1hashbrown 2========= 3 4[](https://github.com/rust-lang/hashbrown/actions) 5[](https://crates.io/crates/hashbrown) 6[](https://docs.rs/hashbrown) 7[](https://github.com/rust-lang/hashbrown) 8 9This crate is a Rust port of Google's high-performance [SwissTable] hash 10map, adapted to make it a drop-in replacement for Rust's standard `HashMap` 11and `HashSet` types. 12 13The original C++ version of SwissTable can be found [here], and this 14[CppCon talk] gives an overview of how the algorithm works. 15 16Since Rust 1.36, this is now the `HashMap` implementation for the Rust standard 17library. However you may still want to use this crate instead since it works 18in environments without `std`, such as embedded systems and kernels. 19 20[SwissTable]: https://abseil.io/blog/20180927-swisstables 21[here]: https://github.com/abseil/abseil-cpp/blob/master/absl/container/internal/raw_hash_set.h 22[CppCon talk]: https://www.youtube.com/watch?v=ncHmEUmJZf4 23 24## [Change log](CHANGELOG.md) 25 26## Features 27 28- Drop-in replacement for the standard library `HashMap` and `HashSet` types. 29- Uses [foldhash](https://github.com/orlp/foldhash) as the default hasher, which is much faster than SipHash. 30 However, foldhash does *not provide the same level of HashDoS resistance* as SipHash, so if that is important to you, you might want to consider using a different hasher. 31- Around 2x faster than the previous standard library `HashMap`. 32- Lower memory usage: only 1 byte of overhead per entry instead of 8. 33- Compatible with `#[no_std]` (but requires a global allocator with the `alloc` crate). 34- Empty hash maps do not allocate any memory. 35- SIMD lookups to scan multiple hash entries in parallel. 36 37## Usage 38 39Add this to your `Cargo.toml`: 40 41```toml 42[dependencies] 43hashbrown = "0.14" 44``` 45 46Then: 47 48```rust 49use hashbrown::HashMap; 50 51let mut map = HashMap::new(); 52map.insert(1, "one"); 53``` 54## Flags 55This crate has the following Cargo features: 56 57- `nightly`: Enables nightly-only features including: `#[may_dangle]`. 58- `serde`: Enables serde serialization support. 59- `borsh`: Enables borsh serialization support. 60- `rayon`: Enables rayon parallel iterator support. 61- `equivalent`: Allows comparisons to be customized with the `Equivalent` trait. (enabled by default) 62- `raw-entry`: Enables access to the deprecated `RawEntry` API. 63- `inline-more`: Adds inline hints to most functions, improving run-time performance at the cost 64 of compilation time. (enabled by default) 65- `default-hasher`: Compiles with foldhash as default hasher. (enabled by default) 66- `allocator-api2`: Enables support for allocators that support `allocator-api2`. (enabled by default) 67 68## License 69 70Licensed under either of: 71 72 * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or https://www.apache.org/licenses/LICENSE-2.0) 73 * MIT license ([LICENSE-MIT](LICENSE-MIT) or https://opensource.org/licenses/MIT) 74 75at your option. 76 77### Contribution 78 79Unless you explicitly state otherwise, any contribution intentionally submitted 80for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any 81additional terms or conditions. 82
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