Crate weight_cache[−][src]
A cache that holds a limited number of key-value pairs. When the capacity of the cache is exceeded, the least-recently-used (where “used” means a look-up or putting the pair into the cache) pair is automatically removed.
Contrary to the lru-cache crate (which
this crate is heavily inspired by!), the capacity is not the number of items
in the cache, but can be given by an arbitrary criterion by implementing
Weigheable
for the value type V. A straight-forward example of this would
be to use the allocated size of the object, and provide a total capacity
which must not be exceeded by the cache.
Examples
use weight_cache::{Weigheable, WeightCache}; use std::num::NonZeroUsize; #[derive(PartialEq, Debug)] enum Food { Milk { milliliters: usize }, Cucumber { pieces: usize }, Meat { grams: usize }, Potato { pieces: usize }, Crab { grams: usize }, } impl Weigheable for Food { fn measure(value: &Self) -> usize { match value { Food::Milk { milliliters } => milliliters * 104 / 100, Food::Cucumber { pieces } => pieces * 158, Food::Meat { grams } => *grams, Food::Potato { pieces } => pieces * 175, Food::Crab { grams } => *grams, } } } let mut cache = WeightCache::new(NonZeroUsize::new(500).unwrap()); // Can't put too much in! assert!(cache.put(0, Food::Meat { grams: 600 }).is_err()); assert!(cache.is_empty()); cache.put(1, Food::Milk { milliliters: 100 }).unwrap(); assert!(!cache.is_empty()); assert_eq!(*cache.get_mut(&1).unwrap(), Food::Milk { milliliters: 100 }); cache.put(2, Food::Crab { grams: 300 }).unwrap(); assert_eq!(*cache.get_mut(&2).unwrap(), Food::Crab { grams: 300 }); assert_eq!(*cache.get_mut(&1).unwrap(), Food::Milk { milliliters: 100 }); cache.put(3, Food::Potato { pieces: 2 }).unwrap(); assert_eq!(*cache.get_mut(&3).unwrap(), Food::Potato { pieces: 2}); assert!(cache.get_mut(&2).is_none()); // 1 has been touched last assert_eq!(*cache.get_mut(&1).unwrap(), Food::Milk { milliliters: 100 });
Structs
IntoIter | An iterator over a cache’s key-value pairs in least- to most-recently-used order. |
Iter | An iterator over a cache’s key-value pairs in least- to most-recently-used order. |
IterMut | An iterator over a cache’s key-value pairs in least- to most-recently-used order with mutable references to the values. |
ValueTooBigError | An error indicating that the to-be-inserted value is bigger than the max size of the cache. |
WeightCache |
Traits
Weigheable | A trait to implemented for the value type, providing a way to
|