Add CounterTransformer

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

@@ -15,6 +15,7 @@ import dev.openrs2.deob.classpath.ClassPath;
 import dev.openrs2.deob.classpath.TypedRemapper;
 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.OpaquePredicateTransformer;
 import dev.openrs2.deob.transform.OriginalNameTransformer;
@@ -27,6 +28,7 @@ public final class Deobfuscator {
 	private static final List<Transformer> TRANSFORMERS = List.of(
 		new OpaquePredicateTransformer(),
 		new ExceptionTracingTransformer(),
+		new CounterTransformer(),
 		new CanvasTransformer()
 	);
 

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

@@ -0,0 +1,118 @@
+package dev.openrs2.deob.transform;
+
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+import dev.openrs2.asm.InsnMatcher;
+import dev.openrs2.asm.Library;
+import dev.openrs2.asm.MemberRef;
+import dev.openrs2.asm.Transformer;
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.tree.AbstractInsnNode;
+import org.objectweb.asm.tree.ClassNode;
+import org.objectweb.asm.tree.FieldInsnNode;
+import org.objectweb.asm.tree.MethodNode;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public final class CounterTransformer extends Transformer {
+	private static final Logger logger = LoggerFactory.getLogger(CounterTransformer.class);
+
+	private static final InsnMatcher RESET_PATTERN = InsnMatcher.compile("ICONST_0 PUTSTATIC");
+	private static final InsnMatcher INCREMENT_PATTERN = InsnMatcher.compile("GETSTATIC ICONST_1 IADD PUTSTATIC");
+
+	private final Set<MemberRef> counters = new HashSet<>();
+
+	@Override
+	public void preTransform(Library library) {
+		counters.clear();
+
+		var references = new HashMap<MemberRef, Integer>();
+		var resets = new HashMap<MemberRef, Integer>();
+		var increments = new HashMap<MemberRef, Integer>();
+
+		for (var clazz : library) {
+			for (var method : clazz.methods) {
+				if ((method.access & (Opcodes.ACC_NATIVE | Opcodes.ACC_ABSTRACT)) == 0) {
+					findCounters(method, references, resets, increments);
+				}
+			}
+		}
+
+		deleteCounters(library, references, resets, increments);
+	}
+
+	private void findCounters(MethodNode method, Map<MemberRef, Integer> references, Map<MemberRef, Integer> resets, Map<MemberRef, Integer> increments) {
+		for (var insn = method.instructions.getFirst(); insn != null; insn = insn.getNext()) {
+			if (insn.getType() != AbstractInsnNode.FIELD_INSN) {
+				continue;
+			}
+
+			var fieldInsn = (FieldInsnNode) insn;
+			references.merge(new MemberRef(fieldInsn.owner, fieldInsn.name, fieldInsn.desc), 1, Integer::sum);
+		}
+
+		RESET_PATTERN.match(method).forEach(match -> {
+			var putstatic = (FieldInsnNode) match.get(1);
+			resets.merge(new MemberRef(putstatic.owner, putstatic.name, putstatic.desc), 1, Integer::sum);
+		});
+
+		INCREMENT_PATTERN.match(method).forEach(match -> {
+			var getstatic = (FieldInsnNode) match.get(0);
+			var putstatic = (FieldInsnNode) match.get(3);
+			if (getstatic.owner.equals(putstatic.owner) && getstatic.name.equals(putstatic.name) && getstatic.desc.equals(putstatic.desc)) {
+				increments.merge(new MemberRef(putstatic.owner, putstatic.name, putstatic.desc), 1, Integer::sum);
+			}
+		});
+	}
+
+	private void deleteCounters(Library library, Map<MemberRef, Integer> references, Map<MemberRef, Integer> resets, Map<MemberRef, Integer> increments) {
+		for (Map.Entry<MemberRef, Integer> entry : references.entrySet()) {
+			var counter = entry.getKey();
+
+			if (entry.getValue() != 3) { /* one for the reset, two for the increment */
+				continue;
+			}
+
+			if (resets.getOrDefault(counter, 0) != 1) {
+				continue;
+			}
+
+			if (increments.getOrDefault(counter, 0) != 1) {
+				continue;
+			}
+
+			ClassNode owner = library.get(counter.getOwner());
+			owner.fields.removeIf(f -> f.name.equals(counter.getName()) && f.desc.equals(counter.getDesc()));
+
+			counters.add(counter);
+		}
+	}
+
+	@Override
+	public void transformCode(ClassNode clazz, MethodNode method) {
+		RESET_PATTERN.match(method).forEach(match -> {
+			var putstatic = (FieldInsnNode) match.get(1);
+			if (counters.contains(new MemberRef(putstatic.owner, putstatic.name, putstatic.desc))) {
+				match.forEach(method.instructions::remove);
+			}
+		});
+
+		INCREMENT_PATTERN.match(method).forEach(match -> {
+			var getstatic = (FieldInsnNode) match.get(0);
+			var putstatic = (FieldInsnNode) match.get(3);
+
+			if (getstatic.owner.equals(putstatic.owner) && getstatic.name.equals(putstatic.name) && getstatic.desc.equals(putstatic.desc) &&
+					counters.contains(new MemberRef(putstatic.owner, putstatic.name, putstatic.desc))) {
+				match.forEach(method.instructions::remove);
+			}
+		});
+	}
+
+	@Override
+	public void postTransform(Library library) {
+		logger.info("Removed {} counters", counters.size());
+	}
+}