1 files changed, 31 insertions, 0 deletions
diff --git a/vendor/regex-automata-0.2.0/src/util/lazy.rs b/vendor/regex-automata-0.2.0/src/util/lazy.rs
new file mode 100644
index 000000000..d8cac6ef4
--- /dev/null
+++ b/vendor/regex-automata-0.2.0/src/util/lazy.rs
@@ -0,0 +1,31 @@
+use core::{
+    cell::Cell,
+    ptr,
+    sync::atomic::{AtomicPtr, Ordering},
+};
+
+use alloc::{boxed::Box, vec::Vec};
+
+#[inline(always)]
+pub(crate) fn get_or_init<T: Send + Sync + 'static>(
+    location: &'static AtomicPtr<T>,
+    init: impl FnOnce() -> T,
+) -> &'static T {
+    let mut ptr = location.load(Ordering::Acquire);
+    if ptr.is_null() {
+        let new_dfa = Box::new(init());
+        ptr = Box::into_raw(new_dfa);
+        let result = location.compare_exchange(
+            ptr::null_mut(),
+            ptr,
+            Ordering::AcqRel,
+            Ordering::Acquire,
+        );
+        if let Err(old) = result {
+            let redundant = unsafe { Box::from_raw(ptr) };
+            drop(redundant);
+            ptr = old;
+        }
+    }
+    unsafe { &*ptr }
+}