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use core::pin::Pin;
use pin_project_lite::pin_project;
pin_project! {
/// UnfoldState used for stream and sink unfolds
#[project = UnfoldStateProj]
#[project_replace = UnfoldStateProjReplace]
#[derive(Debug)]
pub(crate) enum UnfoldState<T, R> {
Value {
value: T,
},
Future {
#[pin]
future: R,
},
Empty,
}
}
impl<T, R> UnfoldState<T, R> {
pub(crate) fn project_future(self: Pin<&mut Self>) -> Option<Pin<&mut R>> {
match self.project() {
UnfoldStateProj::Future { future } => Some(future),
_ => None,
}
}
pub(crate) fn take_value(self: Pin<&mut Self>) -> Option<T> {
match &*self {
UnfoldState::Value { .. } => match self.project_replace(UnfoldState::Empty) {
UnfoldStateProjReplace::Value { value } => Some(value),
_ => unreachable!(),
},
_ => None,
}
}
}