that article was written and will almost certainly change again. There is no promise of API stability; if you use parsers in your own code, you'll sooner or later end up shooting yourself in the foot.

If you really want to, you can use process.binding('http_parser').HTTPParser but you're probably better off using a module like https://github.com/creationix/http-parser-js.

[cjihrig]

I'm going to close this for now.

[lllama]

Thanks for the quick feedback on this PR. Very much appreciated.