debris / elastic-array Goto Github PK

It would be desirable to be able to use elastic-array in a no_std context. The main thing blocking this is the heapsize dependency. Maybe it can be made optional?

Used here.

Using uninitialized, you run into the same soundness issues already explored by crates arrayvec and smallvec.

See bugs servo/rust-smallvec/issues/4 and servo/rust-smallvec/issues/5

Not sure why we have a fork there, but maybe we should close this one and move activity over there?

This PR renaming to_vec to into_vec accidentally introduced a silent performance regression between 0.8 and 0.9. Since ElasticArray implements Deref<Target=[u8]>, all the usages of ElasticArray::to_vec in the code have now silently been replaced with <&[T]>::to_vec, which is consistently O(n) (whereas ElasticArray::to_vec is either O(1) or O(n) depending on the size of the array). I discovered this when I migrated to 0.9 and the compilation still succeeded. I don't know there's much we can do about this other than documenting it, but it is something that I'd say needs to be documented.

It should be noted that this doesn't actually affect the Parity codebase, since I just ran it through sed and then fixed the places where it really did need to be to_vec. Maybe it would be worth pinging our reverse dependencies.

AFAICT, it is not possible (or rather, easy) to have a std::borrow::Cow where the Owned is an ElasticArray. In order for this to be possible, we need a new type representing a reference to an ElasticArray contents that implements ToOwned<Owned=ElasticArray...>. Any thoughts on creating such a type? I'm not sure exactly what to call it. Maybe like ElasticArrayRefN?