1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
|
//! A mapper based on a function from keys to values.
use std::pin::Pin;
use crate::lazy_mapping::{LazyMapper, LazyMappingBackend};
/// A function from keys to values.
///
/// Should be pure, except for use of other mappings. This ensures recomputation is done when needed.
pub trait Thunk<K, V>: Send + 'static {
fn compute(&self, key: K) -> Pin<Box<dyn std::future::Future<Output = V> + Send + '_>>;
}
#[derive(Debug, Default)]
pub struct ThunkBackend<T> {
thunk: T,
}
impl<T> ThunkBackend<T> {
pub fn new(thunk: T) -> Self {
Self { thunk }
}
pub fn thunk(&self) -> &T {
&self.thunk
}
}
impl<K, V: 'static, T> LazyMappingBackend<K, V> for ThunkBackend<T>
where
T: Thunk<K, V>,
{
async fn is_dirty(&self, _: &K) -> bool {
false // only dirty if marked dirty by someting else
}
fn compute(&self, key: K) -> impl std::future::Future<Output = V> + Send + '_ {
self.thunk.compute(key)
}
}
pub type ThunkMapper<K, V, T> = LazyMapper<K, V, ThunkBackend<T>>;
|
