Implement instanceof checks. (#23)

runtime/src/main/cpp/Memory.cpp

@@ -74,11 +74,31 @@ void* AllocInstance(const TypeInfo* type_info, PlacementHint hint) {
   return ObjectContainer(type_info).GetPlace();
 }
 
-void* AllocArrayInstance(const TypeInfo* type_info, PlacementHint hint, uint32_t elements) {
+void* AllocArrayInstance(
+    const TypeInfo* type_info, PlacementHint hint, uint32_t elements) {
   RuntimeAssert(type_info->instanceSize_ < 0, "must be an array");
   return ArrayContainer(type_info, elements).GetPlace();
 }
 
+int IsInstance(const ObjHeader* obj, const TypeInfo* type_info) {
+  // We assume null check is handled by caller.
+  RuntimeAssert(obj != nullptr, "must not be null");
+  const TypeInfo* obj_type_info = obj->type_info();
+  // If it is an interface - check in list of implemented interfaces.
+  if (type_info->fieldsCount_ < 0) {
+    for (int i = 0; i < obj_type_info->implementedInterfacesCount_; ++i) {
+      if (obj_type_info->implementedInterfaces_[i] == type_info) {
+        return 1;
+      }
+    }
+    return 0;
+  }
+  while (obj_type_info != nullptr && obj_type_info != type_info) {
+    obj_type_info = obj_type_info->superType_;
+  }
+  return obj_type_info != nullptr;
+}
+
 #ifdef __cplusplus
 }
 #endif

runtime/src/main/cpp/Memory.h

@@ -260,6 +260,7 @@ extern "C" {
 void InitMemory();
 void* AllocInstance(const TypeInfo* type_info, PlacementHint hint);
 void* AllocArrayInstance(const TypeInfo* type_info, PlacementHint hint, uint32_t elements);
+int IsInstance(const ObjHeader* obj, const TypeInfo* type_info);
 
 #ifdef __cplusplus
 }

runtime/src/main/cpp/TypeInfo.h

@@ -28,15 +28,17 @@ struct TypeInfo {
     // Must be pointer to Any for array classes, and null for Any.
     const TypeInfo* superType_;
     // All object references inside this object.
-    const int* objOffsets_;
+    const int32_t* objOffsets_;
-    int objOffsetsCount_;
+    int32_t objOffsetsCount_;
     const TypeInfo* const* implementedInterfaces_;
-    int implementedInterfacesCount_;
+    int32_t implementedInterfacesCount_;
-    void* const* vtable_; // TODO: place vtable at the end of TypeInfo to eliminate the indirection
+    // TODO: place vtable at the end of TypeInfo to eliminate the indirection.
+    void* const* vtable_;
     const MethodTableRecord* openMethods_;
     uint32_t openMethodsCount_;
     const FieldTableRecord* fields_;
-    uint32_t fieldsCount_;
+    // Is negative to mark an interface.
+    int32_t fieldsCount_;
 };
 
 #ifdef __cplusplus