Add CORS parsing/building functions

[manifest]

Part of the Cowboy's feature 947 "Make Cowboy CORS friendly". If those changes are ok, I will update Cowboy's PR.

[essen]

On the interface side of things, two comments: http|https should really be <<"http">> and <<"https">> because that's what we'll have on the Cowboy side of things (either are fine technically, just keeping binary because that's what we get and we don't match too often on them).

Then the reference I don't understand.

On the tests: Cowboy will never send input with trailing whitespace. It's cut off beforehand. That's why parse_host does a binary_to_integer directly, because at that point we can only have numbers or the input is invalid and we crash.

On implementation: don't modify parse_host to attempt to reuse it. This most likely made it slower for no good reason. This module repeats itself a lot, there's no attempt at avoiding that, there's a large attempt at making the code as fast as possible instead. I'd expect parse_origin to have much of the same code as parse_host, except with extra scheme and list handling.

[manifest]

According to the RFC we should generate a fresh globally unique identifier and return that value in the cases:

• URI does not use a hierarchical element as a naming authority or if the URI is not an absolute URI
• the implementation doesn't support the protocol given by uri-scheme

So, reference represents a guid here.
Also a CORS implementation needs some representation of the origin even we didn't fully recognize it. It needs something that could be compared with an allowed origins list or "*". Thus, we're parsing an "origin" header, getting a reference, comparing it with "*" and returning the "access-control-allow-origin" header with the value "*". If we failed on parsing origin, we couldn't provide a resource allowed for all.

As for the tests and implementation I got it and will fix that.

[essen]

Fair enough. But this should be written somewhere. :-)

[manifest]

Ready.

[essen]

That looks very good, best PR in a long time. I don't have any further comments. It looks ready to merge, perhaps tomorrow if time allows. Thanks!

[manifest]

Thanks! I will make a few more soon. :-)

[manifest]

I've just added other commits to this branch.

[manifest]

Probably, we should rename these fuctions:

access_control_allow{headers,methods}
parse_access_controlallow{headers,methods}
access_controlexposeheaders
parse_access_controlexpose_headers

to

access_control_allowed{headers,methods}
parse_access_controlallowed{headers,methods}
access_controlexposedheaders
parse_access_controlexposed_headers

They will sound more natural, I think. Shall we?

[essen]

Should be the header name.

[manifest]

The PR is ready then. I've also updated the Cowboy's PR.

[essen]

Yeah I will get back to you before the end of the week hopefully. Today is RabbitMQ day. :-) Thanks!

[manifest]

Looking forward to it :-)

[essen]

I will put a couple notes, if you have time to fix, cool, otherwise just say so and i'll correct in the merge commit.

[essen]

Should put a @todo at the beginning of this line to not forget.

[essen]

Think that's it.

[manifest]

I will have done it by the end of this day.

[manifest]

It's ready.

[essen]

Thanks. I'll be on it tomorrow.

[essen]

Merged, thanks!