refactor

veilid-tools/src/must_join_handle.rs

@@ -0,0 +1,90 @@
+use super::*;
+
+use core::task::{Context, Poll};
+
+#[derive(Debug)]
+pub struct MustJoinHandle<T> {
+    join_handle: Option<LowLevelJoinHandle<T>>,
+    completed: bool,
+}
+
+impl<T> MustJoinHandle<T> {
+    pub fn new(join_handle: LowLevelJoinHandle<T>) -> Self {
+        Self {
+            join_handle: Some(join_handle),
+            completed: false,
+        }
+    }
+
+    #[allow(unused_mut)]
+    pub async fn abort(mut self) {
+        if !self.completed {
+            cfg_if! {
+                if #[cfg(feature="rt-async-std")] {
+                    if let Some(jh) = self.join_handle.take() {
+                        jh.cancel().await;
+                        self.completed = true;
+                    }
+                } else if #[cfg(feature="rt-tokio")] {
+                    if let Some(jh) = self.join_handle.take() {
+                        jh.abort();
+                        let _ = jh.await;
+                        self.completed = true;
+                    }
+                } else if #[cfg(target_arch = "wasm32")] {
+                    drop(self.join_handle.take());
+                    self.completed = true;
+                } else {
+                    compile_error!("needs executor implementation")
+                }
+
+            }
+        }
+    }
+}
+
+impl<T> Drop for MustJoinHandle<T> {
+    fn drop(&mut self) {
+        // panic if we haven't completed
+        if !self.completed {
+            panic!("MustJoinHandle was not completed upon drop. Add cooperative cancellation where appropriate to ensure this is completed before drop.")
+        }
+    }
+}
+
+impl<T: 'static> Future for MustJoinHandle<T> {
+    type Output = T;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        match Pin::new(self.join_handle.as_mut().unwrap()).poll(cx) {
+            Poll::Ready(t) => {
+                if self.completed {
+                    panic!("should not poll completed join handle");
+                }
+                self.completed = true;
+                cfg_if! {
+                    if #[cfg(feature="rt-async-std")] {
+                        Poll::Ready(t)
+                    } else if #[cfg(feature="rt-tokio")] {
+                        match t {
+                            Ok(t) => Poll::Ready(t),
+                            Err(e) => {
+                                if e.is_panic() {
+                                    // Resume the panic on the main task
+                                    std::panic::resume_unwind(e.into_panic());
+                                } else {
+                                    panic!("join error was not a panic, should not poll after abort");
+                                }
+                            }
+                        }
+                    }else if #[cfg(target_arch = "wasm32")] {
+                        Poll::Ready(t)
+                    } else {
+                        compile_error!("needs executor implementation")
+                    }
+                }
+            }
+            Poll::Pending => Poll::Pending,
+        }
+    }
+}