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
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
use crate::{
cps::{self, AsyncStack, ContinuationFunction, StepFunction},
Arc, Closure,
};
use core::{intrinsics::transmute, task::Poll};
use futures::future::poll_fn;
type InitialStepFunction<T, V> = extern "C" fn(
stack: &mut AsyncStack<T>,
continuation: ContinuationFunction<T, T>,
closure: Arc<Closure<V>>,
) -> cps::Result;
const INITIAL_STACK_CAPACITY: usize = 64;
pub async fn from_closure<T, V>(closure: Arc<Closure<T>>) -> V {
let mut trampoline: Option<(StepFunction<(), V>, ContinuationFunction<(), V>)> = None;
let mut stack = AsyncStack::new(INITIAL_STACK_CAPACITY);
poll_fn(move |context| {
stack.run_with_context(context, |stack| {
if let Some((step, continue_)) = trampoline {
step(stack, continue_);
} else {
unsafe {
let entry_function =
transmute::<_, InitialStepFunction<V, T>>(closure.entry_function());
entry_function(stack, resolve, closure.clone());
}
}
});
if let Some(value) = stack.resolved_value() {
value.into()
} else {
trampoline = Some(stack.resume().unwrap());
Poll::Pending
}
})
.await
}
extern "C" fn resolve<T>(stack: &mut AsyncStack<T>, value: T) -> cps::Result {
stack.resolve(value);
cps::Result::new()
}
#[cfg(test)]
mod tests {
use super::*;
use crate::Number;
extern "C" fn foo(
stack: &mut AsyncStack,
continue_: ContinuationFunction<Number>,
closure: Arc<Closure<f64>>,
) -> cps::Result {
unsafe { continue_(stack, (*closure.payload()).into()) }
}
#[tokio::test]
async fn convert_closure() {
let value = 42.0;
assert_eq!(
from_closure::<_, Number>(Arc::new(Closure::new(foo as *const u8, value))).await,
value.into()
);
}
}