Add FieldOrderTransformer

deob/src/main/java/dev/openrs2/deob/Deobfuscator.java

@@ -15,6 +15,7 @@ import dev.openrs2.deob.transform.CanvasTransformer;
 import dev.openrs2.deob.transform.ClassForNameTransformer;
 import dev.openrs2.deob.transform.CounterTransformer;
 import dev.openrs2.deob.transform.ExceptionTracingTransformer;
+import dev.openrs2.deob.transform.FieldOrderTransformer;
 import dev.openrs2.deob.transform.OpaquePredicateTransformer;
 import dev.openrs2.deob.transform.OriginalNameTransformer;
 import org.slf4j.Logger;
@@ -27,7 +28,8 @@ public final class Deobfuscator {
 		new OpaquePredicateTransformer(),
 		new ExceptionTracingTransformer(),
 		new CounterTransformer(),
-		new CanvasTransformer()
+		new CanvasTransformer(),
+		new FieldOrderTransformer()
 	);
 
 	public static void main(String[] args) throws IOException {

deob/src/main/java/dev/openrs2/deob/transform/FieldOrderTransformer.java

@@ -0,0 +1,52 @@
+package dev.openrs2.deob.transform;
+
+import java.util.HashMap;
+
+import dev.openrs2.asm.MemberDesc;
+import dev.openrs2.asm.Transformer;
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.tree.ClassNode;
+import org.objectweb.asm.tree.FieldInsnNode;
+
+public final class FieldOrderTransformer extends Transformer {
+	private static final String CONSTRUCTOR = "<init>";
+	private static final String STATIC_CONSTRUCTOR = "<clinit>";
+
+	private static void sortFields(ClassNode clazz, String ctorName, int opcode) {
+		clazz.methods.stream()
+			.filter(m -> m.name.equals(ctorName))
+			.findFirst()
+			.ifPresent(ctor -> {
+				var fields = new HashMap<MemberDesc, Integer>();
+				var index = 0;
+
+				for (var insn = ctor.instructions.getFirst(); insn != null; insn = insn.getNext()) {
+					if (insn.getOpcode() != opcode) {
+						continue;
+					}
+
+					var putfield = (FieldInsnNode) insn;
+					if (!putfield.owner.equals(clazz.name)) {
+						continue;
+					}
+
+					var desc = new MemberDesc(putfield.name, putfield.desc);
+					if (!fields.containsKey(desc)) {
+						fields.put(desc, index++);
+					}
+				}
+
+				clazz.fields.sort((a, b) -> {
+					var indexA = fields.getOrDefault(new MemberDesc(a.name, a.desc), -1);
+					var indexB = fields.getOrDefault(new MemberDesc(b.name, b.desc), -1);
+					return Integer.compare(indexA, indexB);
+				});
+			});
+	}
+
+	@Override
+	public void transformClass(ClassNode clazz) {
+		sortFields(clazz, CONSTRUCTOR, Opcodes.PUTFIELD);
+		sortFields(clazz, STATIC_CONSTRUCTOR, Opcodes.PUTSTATIC);
+	}
+}