Document ExceptionTracingTransformer

Signed-off-by: Graham <gpe@openrs2.dev>

deob/src/main/java/dev/openrs2/deob/transform/ExceptionTracingTransformer.kt

@@ -9,6 +9,24 @@ import dev.openrs2.asm.transform.Transformer
 import org.objectweb.asm.tree.ClassNode
 import org.objectweb.asm.tree.MethodNode
 
+/**
+ * A [Transformer] responsible for removing two kinds of redundant exception
+ * handler.
+ *
+ * - [ZKM](http://www.zelix.com/klassmaster/)'s
+ *   [exception obfuscation](https://www.zelix.com/klassmaster/featuresExceptionObfuscation.html),
+ *   which inserts exception handlers that catch [RuntimeException]s and
+ *   immediately re-throw them. The exception handlers are inserted in
+ *   locations where there is no Java source code equivalent, confusing
+ *   decompilers.
+ *
+ * - Jagex inserts a try/catch block around every method that catches
+ *   [RuntimeException]s, wraps them with a custom [RuntimeException]
+ *   implementation and re-throws them. The wrapped exception's message
+ *   contains the values of the method's arguments. While this is for debugging
+ *   and not obfuscation, it is clearly automatically-generated and thus we
+ *   remove these exception handlers too.
+ */
 class ExceptionTracingTransformer : Transformer() {
     private var tracingTryCatches = 0