Restructured the source code in the Playdate bindings target.

Sources/PlaydateKit/Lua/Structures/UDObject.swift

@@ -0,0 +1,32 @@
+internal import CPlaydate
+
+extension Lua {
+    /// A handle to a Lua-owned object. Wraps `LuaUDObject`.
+    public struct UDObject {
+        let pointer: OpaquePointer
+
+        /// Prevents the object from being garbage-collected until `release()`.
+        @discardableResult
+        public func retain() -> UDObject {
+            UDObject(pointer: luaAPI.pointee.retainObject.unsafelyUnwrapped(pointer).unsafelyUnwrapped)
+        }
+
+        public func release() {
+            luaAPI.pointee.releaseObject.unsafelyUnwrapped(pointer)
+        }
+
+        /// Pops the value on top of the stack and stores it in the object's
+        /// user-value `slot` (1-based).
+        public func setUserValue(slot: UInt32) {
+            luaAPI.pointee.setUserValue.unsafelyUnwrapped(pointer, slot)
+        }
+
+        /// Pushes the value in user-value `slot` onto the stack and returns
+        /// its stack position, or `nil` if there is none.
+        @discardableResult
+        public func getUserValue(slot: UInt32) -> Int? {
+            let position = luaAPI.pointee.getUserValue.unsafelyUnwrapped(pointer, slot)
+            return position == 0 ? nil : Int(position)
+        }
+    }
+}