[tudorb]

I'm Tudor, one of the main folly authors. I wrote format, Arena / ThreadCachedArena, DiscriminatedPtr, GroupVarint, TimeoutQueue, and various other pieces (parts of String.h, ThreadLocal, etc), and I'm pretty well-versed with the entire library so I can reasonably answer questions (or poke the appropriate people to make a HN account and answer). Ask away.

[chrisaycock]

Not necessarily specific to Folly, but I've wondered why vector classes don't have a "short vector optimization" like string classes do. That is, why don't they store 24 bytes or so in place? Is it because the required iterators would take-up too much space anyway?

[tudorb]

folly::small_vector does just that (and it lets you use one bit for a mutex, too! -- we have a lot of memory-constrained apps so we had to design data structures for them).

We might unify that with fbvector eventually.