Slight modification of https://github.com/nikhilm/uvbook/blob/master/code/progress/main.c which uses uv_thread_create with nan

simple.cc

#include <nan.h>
#include <random>

#include <uv.h>

uv_loop_t *loop;
uv_async_t async;

using namespace v8;


struct Callbacks {
	NanCallback *onDeviceAddedCallback;
	NanCallback *onDeviceRemovedCallback;
};


struct RequestBaton {
	double percentage;
	NanCallback *onDeviceAdded;
	NanCallback *onDeviceRemoved;
};


void fake_download(void *arg) {

	//NanCallback *callback = (NanCallback*)arg;
	Callbacks *cbs = (Callbacks *)arg;
	

	//int size = req.size;
	int size = 10240;
	// init result baton
	int downloaded = 0;
	double percentage;

	while (downloaded < size) {
		percentage = downloaded*100.0 / size;
		RequestBaton rb = {
			percentage,
			cbs->onDeviceAddedCallback,
			cbs->onDeviceRemovedCallback
		};
		//req->percentage = percentage;

		async.data = (void *)&rb;
		uv_async_send(&async);

		Sleep(1000);
		downloaded += (200 + rand()) % 1000; // can only download max 1000bytes/sec,
		// but at least a 200;
	}

	// clearing from heap
	free(cbs);
}


void print_progress(uv_async_t *handle) {
	NanScope();
	//NanCallback *callback = (NanCallback *)handle->data;
	RequestBaton *rb = (struct RequestBaton *) handle->data;

	//fprintf(stderr, "Downloaded %.2f%%\n", percentage);
	Handle<Value> argv[] = {
		NanNew<Number>(rb->percentage)
	};
	rb->onDeviceAdded->Call(1, argv);
}


NAN_METHOD(DeviceDiscoverer) {

	uv_thread_t download_id;
	NanScope();

	Local<Function> fn1 = args[0].As<Function>();
	Local<Function> fn2 = args[1].As<Function>();
	NanCallback *deviceAddedCallback = new NanCallback(fn1);
	NanCallback *deviceRemovedCallback = new NanCallback(fn2);

	/*Handle<Value> argv[] = {
		NanNew<Number>(24.11)
	};*/

	//callback->Call(1, argv);
	loop = uv_default_loop();

	Callbacks *cb = (Callbacks *) malloc(sizeof(Callbacks));
	cb->onDeviceAddedCallback = deviceAddedCallback;
	cb->onDeviceRemovedCallback = deviceRemovedCallback; 

	uv_async_init(loop, &async, print_progress);
	uv_thread_create(&download_id, fake_download, (void *)cb);

	NanReturnUndefined();
}

NAN_METHOD(SayHello) {
	NanScope();

	NanReturnValue(NanNew<String>
		("No hello -- Booyakasha"));
}

void Init(Handle<Object> exports) {
	exports->Set(NanNew<String>("hello"), 
		NanNew<FunctionTemplate>(SayHello)->GetFunction());

	exports->Set(NanNew<String>("DeviceDiscoverer"),
		NanNew<FunctionTemplate>(DeviceDiscoverer)->GetFunction());
}



NODE_MODULE(simple, Init);