Using a slab

Some algorithms require you to hold access tokens to data that may or may not exist. This could be solved in Rust by using  Vec<Option<T>>, and treating the index of your data as a token. But we can do better! slab is an optimized abstraction of exactly this concept.

While it is not meant as a general-purpose collection, slab can help you a lot if you use it in the right places.

How to do it...

1. Open the Cargo.toml file that has been generated earlier for you.

2. Under [dependencies], add the following line:

slab = "0.4.0"

3. If you want, you can go to slab's crates.io page (https://crates.io/crates/slab) to check for the newest version, and use that one instead.

4. In the folder bin, create a file called slab.rs.

5. Add the following code, and run it with cargo run --bin slab:

1   extern crate slab;
2   use slab::{Slab, VacantEntry};
3 
4   fn main() {
5     // A slab is meant to be used as a limited buffer
6     // As such, you should initialize it with a pre-
7     // defined capacity...