[](https://github.com/yegor256/micromap/actions/workflows/cargo.yml)
[](https://crates.io/crates/micromap)
[](https://codecov.io/gh/yegor256/micromap)
[](https://hitsofcode.com/view/github/yegor256/micromap)
[](https://github.com/yegor256/micromap/blob/master/LICENSE.txt)
[](https://docs.rs/micromap/latest/micromap/)
At least **5x faster** alternative of [`HashMap`](https://doc.rust-lang.org/std/collections/struct.HashMap.html),
for very small maps. It is also faster than
[FxHashMap](https://github.com/rust-lang/rustc-hash),
[ArrayMap](https://github.com/robjtede/tinymap). The smaller the map, the higher the
performance. When the map is larger than 50, it is better to use standard
[`HashMap`](https://doc.rust-lang.org/std/collections/struct.HashMap.html), since
the performance of `micromap::Map` _may_ start to degrade.
The only important restriction is that both key and value must implement the `Copy` trait.
**WELCOME**:
Not all functions that a user expects to have in a map are implemented.
I will appreciate if you contribute by implementing these missing functions.
Here is how you use it:
```rust
use micromap::Map;
let mut m : Map<u64, &str, 10> = Map::new();
m.insert(1, "foo");
m.insert(2, "bar");
assert_eq!(2, m.len());
```
Pay attention, here the map is created with an extra generic argument `10`. This is
the total size of the map, which is allocated on stack when `::new()` is called.
Unlike `HashMap`, the `Map` doesn't use heap at all.
Read [the API documentation](https://docs.rs/micromap/latest/micromap/). The struct
[`micromap::Map`](https://docs.rs/micromap/latest/micromap/struct.Map.html) is designed as closely similar to
[`std::collections::HashMap`](https://doc.rust-lang.org/std/collections/struct.HashMap.html) as possible.
## How to Contribute
First, install [Rust](https://www.rust-lang.org/tools/install) and then:
```bash
$ cargo test -vv
```
If everything goes well, fork repository, make changes, send us a [pull request](https://www.yegor256.com/2014/04/15/github-guidelines.html).
We will review your changes and apply them to the `master` branch shortly,
provided they don't violate our quality standards. To avoid frustration,
before sending us your pull request please run `cargo test` again. Also,
run `cargo fmt` and `cargo clippy`.