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String optimized for map keys

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cobalt-org/kstring

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KString

Key String: Optimized for map keys.

Crates Status

Background

Considerations:

  • Large maps
  • Most keys live and drop without being used in any other way
  • Most keys are relatively small (single to double digit bytes)
  • Keys are immutable
  • Allow zero-cost abstractions between structs and maps (e.g. no allocating when dealing with struct field names)

Ramifications:

  • Inline small strings rather than going to the heap.
  • Preserve &'static str across strings (KString), references (KStringRef), and lifetime abstractions (KStringCow) to avoid allocating for struct field names.
  • Use Box<str> rather than String to use less memory.

Features

  • max_inline: Instead of aligning the inline-string for performance (15 bytes + length on 64-bit), use the full width (22 bytes on 64-bit)
  • arc: Instead of using Box<str>, use Arc<str>. Note: allocations are fast enough that this can actually slow things down for small enough strings.

Alternatives, see string-benchmarks-rs

License

Licensed under either of

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.