[v8-users] How to wrap c++ obj during initialization and unwrap during binded function callback ??

[Sudheer Kumar]

Hello everyone,
   I am struggling wrapping and unwrapping the c++ object (MYCLASS) . below 
is the sample code i have written for my exact requirement:


  void Update_Rotation(const v8::FunctionCallbackInfo<v8::Value>& info);

class MYCLASS {
 public:

  Point(D_TYPE1 *par1) : rotate(par1) { }

  D_TYPE1 *rotate;

  void run_script()
  {
    v8::V8::InitializeICUDefaultLocation(argv);
    v8::V8::InitializeExternalStartupData(argv);
    std::unique_ptr<v8::Platform> platform = 
v8::platform::NewDefaultPlatform();
    v8::V8::InitializePlatform(platform.get());
    v8::V8::Initialize();

    v8::Isolate::CreateParams create_params;
    create_params.array_buffer_allocator = 
v8::ArrayBuffer::Allocator::NewDefaultAllocator();
    v8::Isolate* isolate = v8::Isolate::New(create_params);
    v8::Isolate::Scope isolate_scope(isolate);

v8::Isolate::Scope isolate_scope(isolate);

// Create a stack-allocated handle scope.
v8::HandleScope handle_scope(isolate);

// Create a template for the global object.
v8::Handle<v8::ObjectTemplate> global = v8::ObjectTemplate::New(isolate);

/* Here the internal field count is set to 1 which means the object has one 
internal field, with an index of 0, that points to a C++ object.*/
global->SetInternalFieldCount(1);

// Bind the 'update_rotation' function
global->Set(v8::String::NewFromUtf8(isolate, "update_rotation", 
v8::NewStringType::kNormal).ToLocalChecked(),
v8::FunctionTemplate::New(isolate, Update_Rotation)); 
// Create a new context.
v8::Local<v8::Context> context = v8::Context::New(isolate, NULL, global);
//Persistent<Context> context = v8::Context::New(isolate, NULL, global, 
nullptr);

// Enter the context for compiling and running the script.
v8::Context::Scope context_scope(context);

Local<Object> obj = global->NewInstance(context).ToLocalChecked();
obj->SetInternalField(0, External::New(isolate, this)); 
/* My JS script */
v8::Local<v8::String> source = v8::String::NewFromUtf8(isolate, "var 
rotate_status = 
update_rotation();",v8::NewStringType::kNormal).ToLocalChecked();
//exception handler
v8::TryCatch try_catch(isolate);

printf("Script : compilation started\n");
// Compile the source code.
v8::Local<v8::Script> script = v8::Script::Compile(context, 
source).ToLocalChecked();
printf("Script : compilation compilation done\n");
printf("Script : Running started\n");
// Run the script to get the result.
v8::Local<v8::Value> result = script->Run(context).ToLocalChecked(); 
  }
};

void Update_Rotation(const v8::FunctionCallbackInfo<v8::Value>& info) {
Local<Object> self = info.Holder();
Local<External> wrap = Local<External>::Cast(self->GetInternalField(0));
void* ptr = wrap->Value();
*MYCLASS* temp_sp = static_cast<MYCLASS*>(ptr);                          
 //--> Here i am always getting null pointer*
D_TYPE1 *rotate_ptr = static_cast<Point*>(ptr)->rotate;

    rotate_ptr->Update();
}


int main()
{
    D_TYPE1 *sample_rotate_obj = new D_TYPE1();
    MYCLASS test_obj(sample_rotate_obj);

    test_obj.run_script();
}


Can anyone plz suggest how to fix it to get valid pointer to my object?

Thanks in advance ...

Regards
Sudheer

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