Streaming XML parsing

[xhochy]

I started work on implementing streaming XML parsing. There is still a lot of work to do but I really would appreciate early feedback so that I can develop in the right direction.

Very basic usage which highlights my current architecture choices:

using LibExpat

cbs = XPCallbacks()
cbs.start_element = function (h, name, attrs)
    @printf("Found start tag: %s\n", name)
end

xp_streaming_parse("<t>t</t>", cbs)

[xhochy]

• Included small documentation in the README
• Added a test set for the majority of callbacks
• Provided all the callbacks which are also used by the ETree parsing process

I'm now at the stage where I think this PR is for final review/merge. If it gets accepted I'd work on migrating the ETree parsing process to this streaming backend to avoid further code duplication.

[amitmurthy]

I am OK with merging this. Could you rebase and squash your commits?

@vtjnash comments?

[xhochy]

Squash, rebased and added the missing xml test file

[vtjnash]

seems like a good idea to me. the only thing i would suggest is shortening the method names by removing xp and streaming. In C, these are needed to distinguish the method call, but in Julia, they just makes it harder to have reusable interfaces.

[xhochy]

@vtjnash You mean: renaming xp_streaming_parse to parse?

[vtjnash]

yes, but also parsefile, start, pause, stop, etc

[xhochy]

Removed useless ::Function and xp_streaming_ prefixes

[amitmurthy]

Thanks Jameson. Will merge this in a few hours if there are no more concerns.

[amitmurthy]

And thanks @xhochy for this feature. Do tag and bump the version in METADATA whenever you are ready.