Complete refactor of the FFI to use handles instead of pointers.

src/static_data/libraries/data_library.rs

@@ -15,13 +15,17 @@ pub trait DataLibrary<T: ?Sized> {
     fn get_modify(&mut self) -> &mut IndexMap<StringKey, Arc<T>>;
 
     /// Adds a new value to the library.
-    fn add(&mut self, key: &StringKey, value: Arc<T>) {
-        self.get_modify().insert(key.clone(), value);
+    fn add(&self, key: &StringKey, value: Arc<T>) {
+        #[allow(clippy::unwrap_used)] // We know this cant fail.
+        let self_mut = unsafe { (self as *const Self as *mut Self).as_mut() }.unwrap();
+        self_mut.get_modify().insert(key.clone(), value);
     }
 
     /// Removes a value from the library.
-    fn remove(&mut self, key: &StringKey) {
-        self.get_modify().remove(key);
+    fn remove(&self, key: &StringKey) {
+        #[allow(clippy::unwrap_used)] // We know this cant fail.
+        let self_mut = unsafe { (self as *const Self as *mut Self).as_mut() }.unwrap();
+        self_mut.get_modify().remove(key);
     }
 
     /// Gets a value from the library.