sodium_rust/impl_/
lazy.rs

1use parking_lot::Mutex;
2use std::sync::Arc;
3
4/// A representation for a value that may not be available until the
5/// current transaction is closed.
6pub struct Lazy<A> {
7    data: Arc<Mutex<LazyData<A>>>,
8}
9
10impl<A> Clone for Lazy<A> {
11    fn clone(&self) -> Self {
12        Lazy {
13            data: self.data.clone(),
14        }
15    }
16}
17
18pub enum LazyData<A> {
19    Thunk(Box<dyn FnMut() -> A + Send>),
20    Value(A),
21}
22
23impl<A: Send + Clone + 'static> Lazy<A> {
24    /// Create a new `Lazy` whose value will be computed with the
25    /// given function sometime after the end of the current
26    /// transaction.
27    pub fn new<THUNK: FnMut() -> A + Send + 'static>(thunk: THUNK) -> Lazy<A> {
28        Lazy {
29            data: Arc::new(Mutex::new(LazyData::Thunk(Box::new(thunk)))),
30        }
31    }
32
33    /// Create a new immediately ready `Lazy` value from the given value.
34    pub fn of_value(value: A) -> Lazy<A> {
35        Lazy {
36            data: Arc::new(Mutex::new(LazyData::Value(value))),
37        }
38    }
39
40    /// Retrieve the value of this `Lazy` either by running the
41    /// supplied function or returning the already computed value.
42    pub fn run(&self) -> A {
43        let mut data = self.data.lock();
44        let next_op: Option<LazyData<A>>;
45        let result: A;
46        match &mut *data {
47            LazyData::Thunk(ref mut k) => {
48                result = k();
49                next_op = Some(LazyData::Value(result.clone()));
50            }
51            LazyData::Value(ref x) => {
52                result = x.clone();
53                next_op = None;
54            }
55        }
56        if let Some(next) = next_op {
57            *data = next;
58        }
59        result
60    }
61}
sodium_rust/impl_/lazy.rs

sodium_rust/impl_/
lazy.rs
