| hashbrown |
| ========= |
| |
| [](https://github.com/rust-lang/hashbrown/actions) |
| [](https://crates.io/crates/hashbrown) |
| [](https://docs.rs/hashbrown) |
| [](https://github.com/rust-lang/hashbrown) |
| |
| This crate is a Rust port of Google's high-performance [SwissTable] hash |
| map, adapted to make it a drop-in replacement for Rust's standard `HashMap` |
| and `HashSet` types. |
| |
| The original C++ version of SwissTable can be found [here], and this |
| [CppCon talk] gives an overview of how the algorithm works. |
| |
| Since Rust 1.36, this is now the `HashMap` implementation for the Rust standard |
| library. However you may still want to use this crate instead since it works |
| in environments without `std`, such as embedded systems and kernels. |
| |
| [SwissTable]: https://abseil.io/blog/20180927-swisstables |
| [here]: https://github.com/abseil/abseil-cpp/blob/master/absl/container/internal/raw_hash_set.h |
| [CppCon talk]: https://www.youtube.com/watch?v=ncHmEUmJZf4 |
| |
| ## [Change log](CHANGELOG.md) |
| |
| ## Features |
| |
| - Drop-in replacement for the standard library `HashMap` and `HashSet` types. |
| - Uses [foldhash](https://github.com/orlp/foldhash) as the default hasher, which is much faster than SipHash. |
| 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. |
| - Around 2x faster than the previous standard library `HashMap`. |
| - Lower memory usage: only 1 byte of overhead per entry instead of 8. |
| - Compatible with `#[no_std]` (but requires a global allocator with the `alloc` crate). |
| - Empty hash maps do not allocate any memory. |
| - SIMD lookups to scan multiple hash entries in parallel. |
| |
| ## Usage |
| |
| Add this to your `Cargo.toml`: |
| |
| ```toml |
| [dependencies] |
| hashbrown = "0.15" |
| ``` |
| |
| Then: |
| |
| ```rust |
| use hashbrown::HashMap; |
| |
| let mut map = HashMap::new(); |
| map.insert(1, "one"); |
| ``` |
| ## Flags |
| This crate has the following Cargo features: |
| |
| - `nightly`: Enables nightly-only features including: `#[may_dangle]`. |
| - `serde`: Enables serde serialization support. |
| - `rayon`: Enables rayon parallel iterator support. |
| - `equivalent`: Allows comparisons to be customized with the `Equivalent` trait. (enabled by default) |
| - `raw-entry`: Enables access to the deprecated `RawEntry` API. |
| - `inline-more`: Adds inline hints to most functions, improving run-time performance at the cost |
| of compilation time. (enabled by default) |
| - `default-hasher`: Compiles with foldhash as default hasher. (enabled by default) |
| - `allocator-api2`: Enables support for allocators that support `allocator-api2`. (enabled by default) |
| |
| ## License |
| |
| Licensed under either of: |
| |
| * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or https://www.apache.org/licenses/LICENSE-2.0) |
| * MIT license ([LICENSE-MIT](LICENSE-MIT) or https://opensource.org/licenses/MIT) |
| |
| 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. |
