smol_str 0.1.9

small-string optimized string type with O(1) clone

smol_str

Build Status Crates.io API reference

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.