Add abstract Transformer class

asm/src/main/java/dev/openrs2/asm/Transformer.java

@@ -0,0 +1,39 @@
+package dev.openrs2.asm;
+
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.tree.ClassNode;
+import org.objectweb.asm.tree.MethodNode;
+
+public abstract class Transformer {
+	public final void transform(Library library) {
+		preTransform(library);
+
+		for (var clazz : library) {
+			transformClass(clazz);
+
+			for (var method : clazz.methods) {
+				if ((method.access & (Opcodes.ACC_NATIVE | Opcodes.ACC_ABSTRACT)) == 0) {
+					transformMethod(clazz, method);
+				}
+			}
+		}
+
+		postTransform(library);
+	}
+
+	public void preTransform(Library library) {
+		/* empty */
+	}
+
+	public void transformClass(ClassNode clazz) {
+		/* empty */
+	}
+
+	public void transformMethod(ClassNode clazz, MethodNode method) {
+		/* empty */
+	}
+
+	public void postTransform(Library library) {
+		/* empty */
+	}
+}