initial import of main veilid core

veilid-core/src/xx/single_shot_eventual.rs

@@ -0,0 +1,39 @@
+use super::*;
+
+pub struct SingleShotEventual<T>
+where
+    T: Unpin + Clone,
+{
+    eventual: EventualValueClone<T>,
+    drop_value: T,
+}
+
+impl<T> Drop for SingleShotEventual<T>
+where
+    T: Unpin + Clone,
+{
+    fn drop(&mut self) {
+        self.eventual.resolve(self.drop_value.clone());
+    }
+}
+
+impl<T> SingleShotEventual<T>
+where
+    T: Unpin + Clone,
+{
+    pub fn new(drop_value: T) -> Self {
+        Self {
+            eventual: EventualValueClone::new(),
+            drop_value: drop_value,
+        }
+    }
+
+    // Can only call this once, it consumes the eventual
+    pub fn resolve(self, value: T) -> EventualResolvedFuture<EventualValueClone<T>> {
+        self.eventual.resolve(value)
+    }
+
+    pub fn instance(&self) -> EventualValueCloneFuture<T> {
+        self.eventual.instance()
+    }
+}