Verifying if character is corrupted, meaning that one more char is needed.

[josedonizetti]

@headius and @enebo this patch fixes the problem we discussed on irc today, specs for readlines and foreach pass, and the File.new('a.txt').gets(5) that Charles did also works.
I came to that comparison "<-1" after debugging the MRI code and seeing that it is exactly what they do there. What do you think about it?

[enebo]

I have not really dug into MRI to verify this is correct but the <-1 comparison seems like it is difficult for a new reader (or me) to understand what that conditional represents. Do they perhaps have this in some encoding or oniguruma method which hides the -1 part and possibly gives a name which represents this better? If we do roll with this exact patch we minimally have to add a comment explaining the why of the -1 check.

[josedonizetti]

Yup, they hide it on the onigurama, but the name they use is also not understandable for me https://github.com/ruby/ruby/blob/trunk/include/ruby/oniguruma.h#L253, the call that relax the limit to get one more bite on foreach/readlines is https://github.com/ruby/ruby/blob/trunk/io.c#L3058, I can use the same name they are using with a private method and comment the goal of doing it.

[enebo]

Could you just add that as a sensibly-named method (isIncompleteChar maybe?) in StringSupport.java and the put a comment above that method mentioning MRI name (e.g. // mri: ONIGENC_MBCLEN_NEEDMORE_P)? I am cool with landing this after seeing that code, but the explicit -1 check will end up being confusing...I am betting this is not the only place that macro is used either so we might as well put it in a method.

[josedonizetti]

Done. Thanks for the tips.

[headius]

Thanks for the extra legwork on this one!