futures_util/
unfold_state.rs

1use core::pin::Pin;
2
3use pin_project_lite::pin_project;
4
5pin_project! {
6    /// UnfoldState used for stream and sink unfolds
7    #[project = UnfoldStateProj]
8    #[project_replace = UnfoldStateProjReplace]
9    #[derive(Debug)]
10    pub(crate) enum UnfoldState<T, R> {
11        Value {
12            value: T,
13        },
14        Future {
15            #[pin]
16            future: R,
17        },
18        Empty,
19    }
20}
21
22impl<T, R> UnfoldState<T, R> {
23    pub(crate) fn project_future(self: Pin<&mut Self>) -> Option<Pin<&mut R>> {
24        match self.project() {
25            UnfoldStateProj::Future { future } => Some(future),
26            _ => None,
27        }
28    }
29
30    pub(crate) fn take_value(self: Pin<&mut Self>) -> Option<T> {
31        match &*self {
32            Self::Value { .. } => match self.project_replace(Self::Empty) {
33                UnfoldStateProjReplace::Value { value } => Some(value),
34                _ => unreachable!(),
35            },
36            _ => None,
37        }
38    }
39}
futures_util/unfold_state.rs

futures_util/
unfold_state.rs
