cached

simple rust caching macro

Easy to use function caching/memoization inspired by python decorators.

Function results are cached using the function's arguments as a key. All function arguments must implement Hash + Eq in order to cache. When a cached! defined function is called, the function's cache is first checked for an already computed (and still valid) value before evaluating the function body. cached! functions should not be used to produce side-effectual results!

Documentation

See examples for example of implementing a custom cache-store.

Usage

#[macro_use] extern crate cached;
// `cached!` macro requires the `lazy_static!` macro
#[macro_use] extern crate lazy_static;

use std::time::{Instant, Duration};
use std::thread::sleep;

use cached::SizedCache;


cached!{ SLOW: SizedCache = SizedCache::with_capacity(50); >>
fn slow(n: u32) -> () = {
    if n == 0 { return; }
    sleep(Duration::new(1, 0));
    slow(n-1)
}}

pub fn main() {
    println!("running fresh...");
    let now = Instant::now();
    slow(10);
    println!("fresh! elapsed: {}", now.elapsed().as_secs());

    println!("running cached...");
    let now = Instant::now();
    slow(10);
    println!("cached!! elapsed: {}", now.elapsed().as_secs());

    {
        use cached::Cached;  // must be in scope to access cache

        println!(" ** Cache info **");
        let cache = SLOW.lock().unwrap();
        println!("hits=1 -> {:?}", cache.cache_hits().unwrap() == 1);
        println!("misses=11 -> {:?}", cache.cache_misses().unwrap() == 11);
        // make sure the cache-lock is dropped
    }
}