# LRU Cache

[![Travis Badge]][build status]
[![Codecov Badge]][coverage status]
[![crates.io Badge]][crates.io package]
[![docs.rs Badge]][docs.rs documentation]
[![License Badge]][license]

[Documentation]

An implementation of a LRU cache. The cache supports `put`, `get`, `get_mut` and `pop` operations,
all of which are O(1). This crate was heavily influenced by the [LRU Cache implementation in an
earlier version of Rust's std::collections crate].

The MSRV for this crate is 1.56.0.

## Example

Below is a simple example of how to instantiate and use a LRU cache.

```rust,no_run
extern crate lru;

use lru::LruCache;
use std::num::NonZeroUsize;

fn main() {
    let mut cache = LruCache::new(NonZeroUsize::new(2).unwrap());
    cache.put("apple", 3);
    cache.put("banana", 2);

    assert_eq!(*cache.get(&"apple").unwrap(), 3);
    assert_eq!(*cache.get(&"banana").unwrap(), 2);
    assert!(cache.get(&"pear").is_none());

    assert_eq!(cache.put("banana", 4), Some(2));
    assert_eq!(cache.put("pear", 5), None);

    assert_eq!(*cache.get(&"pear").unwrap(), 5);
    assert_eq!(*cache.get(&"banana").unwrap(), 4);
    assert!(cache.get(&"apple").is_none());

    {
        let v = cache.get_mut(&"banana").unwrap();
        *v = 6;
    }

    assert_eq!(*cache.get(&"banana").unwrap(), 6);
}
```

[travis badge]: https://travis-ci.org/jeromefroe/lru-rs.svg?branch=master
[build status]: https://travis-ci.org/jeromefroe/lru-rs
[codecov badge]: https://codecov.io/gh/jeromefroe/lru-rs/branch/master/graph/badge.svg
[coverage status]: https://codecov.io/gh/jeromefroe/lru-rs
[crates.io badge]: https://img.shields.io/crates/v/lru.svg
[crates.io package]: https://crates.io/crates/lru/
[documentation]: https://docs.rs/lru/
[docs.rs badge]: https://docs.rs/lru/badge.svg
[docs.rs documentation]: https://docs.rs/lru/
[license badge]: https://img.shields.io/badge/license-MIT-blue.svg
[license]: https://raw.githubusercontent.com/jeromefroe/lru-rs/master/LICENSE
[lru cache implementation in an earlier version of rust's std::collections crate]: https://doc.rust-lang.org/0.12.0/std/collections/lru_cache/struct.LruCache.html