From 8c4d1da7f7df439459492eed3222634e7cc19e2e Mon Sep 17 00:00:00 2001
From: Ben Dean-Kawamura <bdk@mozilla.com>
Date: Tue, 29 Aug 2023 11:11:18 -0400
Subject: [PATCH] Adding into_raw() and from_raw() methods

See issue #28.
---
 src/lib.rs   | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 tests/raw.rs | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 95 insertions(+)
 create mode 100644 tests/raw.rs

diff --git a/src/lib.rs b/src/lib.rs
index 7828e9f..14ea354 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -314,6 +314,31 @@ impl<T> Sender<T> {
             _ => unreachable!(),
         }
     }
+
+    /// Consumes the Sender, returning a raw pointer to the channel on the heap.
+    ///
+    /// This is intended to simplify using oneshot channels with some FFI code. The only safe thing
+    /// to do with the returned pointer is to later reconstruct the Sender with [Sender::from_raw].
+    /// Memory will leak if the Sender is never reconstructed.
+    pub fn into_raw(self) -> *mut () {
+        let raw = self.channel_ptr.as_ptr() as *mut ();
+        mem::forget(self);
+        raw
+    }
+
+    /// Consumes a raw pointer from [Sender::into_raw], recreating the Sender.
+    ///
+    /// # Safety
+    ///
+    /// This pointer must have come from [Sender::into_raw]. At most one Sender must exist for a
+    /// channel at any point in time. Constructing multiple Senders from the same raw pointer leads
+    /// to undefined behavior.
+    pub unsafe fn from_raw(raw: *mut ()) -> Self {
+        Self {
+            channel_ptr: NonNull::new_unchecked(raw as *mut Channel<T>),
+            _invariant: PhantomData,
+        }
+    }
 }
 
 impl<T> Drop for Sender<T> {
@@ -816,6 +841,30 @@ impl<T> Receiver<T> {
             _ => unreachable!(),
         }
     }
+
+    /// Consumes the Receiver, returning a raw pointer to the channel on the heap.
+    ///
+    /// This is intended to simplify using oneshot channels with some FFI code. The only safe thing
+    /// to do with the returned pointer is to later reconstruct the Receiver with
+    /// [Receiver::from_raw]. Memory will leak if the Receiver is never reconstructed.
+    pub fn into_raw(self) -> *mut () {
+        let raw = self.channel_ptr.as_ptr() as *mut ();
+        mem::forget(self);
+        raw
+    }
+
+    /// Consumes a raw pointer from [Receiver::into_raw], recreating the Receiver.
+    ///
+    /// # Safety
+    ///
+    /// This pointer must have come from [Receiver::into_raw]. At most one Receiver must exist for
+    /// a channel at any point in time. Constructing multiple Receiver from the same raw pointer
+    /// leads to undefined behavior.
+    pub unsafe fn from_raw(raw: *mut ()) -> Self {
+        Self {
+            channel_ptr: NonNull::new_unchecked(raw as *mut Channel<T>),
+        }
+    }
 }
 
 #[cfg(feature = "async")]
diff --git a/tests/raw.rs b/tests/raw.rs
new file mode 100644
index 0000000..e38dc45
--- /dev/null
+++ b/tests/raw.rs
@@ -0,0 +1,46 @@
+#![cfg(not(loom))]
+
+use oneshot::{channel, Receiver, Sender};
+
+#[test]
+fn test_raw_sender() {
+    let (sender, receiver) = channel::<u32>();
+    let raw = sender.into_raw();
+    let recreated = unsafe { Sender::<u32>::from_raw(raw) };
+    recreated
+        .send(100)
+        .unwrap_or_else(|e| panic!("error sending after into_raw/from_raw roundtrip: {e}"));
+    assert_eq!(receiver.try_recv(), Ok(100))
+}
+
+#[test]
+fn test_raw_receiver() {
+    let (sender, receiver) = channel::<u32>();
+    let raw = receiver.into_raw();
+    sender.send(100).unwrap();
+    let recreated = unsafe { Receiver::<u32>::from_raw(raw) };
+    assert_eq!(
+        recreated
+            .try_recv()
+            .unwrap_or_else(|e| panic!("error receiving after into_raw/from_raw roundtrip: {e}")),
+        100
+    )
+}
+
+#[test]
+fn test_raw_sender_and_receiver() {
+    let (sender, receiver) = channel::<u32>();
+    let raw_receiver = receiver.into_raw();
+    let raw_sender = sender.into_raw();
+
+    let recreated_sender = unsafe { Sender::<u32>::from_raw(raw_sender) };
+    recreated_sender.send(100).unwrap();
+
+    let recreated_receiver = unsafe { Receiver::<u32>::from_raw(raw_receiver) };
+    assert_eq!(
+        recreated_receiver
+            .try_recv()
+            .unwrap_or_else(|e| panic!("error receiving after into_raw/from_raw roundtrip: {e}")),
+        100
+    )
+}