keep long returning memory address func in base SwiftInstance

Author: ktoso

SwiftKitCore/src/main/java/org/swift/swiftkit/core/JNISwiftInstance.java

@@ -38,6 +38,11 @@ protected JNISwiftInstance(long pointer, SwiftArena arena) {
         this.selfPointer = pointer;
     }
 
+    @Override
+    public long $memoryAddress() {
+        return selfPointer;
+    }
+
     /**
      * Creates a function that will be called when the value should be destroyed.
      * This will be code-generated to call a native method to do deinitialization and deallocation.

SwiftKitCore/src/main/java/org/swift/swiftkit/core/SwiftInstance.java

@@ -18,6 +18,24 @@
 
 public abstract class SwiftInstance {
 
+    /**
+     * The designated constructor of any imported Swift types.
+     *
+     * @param arena the arena this object belongs to. When the arena goes out of scope, this value is destroyed.
+     */
+    protected SwiftInstance(SwiftArena arena) {
+        arena.register(this);
+    }
+
+    /**
+     * Pointer to the {@code self} of the underlying Swift object or value.
+     *
+     * @apiNote When using this pointer one must ensure that the underlying object
+     *          is kept alive using some means (e.g. a class remains retained), as
+     *          this function does not ensure safety of the address in any way.
+     */
+    public abstract long $memoryAddress();
+
     /**
      * Called when the arena has decided the value should be destroyed.
      * <p/>
@@ -34,22 +52,12 @@ public abstract class SwiftInstance {
      * <p/>
      * This is exposing the object, rather than performing the action because we don't want to accidentally
      * form a strong reference to the {@code SwiftInstance} which could prevent the cleanup from running,
-     * if using an GC managed instance (e.g. using an {@link AutoSwiftMemorySession}.
+     * if using an GC managed instance (e.g. using an {@code AutoSwiftMemorySession}.
      */
     public final AtomicBoolean $statusDestroyedFlag() {
         return this.$state$destroyed;
     }
 
-    /**
-     * The designated constructor of any imported Swift types.
-     *
-     * @param pointer a pointer to the memory containing the value
-     * @param arena the arena this object belongs to. When the arena goes out of scope, this value is destroyed.
-     */
-    protected SwiftInstance(SwiftArena arena) {
-        arena.register(this);
-    }
-
     /**
      * Ensures that this instance has not been destroyed.
      * <p/>

SwiftKitFFM/src/main/java/org/swift/swiftkit/ffm/FFMSwiftInstance.java

@@ -22,28 +22,34 @@
 public abstract class FFMSwiftInstance extends SwiftInstance {
     private final MemorySegment memorySegment;
 
+    /**
+     * The designated constructor of any imported Swift types.
+     *
+     * @param segment the memory segment.
+     * @param arena the arena this object belongs to. When the arena goes out of scope, this value is destroyed.
+     */
+    protected FFMSwiftInstance(MemorySegment segment, AllocatingSwiftArena arena) {
+        super(arena);
+        this.memorySegment = segment;
+    }
+
     /**
      * The pointer to the instance in memory. I.e. the {@code self} of the Swift object or value.
      */
     public final MemorySegment $memorySegment() {
         return this.memorySegment;
     }
 
+    @Override
+    public long $memoryAddress() {
+        return $memorySegment().address();
+    }
+
     /**
      * The Swift type metadata of this type.
      */
     public abstract SwiftAnyType $swiftType();
 
-    /**
-     * The designated constructor of any imported Swift types.
-     *
-     * @param segment the memory segment.
-     * @param arena the arena this object belongs to. When the arena goes out of scope, this value is destroyed.
-     */
-    protected FFMSwiftInstance(MemorySegment segment, AllocatingSwiftArena arena) {
-        super(arena);
-        this.memorySegment = segment;
-    }
 
     @Override
     public SwiftInstanceCleanup createCleanupAction() {