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use std::{
future::Future,
marker::PhantomData,
pin::Pin,
task::{Context, Poll},
};
use super::raw::RawTask;
/// JoinHandle can be used to wait task finished.
/// Note if you drop it directly, task will not be terminated.
pub struct JoinHandle<T> {
raw: RawTask,
_p: PhantomData<T>,
}
unsafe impl<T: Send> Send for JoinHandle<T> {}
unsafe impl<T: Send> Sync for JoinHandle<T> {}
impl<T> JoinHandle<T> {
pub(super) fn new(raw: RawTask) -> JoinHandle<T> {
JoinHandle {
raw,
_p: PhantomData,
}
}
/// Checks if the task associated with this `JoinHandle` has finished.
pub fn is_finished(&self) -> bool {
let state = self.raw.header().state.load();
state.is_complete()
}
}
impl<T> Unpin for JoinHandle<T> {}
impl<T> Future for JoinHandle<T> {
type Output = T;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let mut ret = Poll::Pending;
// Try to read the task output. If the task is not yet complete, the
// waker is stored and is notified once the task does complete.
//
// The function must go via the vtable, which requires erasing generic
// types. To do this, the function "return" is placed on the stack
// **before** calling the function and is passed into the function using
// `*mut ()`.
//
// Safety:
//
// The type of `T` must match the task's output type.
unsafe {
self.raw
.try_read_output(&mut ret as *mut _ as *mut (), cx.waker());
}
ret
}
}
impl<T> Drop for JoinHandle<T> {
fn drop(&mut self) {
if self.raw.header().state.drop_join_handle_fast().is_ok() {
return;
}
self.raw.drop_join_handle_slow();
}
}
|
