train_map/
lib.rs

1#![doc = include_str!("../README.md")]
2
3use std::{borrow::Borrow, collections::HashMap, hash::Hash};
4
5#[derive(Clone, Debug)]
6pub struct TrainMap<'a, K, V> {
7    map: HashMap<K, V>,
8    parent: Option<&'a TrainMap<'a, K, V>>,
9}
10
11impl<'a, K: Eq + Hash, V> TrainMap<'a, K, V> {
12    pub fn new() -> Self {
13        Self {
14            map: Default::default(),
15            parent: None,
16        }
17    }
18
19    pub fn with_capacity(capacity: usize) -> Self {
20        Self {
21            map: HashMap::with_capacity(capacity),
22            parent: None,
23        }
24    }
25
26    pub fn get<Q: Eq + Hash + ?Sized>(&self, key: &Q) -> Option<&V>
27    where
28        K: Borrow<Q>,
29    {
30        if let Some(value) = self.map.get(key) {
31            Some(value)
32        } else if let Some(parent) = self.parent {
33            parent.get(key)
34        } else {
35            None
36        }
37    }
38
39    pub fn insert(&mut self, key: K, value: V) -> Option<V> {
40        self.map.insert(key, value)
41    }
42
43    pub fn fork(&'a self) -> Self {
44        Self {
45            map: Default::default(),
46            parent: Some(self),
47        }
48    }
49}
50
51impl<'a, K: Eq + Hash, V> Default for TrainMap<'a, K, V> {
52    fn default() -> Self {
53        Self::new()
54    }
55}
56
57impl<'a, K: Eq + Hash, V> Extend<(K, V)> for TrainMap<'a, K, V> {
58    fn extend<T: IntoIterator<Item = (K, V)>>(&mut self, iterator: T) {
59        self.map.extend(iterator)
60    }
61}
train_map/lib.rs

train_map/
lib.rs
