jamespfennell / smol_str

smol_str

A SmolStr is a string type that has the following properties:

• size_of::<SmolStr>() == size_of::<String>()
• Clone is O(1)
• Strings are stack-allocated if they are:
  • Up to 22 bytes long
  • Longer than 22 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

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.

Cargo features

• std (on by default): use the Rust standard library. Disable for no_std mode.

• derive: implement Serde traits for SmolStr.

• nosync: use Rc internally instead of Arc. This makes the SmolStr type more performant in single-threaded contexts, but it will not be Send or Sync.

MSRV Policy

Minimal Supported Rust Version: latest stable.

Bumping MSRV is not considered a semver-breaking change.