Rework of FFI, adding a value identifier, so we can keep knowledge of data even when data moves.

src/utils/value_identifier.rs

@@ -0,0 +1,22 @@
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+static CURRENT: AtomicUsize = AtomicUsize::new(1);
+
+/// An extremely basic way to identify a piece of data.
+#[derive(Debug, Copy, Clone, Ord, PartialOrd, Eq, PartialEq)]
+#[repr(C)]
+pub struct ValueIdentifier(usize);
+
+impl Default for ValueIdentifier {
+    fn default() -> Self {
+        Self {
+            0: CURRENT.fetch_add(1, Ordering::SeqCst),
+        }
+    }
+}
+
+/// An object with a specific identifier.
+pub trait ValueIdentifiable {
+    /// Get the identifier for the current object.
+    fn value_identifier(&self) -> ValueIdentifier;
+}