Struct fn_cache::HashCache

pub struct HashCache<'a, I, O, V = O> where
    I: Eq + Hash,  { /* fields omitted */ }

A cache for a function which uses a HashMap.

The cache takes ownership of all inputs, but only passes a reference to the function, allowing it to store the input in the cache without any copies or clones.

The value in the cache V can be different than the output of the function O, as long as O implements Into<V>. If no conversion is required, than the V parameter can be elided.

The requirements for a HashMap must be met, specifically the keys must implement Eq and Hash, and the following propery must hold:

k1 == k2 -> hash(k1) == hash(k2)

Methods

impl<'a, I, O, V> HashCache<'a, I, O, V> where
    I: Eq + Hash,
    O: Into<V>, 

pub fn new<F>(f: F) -> Self where
    F: Fn(&mut Self, &I) -> O + 'a, 

Create a cache for the provided function. If the function stores references, the cache can only live as long as those references.

pub fn get(&mut self, input: I) -> &V

Retrieve a value stored in the cache. If the value does not yet exist in the cache, the function is called, and the result is added to the cache before returning it.