Add PHP-Markdown style footnotes support

[brief]

@djui opened an identical pull request a month ago, but it has stalled. Thought I would submit my own with the requested changes.

This includes the great original work by @bdolman and @adamflorin, a fix to footnote parsing by @microjo, a test case in test/html_render_test.rb, and edits to the changelog and readme.

[robin850]

Very clean and nice pull request! Thanks. @mattr- : Should we merge this one over #241?

However, if we merge this pull request I think we should add the others contributors to the changelog entry.

[mattr-]

I have a few questions:

• Why did you choose to use a linked list for storing footnotes?
• Did you do any testing to verify that you don't have infinite recursion and/or memory leaks in your list implementation?
• Could you add tests for when footnotes are enabled but missing in the document?

Thanks! ❤️

[brief]

I'll defer to @bdolman for the first and second points since it is his code. As for the third, I can add tests for when footnotes are enabled but either the marker or definitions are missing. Anything else?

[olivierlacan]

I assumed this was already supported by redcarpet. Good job @brief, and thanks for the pull request.

[robin850]

It's a detail but I would update this line like this:

if (ob->size) bufputc(ob, '\n');

BUFPUTSL(ob, "<div class=\"footnotes\">\n");
BUFPUTSL(ob, USE_XHTML(options) ? "<hr/>\n" : "<hr>\n");
BUFPUTSL(ob, "<ol>\n");

[robin850]

With that at the very top of the function (sorry forgot about that):

struct html_renderopt *options = opaque;

[robin850]

Hello there,

I've just added a quick comment in the code.

I think we won't get any answer from @bdolman since his last activity was 2 months ago.

@mattr- : What do you think about merging this and see after if we can ensure there is no infinite loop?

[mattr-]

If it's almost good enough, I'd merge it into a separate branch, make any
changes we need to, and then push it back to master.

On Thu, Jul 11, 2013 at 6:43 AM, Robin Dupret notifications@github.comwrote:

Hello there,

I've just added a quick comment in the code.

I think we won't get any answer from @bdolman https://github.com/bdolmansince his last activity was 2 months ago.

@mattr- https://github.com/mattr- : What do you think about merging
this and see after if we can ensure there is no infinite loop?

—
Reply to this email directly or view it on GitHubhttps://github.com//pull/271#issuecomment-20805542
.

[robin850]

@brief : I've noticed that you have updated this PR ; thanks! 😃

@mattr- : I think we are good to merge it into a footnotes branch or whatever. Thank you!

[brief]

Ready to merge?

[mattr-]

@robin850 would you mind merging this? I'm recovering from a conference and most likely won't have time to spend on this for another few days. Thanks!

[bdolman]

Apologies for the delay, here are some answers to earlier questions:

Why did you choose to use a linked list for storing footnotes?

It matches the data structures being used for storing links, which are similar to footnotes. To be completely accurate, links are stored using a very basic hash table predefined to contain at most 8 buckets (I believe it's 8—it's been months since I've looked at the code, but that's my recollection). Footnotes are stored in a single linked list because I didn't feel like I needed something quite as optimized as links and since it was a hardcoded 8 buckets anyway, I just didn't think that 99.9% of the use cases of footnotes would benefit from the additional complexity I'd have to put in the footnotes code.

Did you do any testing to verify that you don't have infinite recursion and/or memory leaks in your list implementation?

I did not, but I have run the Clang static analyzer and fixed any issues I found there. It's also been out in the wild for many, many months on apps with user bases in the millions and we haven't seen any issues.

[mattr-]

awesome! thanks for getting back to us! It's very much appreciated! 😃

[robin850]

@bdolman : Awesome! Thanks a lot!

[robin850]

Finally, merge this. Thanks everyone! 🤘 ❤️