feat(api): [core] add Addressable

modules/overrungl.core/src/main/java/overrungl/struct/Struct.java

@@ -16,6 +16,7 @@
 
 package overrungl.struct;
 
+import overrungl.util.Addressable;
 import overrungl.util.Unmarshal;
 
 import java.lang.foreign.MemorySegment;
@@ -29,7 +30,7 @@
 ///
 /// @author squid233
 /// @since 0.1.0
-public abstract class Struct {
+public abstract class Struct implements Addressable {
     private final MemorySegment segment;
     private final StructLayout layout;
 
@@ -64,6 +65,7 @@ public long estimateCount() {
     }
 
     /// {@return the segment of this struct}
+    @Override
     public MemorySegment segment() {
         return segment;
     }

modules/overrungl.core/src/main/java/overrungl/struct/Union.java

@@ -16,6 +16,7 @@
 
 package overrungl.struct;
 
+import overrungl.util.Addressable;
 import overrungl.util.Unmarshal;
 
 import java.lang.foreign.MemorySegment;
@@ -25,7 +26,7 @@
 ///
 /// @author squid233
 /// @since 0.1.0
-public abstract class Union {
+public abstract class Union implements Addressable {
     private final MemorySegment segment;
     private final UnionLayout layout;
 
@@ -60,6 +61,7 @@ public long estimateCount() {
     }
 
     /// {@return the segment of this union}
+    @Override
     public MemorySegment segment() {
         return segment;
     }

modules/overrungl.core/src/main/java/overrungl/util/Addressable.java

@@ -0,0 +1,28 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2025 Overrun Organization
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ */
+
+package overrungl.util;
+
+import java.lang.foreign.MemorySegment;
+
+/// An instance that holds a [MemorySegment].
+///
+/// @author squid233
+/// @since 0.1.0
+public interface Addressable {
+    /// {@return the segment of this instance}
+    MemorySegment segment();
+}

modules/overrungl.core/src/main/java/overrungl/util/Marshal.java

@@ -1,7 +1,7 @@
 /*
  * MIT License
  *
- * Copyright (c) 2024 Overrun Organization
+ * Copyright (c) 2024-2025 Overrun Organization
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -17,7 +17,6 @@
 package overrungl.util;
 
 import org.jetbrains.annotations.Nullable;
-import overrungl.struct.Struct;
 import overrungl.upcall.Upcall;
 
 import java.lang.foreign.Arena;
@@ -64,14 +63,14 @@ public static MemorySegment marshal(SegmentAllocator allocator, @Nullable String
     }
 
     /**
-     * Converts the given struct to a segment.
+     * Converts the given addressable object to a segment.
      *
-     * @param struct the struct
+     * @param addressable the addressable object
      * @return the segment
      */
-    public static MemorySegment marshal(@Nullable Struct struct) {
-        if (struct == null) return MemorySegment.NULL;
-        return struct.segment();
+    public static MemorySegment marshal(@Nullable Addressable addressable) {
+        if (addressable == null) return MemorySegment.NULL;
+        return addressable.segment();
     }
 
     /**