1 files changed, 51 insertions, 0 deletions
diff --git a/third_party/rust/tokio/src/util/atomic_cell.rs b/third_party/rust/tokio/src/util/atomic_cell.rs
new file mode 100644
index 0000000000..07e37303a7
--- /dev/null
+++ b/third_party/rust/tokio/src/util/atomic_cell.rs
@@ -0,0 +1,51 @@
+use crate::loom::sync::atomic::AtomicPtr;
+
+use std::ptr;
+use std::sync::atomic::Ordering::AcqRel;
+
+pub(crate) struct AtomicCell<T> {
+    data: AtomicPtr<T>,
+}
+
+unsafe impl<T: Send> Send for AtomicCell<T> {}
+unsafe impl<T: Send> Sync for AtomicCell<T> {}
+
+impl<T> AtomicCell<T> {
+    pub(crate) fn new(data: Option<Box<T>>) -> AtomicCell<T> {
+        AtomicCell {
+            data: AtomicPtr::new(to_raw(data)),
+        }
+    }
+
+    pub(crate) fn swap(&self, val: Option<Box<T>>) -> Option<Box<T>> {
+        let old = self.data.swap(to_raw(val), AcqRel);
+        from_raw(old)
+    }
+
+    pub(crate) fn set(&self, val: Box<T>) {
+        let _ = self.swap(Some(val));
+    }
+
+    pub(crate) fn take(&self) -> Option<Box<T>> {
+        self.swap(None)
+    }
+}
+
+fn to_raw<T>(data: Option<Box<T>>) -> *mut T {
+    data.map(Box::into_raw).unwrap_or(ptr::null_mut())
+}
+
+fn from_raw<T>(val: *mut T) -> Option<Box<T>> {
+    if val.is_null() {
+        None
+    } else {
+        Some(unsafe { Box::from_raw(val) })
+    }
+}
+
+impl<T> Drop for AtomicCell<T> {
+    fn drop(&mut self) {
+        // Free any data still held by the cell
+        let _ = self.take();
+    }
+}