Change EntryHook API to take an enum instead of a bool

Besides more readability, this will help in a followup CL where we need
to add a new behavior.

Bug: N/A
Test: Covered by existing

Change-Id: If6caf171abe1dc88650dc72a633faeee6fb53ee9

3 files changed, 32 insertions, 15 deletions

diff --git a/dexter/experimental.cc b/dexter/experimental.cc
index 97a126a..545a340 100644
--- a/dexter/experimental.cc
+++ b/dexter/experimental.cc
@@ -291,8 +291,11 @@ void StressExitHook(std::shared_ptr<ir::DexFile> dex_ir) {
 // Test slicer::MethodInstrumenter
 void TestMethodInstrumenter(std::shared_ptr<ir::DexFile> dex_ir) {
   slicer::MethodInstrumenter mi(dex_ir);
-  mi.AddTransformation<slicer::EntryHook>(ir::MethodId("LTracer;", "onFooEntry"), true);
-  mi.AddTransformation<slicer::EntryHook>(ir::MethodId("LTracer;", "onFooEntry"), false);
+  mi.AddTransformation<slicer::EntryHook>(
+      ir::MethodId("LTracer;", "onFooEntry"),
+      slicer::EntryHook::Tweak::ThisAsObject);
+  mi.AddTransformation<slicer::EntryHook>(
+      ir::MethodId("LTracer;", "onFooEntry"));
   mi.AddTransformation<slicer::ExitHook>(ir::MethodId("LTracer;", "onFooExit"));
   mi.AddTransformation<slicer::DetourVirtualInvoke>(
       ir::MethodId("LBase;", "foo", "(ILjava/lang/String;)I"),
diff --git a/slicer/export/slicer/instrumentation.h b/slicer/export/slicer/instrumentation.h
index c6ad454..b9fda8c 100644
--- a/slicer/export/slicer/instrumentation.h
+++ b/slicer/export/slicer/instrumentation.h
@@ -40,23 +40,34 @@ class Transformation {
 // an explicit "this" argument for non-static methods.
 class EntryHook : public Transformation {
  public:
-  explicit EntryHook(
-      const ir::MethodId& hook_method_id,
-      bool use_object_type_for_this_argument = false)
-      : hook_method_id_(hook_method_id),
-        use_object_type_for_this_argument_(use_object_type_for_this_argument) {
+  enum class Tweak {
+    None,
+    // Expose the "this" argument of non-static methods as the "Object" type.
+    // This can be helpful when the code you want to handle the hook doesn't
+    // have access to the actual type in its classpath.
+    ThisAsObject
+  };
+
+  explicit EntryHook(const ir::MethodId& hook_method_id, Tweak tweak)
+      : hook_method_id_(hook_method_id), tweak_(tweak) {
     // hook method signature is generated automatically
     SLICER_CHECK(hook_method_id_.signature == nullptr);
   }
 
+  // TODO: Delete this legacy constrcutor.
+  // It is left in temporarily so we can move callers away from it to the new
+  // `tweak` constructor.
+  explicit EntryHook(const ir::MethodId& hook_method_id,
+                     bool use_object_type_for_this_argument = false)
+      : EntryHook(hook_method_id, use_object_type_for_this_argument
+                                      ? Tweak::ThisAsObject
+                                      : Tweak::None) {}
+
   virtual bool Apply(lir::CodeIr* code_ir) override;
 
  private:
   ir::MethodId hook_method_id_;
-  // If true, "this" argument of non-static methods is forwarded as Object type.
-  // For example "this" argument of OkHttpClient type is forwared as Object and
-  // is used to get OkHttp class loader.
-  bool use_object_type_for_this_argument_;
+  Tweak tweak_;
 };
 
 // Insert a call to the "exit hook" method before every return
diff --git a/slicer/instrumentation.cc b/slicer/instrumentation.cc
index 0781594..83a524d 100644
--- a/slicer/instrumentation.cc
+++ b/slicer/instrumentation.cc
@@ -39,10 +39,13 @@ bool EntryHook::Apply(lir::CodeIr* code_ir) {
   std::vector<ir::Type*> param_types;
   if ((ir_method->access_flags & dex::kAccStatic) == 0) {
     ir::Type* this_argument_type;
-    if (use_object_type_for_this_argument_) {
-      this_argument_type = builder.GetType("Ljava/lang/Object;");
-    } else {
-      this_argument_type = ir_method->decl->parent;
+    switch (tweak_) {
+      case Tweak::ThisAsObject:
+        this_argument_type = builder.GetType("Ljava/lang/Object;");
+        break;
+      default:
+        this_argument_type = ir_method->decl->parent;
+        break;
     }
     param_types.push_back(this_argument_type);
   }