kitchen_sink.rs

#[macro_use]
extern crate cached;

use std::cmp::Eq;
use std::collections::{hash_map::Entry, HashMap};
use std::hash::Hash;

use std::thread::sleep;
use std::time::Duration;

use cached::{Cached, SizedCache, UnboundCache};

// cached shorthand, uses the default unbounded cache.
// Equivalent to specifying `FIB: UnboundCache<(u32), u32> = UnboundCache::new();`
cached! {
    FIB;
    fn fib(n: u32) -> u32 = {
        if n == 0 || n == 1 { return n; }
        fib(n-1) + fib(n-2)
    }
}

// Same as above, but preallocates some space.
// Note that the cache key type is a tuple of function argument types.
cached! {
    FIB_SPECIFIC: UnboundCache<u32, u32> = UnboundCache::with_capacity(50);
    fn fib_specific(n: u32) -> u32 = {
        if n == 0 || n == 1 { return n; }
        fib_specific(n-1) + fib_specific(n-2)
    }
}

// Specify a specific cache type
// Note that the cache key type is a tuple of function argument types.
cached! {
    SLOW: SizedCache<(u32, u32), u32> = SizedCache::with_size(100);
    fn slow(a: u32, b: u32) -> u32 = {
        sleep(Duration::new(2, 0));
        a * b
    }
}

// Specify a specific cache type and an explicit key expression
// Note that the cache key type is a `String` created from the borrow arguments
cached_key! {
    KEYED: SizedCache<String, usize> = SizedCache::with_size(100);
    Key = { format!("{a}{b}") };
    fn keyed(a: &str, b: &str) -> usize = {
        let size = a.len() + b.len();
        sleep(Duration::new(size as u64, 0));
        size
    }
}

// Implement our own cache type
struct MyCache<K: Hash + Eq, V> {
    store: HashMap<K, V>,
    capacity: usize,
}
impl<K: Hash + Eq, V> MyCache<K, V> {
    pub fn with_capacity(size: usize) -> MyCache<K, V> {
        MyCache {
            store: HashMap::with_capacity(size),
            capacity: size,
        }
    }
}
impl<K: Hash + Eq, V> Cached<K, V> for MyCache<K, V> {
    fn cache_get<Q>(&mut self, k: &Q) -> Option<&V>
    where
        K: std::borrow::Borrow<Q>,
        Q: std::hash::Hash + Eq + ?Sized,
    {
        self.store.get(k)
    }
    fn cache_get_mut<Q>(&mut self, k: &Q) -> Option<&mut V>
    where
        K: std::borrow::Borrow<Q>,
        Q: std::hash::Hash + Eq + ?Sized,
    {
        self.store.get_mut(k)
    }
    fn cache_get_or_set_with<F: FnOnce() -> V>(&mut self, k: K, f: F) -> &mut V {
        self.store.entry(k).or_insert_with(f)
    }
    fn cache_try_get_or_set_with<F: FnOnce() -> Result<V, E>, E>(
        &mut self,
        k: K,
        f: F,
    ) -> Result<&mut V, E> {
        let v = match self.store.entry(k) {
            Entry::Occupied(occupied) => occupied.into_mut(),
            Entry::Vacant(vacant) => vacant.insert(f()?),
        };

        Ok(v)
    }
    fn cache_set(&mut self, k: K, v: V) -> Option<V> {
        self.store.insert(k, v)
    }
    fn cache_remove<Q>(&mut self, k: &Q) -> Option<V>
    where
        K: std::borrow::Borrow<Q>,
        Q: std::hash::Hash + Eq + ?Sized,
    {
        self.store.remove(k)
    }
    fn cache_clear(&mut self) {
        self.store.clear();
    }
    fn cache_reset(&mut self) {
        self.store = HashMap::with_capacity(self.capacity);
    }
    fn cache_size(&self) -> usize {
        self.store.len()
    }
}

// Specify our custom cache and supply an instance to use
cached! {
    CUSTOM: MyCache<u32, ()> = MyCache::with_capacity(50);
    fn custom(n: u32) -> () = {
        if n == 0 { return; }
        custom(n-1);
    }
}

pub fn main() {
    println!("\n ** default cache **");
    fib(3);
    fib(3);
    {
        let cache = FIB.lock().unwrap();
        println!("hits: {:?}", cache.cache_hits());
        println!("misses: {:?}", cache.cache_misses());
        // make sure lock is dropped
    }
    fib(10);
    fib(10);

    println!("\n ** specific cache **");
    fib_specific(20);
    fib_specific(20);
    {
        let cache = FIB_SPECIFIC.lock().unwrap();
        println!("hits: {:?}", cache.cache_hits());
        println!("misses: {:?}", cache.cache_misses());
        // make sure lock is dropped
    }
    fib_specific(20);
    fib_specific(20);

    println!("\n ** custom cache **");
    custom(25);
    {
        let cache = CUSTOM.lock().unwrap();
        println!("hits: {:?}", cache.cache_hits());
        println!("misses: {:?}", cache.cache_misses());
        // make sure lock is dropped
    }

    println!("\n ** slow func **");
    println!(" - first run `slow(10)`");
    slow(10, 10);
    println!(" - second run `slow(10)`");
    slow(10, 10);
    {
        let cache = SLOW.lock().unwrap();
        println!("hits: {:?}", cache.cache_hits());
        println!("misses: {:?}", cache.cache_misses());
        // make sure the cache-lock is dropped
    }

    println!("done!");
}