Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 77 insertions, 0 deletions

diff --git a/third_party/rust/tokio/src/macros/scoped_tls.rs b/third_party/rust/tokio/src/macros/scoped_tls.rs
new file mode 100644
index 0000000000..f2504cbadf
--- /dev/null
+++ b/third_party/rust/tokio/src/macros/scoped_tls.rs
@@ -0,0 +1,77 @@
+use crate::loom::thread::LocalKey;
+
+use std::cell::Cell;
+use std::marker;
+
+/// Sets a reference as a thread-local.
+macro_rules! scoped_thread_local {
+    ($(#[$attrs:meta])* $vis:vis static $name:ident: $ty:ty) => (
+        $(#[$attrs])*
+        $vis static $name: $crate::macros::scoped_tls::ScopedKey<$ty>
+            = $crate::macros::scoped_tls::ScopedKey {
+                inner: {
+                    thread_local!(static FOO: ::std::cell::Cell<*const ()> = {
+                        std::cell::Cell::new(::std::ptr::null())
+                    });
+                    &FOO
+                },
+                _marker: ::std::marker::PhantomData,
+            };
+    )
+}
+
+/// Type representing a thread local storage key corresponding to a reference
+/// to the type parameter `T`.
+pub(crate) struct ScopedKey<T> {
+    pub(crate) inner: &'static LocalKey<Cell<*const ()>>,
+    pub(crate) _marker: marker::PhantomData<T>,
+}
+
+unsafe impl<T> Sync for ScopedKey<T> {}
+
+impl<T> ScopedKey<T> {
+    /// Inserts a value into this scoped thread local storage slot for a
+    /// duration of a closure.
+    pub(crate) fn set<F, R>(&'static self, t: &T, f: F) -> R
+    where
+        F: FnOnce() -> R,
+    {
+        struct Reset {
+            key: &'static LocalKey<Cell<*const ()>>,
+            val: *const (),
+        }
+
+        impl Drop for Reset {
+            fn drop(&mut self) {
+                self.key.with(|c| c.set(self.val));
+            }
+        }
+
+        let prev = self.inner.with(|c| {
+            let prev = c.get();
+            c.set(t as *const _ as *const ());
+            prev
+        });
+
+        let _reset = Reset {
+            key: self.inner,
+            val: prev,
+        };
+
+        f()
+    }
+
+    /// Gets a value out of this scoped variable.
+    pub(crate) fn with<F, R>(&'static self, f: F) -> R
+    where
+        F: FnOnce(Option<&T>) -> R,
+    {
+        let val = self.inner.with(|c| c.get());
+
+        if val.is_null() {
+            f(None)
+        } else {
+            unsafe { f(Some(&*(val as *const T))) }
+        }
+    }
+}