A SmolStr is a string type that has the following properties:
size_of::<SmolStr>() == 24 (therefore == size_of::<String>() on 64 bit platforms)Clone is O(1) (no allocation)- Strings are stack-allocated if they are:
- Up to 23 bytes long
- Longer than 23 bytes, but substrings of
WS (see src/lib.rs). Such strings consist
solely of consecutive newlines, followed by consecutive spaces
- If a string does not satisfy the aforementioned conditions, it is heap-allocated
- Additionally, a
SmolStr can be explicitly created from a &'static str without allocation
Unlike String, however, SmolStr is immutable. The primary use case for
SmolStr is a good enough default storage for tokens of typical programming
languages. Strings consisting of a series of newlines, followed by a series of
whitespace are a typical pattern in computer programs because of indentation.
Note that a specialized interner might be a better solution for some use cases.
Run criterion benches with
cargo bench --bench \* -- --quick
Minimal Supported Rust Version: latest stable.
Bumping MSRV is not considered a semver-breaking change.