umbra_slice

umbra_slice provides a generic slice type that can replace Box<[T]> and Box<str>. UmbraSlice<T> is optimized to store small slices inline in a layout based on "German strings".

umbra_slice was extracted from spellbook. See the post "German string" optimizations in Spellbook for more details.

Quick facts

• Takes 16 bytes on the stack.
• Stores up to 14 bytes inline.
• Optimization for Eq to disqualify strings with different lengths and prefixes quickly.
• Can be used to store 16 or 32 bit integers as well as u8s.

(Assuming a 64-bit machine.)

Use-cases

UmbraSlice<T> and UmbraString are designed for a specific use-case and should not be thought of as generic replacements for Vec<T>/Box<[T]> and String/Box<str>, respectively. If you need a generic replacement, consider one of many great existing crates like smallvec. UmbraSlice<T> differs from most existing crates because it focuses on emulating non-resizable, immutable slices rather than resizable and mutable Vec<T>s (which typically take 24 bytes on the stack).

Umbra slices are immutable and have a shorter maximum length than Vecs or boxed slices. Umbra slices are meant to be used when you have very many (thousands+) slices or strings which are typically smaller than 14 bytes.

License

Licensed under either of:

• MPL version 2.0 (LICENSE-MPL or https://www.mozilla.org/en-US/MPL/2.0/)
• Apache License, Version 2.0, (LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0)

at your option.