caches 0.3.0

This is a Rust implementation for popular caches (support no_std).
Documentation 
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use caches::{OnEvictCallback, PutResult, RawLRU};
use std::sync::atomic::{AtomicU64, Ordering};
use std::sync::Arc;

// EvictedCounter is a callback which is used to record the number of evicted entries.
struct EvictedCounter {
    ctr: Arc<AtomicU64>,
}

impl EvictedCounter {
    pub fn new(ctr: Arc<AtomicU64>) -> Self {
        Self { ctr }
    }
}

impl OnEvictCallback for EvictedCounter {
    fn on_evict<K, V>(&self, _: &K, _: &V) {
        self.ctr.fetch_add(1, Ordering::SeqCst);
    }
}

fn main() {
    use caches::Cache;
    let counter = Arc::new(AtomicU64::new(0));

    let mut cache: RawLRU<u64, u64, EvictedCounter> =
        RawLRU::with_on_evict_cb(2, EvictedCounter::new(counter.clone())).unwrap();

    // fill the cache
    assert_eq!(cache.put(1, 1), PutResult::Put);
    assert_eq!(cache.put(2, 2), PutResult::Put);

    // put 3, should evict the entry (1, 1)
    assert_eq!(cache.put(3, 3), PutResult::Evicted { key: 1, value: 1 });

    // put 4, should evict the entry (2, 2)
    assert_eq!(cache.put(4, 4), PutResult::Evicted { key: 2, value: 2 });

    // get 3, should update the recent-ness
    assert_eq!(cache.get(&3), Some(&3));

    // put 5, should evict the entry (4, 4)
    assert_eq!(cache.put(5, 5), PutResult::Evicted { key: 4, value: 4 });

    assert_eq!(counter.load(Ordering::SeqCst), 3);
}