Use iterative parse method instead of recursive parse

[calio]

The original recursive parse would cause stack size exceeding system limit and a segment fault when dealing with large date ( usually 100k lines or more ).

[agentzh]

I'll look into this. Thanks for the patch!

[msva]

@agentzh, ping?

[agentzh]

@msva I'll look into this at some point. Sorry for the delay.