feat: EmptyArrayLengthTransformer

deobfuscator-transformers/src/main/java/uwu/narumi/deobfuscator/core/other/impl/universal/UniversalNumberTransformer.java

@@ -2,7 +2,7 @@
 
 import uwu.narumi.deobfuscator.api.transformer.ComposedTransformer;
 import uwu.narumi.deobfuscator.core.other.impl.clean.peephole.UselessPopCleanTransformer;
-import uwu.narumi.deobfuscator.core.other.impl.universal.number.InlineConstantValuesTransformer;
+import uwu.narumi.deobfuscator.core.other.impl.universal.number.*;
 
 /**
  * Simplifies number operations on constant values.
@@ -11,6 +11,7 @@ public class UniversalNumberTransformer extends ComposedTransformer {
   public UniversalNumberTransformer() {
     super(
         InlineConstantValuesTransformer::new,
+        EmptyArrayLengthTransformer::new,
 
         UselessPopCleanTransformer::new
     );

deobfuscator-transformers/src/main/java/uwu/narumi/deobfuscator/core/other/impl/universal/number/EmptyArrayLengthTransformer.java

@@ -0,0 +1,49 @@
+package uwu.narumi.deobfuscator.core.other.impl.universal.number;
+
+import org.objectweb.asm.tree.*;
+import uwu.narumi.deobfuscator.api.helper.AsmHelper;
+import uwu.narumi.deobfuscator.api.transformer.Transformer;
+
+public class EmptyArrayLengthTransformer extends Transformer {
+  @Override
+  protected void transform() throws Exception {
+    scopedClasses().parallelStream()
+      .forEach(classWrapper -> classWrapper.methods().parallelStream().forEach(methodNode -> {
+        InsnList list = methodNode.instructions;
+        list.forEach(insn -> {
+          if (insn.getOpcode() == ARRAYLENGTH) {
+            AbstractInsnNode arrayInsn = insn.getPrevious();
+            if (arrayInsn != null && arrayInsn.getOpcode() == NEWARRAY) {
+              AbstractInsnNode sizeInsn = arrayInsn.getPrevious();
+              Integer constValue = getInt(sizeInsn);
+              if (constValue != null) {
+                list.set(insn, AsmHelper.numberInsn(constValue));
+                list.remove(arrayInsn);
+                list.remove(sizeInsn);
+              }
+            }
+          }
+        });
+      }));
+  }
+
+  private Integer getInt(AbstractInsnNode insn) {
+    if (insn instanceof InsnNode) {
+      switch (insn.getOpcode()) {
+        case ICONST_M1: return -1;
+        case ICONST_0: return 0;
+        case ICONST_1: return 1;
+        case ICONST_2: return 2;
+        case ICONST_3: return 3;
+        case ICONST_4: return 4;
+        case ICONST_5: return 5;
+      }
+    } else if (insn instanceof IntInsnNode iinsn) {
+      return iinsn.operand;
+    } else if (insn instanceof LdcInsnNode linsn) {
+      Object cst = linsn.cst;
+      if (cst instanceof Integer) return (Integer) cst;
+    }
+    return null;
+  }
+}