Note: this crate is still in heavy development. Please be careful!
This crate provides a map implementation that relies on fixed-size backing storage.
It accomplishes this by deriving an optimal storage strategy from the key to be used in the map
using the Key derive:
```rust
pub enum Part { First, Second, }
pub enum Key { Simple, Composite(Part), }
let mut map = fixedmap::Map::new(); asserteq!(map.get(Key::Simple), None);
map.insert(Key::Simple, 1); map.insert(Key::Composite(Part::One), 2);
asserteq!(map.get(Key::Simple), Some(&1)); asserteq!(map.get(Key::Composite(Part::One)), Some(&2)); assert_eq!(map.get(Key::Composite(Part::Two)), None); ```
The API of this project is incomplete since it is experimental. You can help by adding more!
There are many cases where you want associate a value with a small, fixed number of elements identified by an enum.
For example, let's say you have a game where each room has something in for directions:
```rust
pub enum Dir { North, East, South, West, } ```
Now we can use this map to associate an item with each direction.
rust
let mut map = fixed_map::Map::new();
map.insert(Dir::North, Item::Bow);
The goal is for the performance of fixed-map to be identical to storing the data linearly in memory.
In the following benchmarks, fixed-map is compared to:
hashbrown] - a high performance hash map.array, which is a simple [Option<Key>; 4] array.``` get/fixed_map time: [255.71 ps 257.67 ps 259.98 ps] get/array time: [512.06 ps 514.43 ps 516.83 ps] get/hashbrown time: [3.2981 ns 3.3287 ns 3.3607 ns]
insert/fixed_map time: [254.23 ps 255.44 ps 257.31 ps] insert/array time: [274.18 ps 275.29 ps 276.47 ps] insert/hashbrown time: [35.409 ns 35.635 ns 35.861 ns]
iter/fixed_map time: [249.76 ps 251.58 ps 253.69 ps] iter/array time: [256.04 ps 259.76 ps 264.41 ps] iter/hashbrown time: [1.5128 ns 1.5322 ns 1.5534 ns] ```
This project is distributed under the terms of both the MIT license and the Apache License (Version 2.0).
This project contains code derived from [HashMap] (Rust stdlib).