feature: add a super simple oneshot channel

Author: tyrchen

Cargo.lock

@@ -7,4 +7,5 @@ edition = "2021"
 
 [dependencies]
 anyhow = "1.0.83"
+arc-swap = "1.7.1"
 crossbeam-channel = "0.5.12"

Cargo.toml

@@ -0,0 +1,99 @@
+use anyhow::Result;
+use arc_swap::ArcSwapOption;
+use std::thread;
+use std::{
+    ops::Deref,
+    sync::{
+        atomic::{AtomicBool, Ordering},
+        Arc,
+    },
+};
+
+struct Oneshot<T> {
+    data: ArcSwapOption<T>,
+    is_filled: AtomicBool,
+}
+
+struct Sender<T>(Arc<Oneshot<T>>);
+
+struct Receiver<T>(Arc<Oneshot<T>>);
+
+impl<T> Oneshot<T> {
+    fn channel() -> (Sender<T>, Receiver<T>) {
+        let oneshot = Arc::new(Oneshot {
+            data: ArcSwapOption::from(None),
+            is_filled: AtomicBool::new(false),
+        });
+        (Sender(oneshot.clone()), Receiver(oneshot))
+    }
+}
+
+impl<T> Sender<T> {
+    fn send(&self, value: T) -> Result<(), T> {
+        if self
+            .is_filled
+            .compare_exchange(false, true, Ordering::SeqCst, Ordering::SeqCst)
+            .is_ok()
+        {
+            self.data.store(Some(Arc::new(value)));
+            Ok(())
+        } else {
+            Err(value)
+        }
+    }
+}
+
+impl<T> Receiver<T> {
+    fn recv(&self) -> Result<T> {
+        if self
+            .is_filled
+            .compare_exchange(true, false, Ordering::SeqCst, Ordering::SeqCst)
+            .is_ok()
+        {
+            let v = self.data.swap(None);
+
+            v.ok_or_else(|| anyhow::anyhow!("No value"))
+                .and_then(|v| Arc::try_unwrap(v).map_err(|_| anyhow::anyhow!("Multiple receivers")))
+        } else {
+            Err(anyhow::anyhow!("Sender has not sent a value yet"))
+        }
+    }
+}
+
+impl<T> Deref for Receiver<T> {
+    type Target = Arc<Oneshot<T>>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl<T> Deref for Sender<T> {
+    type Target = Arc<Oneshot<T>>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+fn main() -> Result<()> {
+    let (tx, rx) = Oneshot::channel();
+
+    let sender_thread = thread::spawn(move || {
+        tx.send(42).unwrap();
+    });
+
+    let receiver_thread = thread::spawn(move || {
+        let Ok(v) = rx.recv() else {
+            eprintln!("Failed to receive value");
+            return;
+        };
+
+        println!("Received: {}", v);
+    });
+
+    sender_thread.join().unwrap();
+    receiver_thread.join().unwrap();
+
+    Ok(())
+}