Crate wordvec

A thin and small vector that can fit data into a single usize.

See the readme on GitHub for detailed explanation of the memory layout.

When to use

Although the technical limit is N <= 127, it is not meaningful to set N such that align_of::<T>() + N * size_of::<T>() exceeds 24; WordVec has no advantage over SmallVec if it cannot pack into a smaller struct.

Thin vectors are significantly (several times) slower than conventional vectors since reading the length and capacity usually involves accessing memory out of active cache. Thus, heap layout is supposed to be the cold path. In other words, WordVec is basically “length should never exceed N, but behavior is still correct when it exceeds”.

Since the length encoding in the inlined layout is indirect (involves a bitshift), raw inlined access also tends to be slower in WordVec compared to SmallVec, as a tradeoff of reduced memory footprint of each vector alone. This may get handy in scenarios with a large array of small vectors, e.g. as an ECS component.

Structs

IntoIter

Implements IntoIterator for WordVec.

WordVec

A thin and small vector that can fit data into a single usize.