2 files changed, 59 insertions, 7 deletions

diff --git a/third_party/rust/oneshot-uniffi/src/errors.rs b/third_party/rust/oneshot-uniffi/src/errors.rs
index afc48acd03..1fd0de1eed 100644
--- a/third_party/rust/oneshot-uniffi/src/errors.rs
+++ b/third_party/rust/oneshot-uniffi/src/errors.rs
@@ -4,7 +4,8 @@ use core::mem;
 use core::ptr::NonNull;
 
 /// An error returned when trying to send on a closed channel. Returned from
-/// [`Sender::send`] if the corresponding [`Receiver`] has already been dropped.
+/// [`Sender::send`](crate::Sender::send) if the corresponding [`Receiver`](crate::Receiver)
+/// has already been dropped.
 ///
 /// The message that could not be sent can be retreived again with [`SendError::into_inner`].
 pub struct SendError<T> {
@@ -79,10 +80,10 @@ impl<T> fmt::Debug for SendError<T> {
 #[cfg(feature = "std")]
 impl<T> std::error::Error for SendError<T> {}
 
-/// An error returned from the indefinitely blocking recv functions on a [`Receiver`].
+/// An error returned from the blocking [`Receiver::recv`](crate::Receiver::recv) method.
 ///
-/// The recv operation can only fail if the corresponding [`Sender`] was dropped before sending
-/// any message. Or if a message has already been sent and received on the channel.
+/// The receive operation can only fail if the corresponding [`Sender`](crate::Sender) was dropped
+/// before sending any message, or if a message has already been sent and received on the channel.
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
 pub struct RecvError;
 
@@ -95,7 +96,8 @@ impl fmt::Display for RecvError {
 #[cfg(feature = "std")]
 impl std::error::Error for RecvError {}
 
-/// An error returned when trying a non blocking receive on a [`Receiver`].
+/// An error returned when failing to receive a message in the non-blocking
+/// [`Receiver::try_recv`](crate::Receiver::try_recv).
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
 pub enum TryRecvError {
     /// The channel is still open, but there was no message present in it.
@@ -119,7 +121,8 @@ impl fmt::Display for TryRecvError {
 #[cfg(feature = "std")]
 impl std::error::Error for TryRecvError {}
 
-/// An error returned when trying a time limited blocking receive on a [`Receiver`].
+/// An error returned when failing to receive a message in
+/// [`Receiver::recv_timeout`](crate::Receiver::recv_timeout).
 #[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
 pub enum RecvTimeoutError {
     /// No message arrived on the channel before the timeout was reached. The channel is still open.
diff --git a/third_party/rust/oneshot-uniffi/src/lib.rs b/third_party/rust/oneshot-uniffi/src/lib.rs
index 94bb35d12a..8da012b8c0 100644
--- a/third_party/rust/oneshot-uniffi/src/lib.rs
+++ b/third_party/rust/oneshot-uniffi/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<T>::into_raw`] with the same message type, `T`.
+    /// 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<T>::into_raw`] with the same message type, `T`.
+    /// At most one Receiver must exist for a channel at any point in time.
+    /// Constructing multiple Receivers 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")]
@@ -1178,7 +1227,7 @@ fn receiver_waker_size() {
         (false, false) => 0,
         (false, true) => 16,
         (true, false) => 8,
-        (true, true) => 24,
+        (true, true) => 16,
     };
     assert_eq!(mem::size_of::<ReceiverWaker>(), expected);
 }