Node.js C++: Asynchronous Event Notification with uv_async_init

uv_async_init is a function provided by the libuv library which is used to create an asynchronous event notification mechanism for a given event loop. This function is used to initialize an uv_async_t handle which can be used to send asynchronous notifications from a C++ thread to the main event loop thread in a Node.js application.

uv_async_init takes two arguments:

1. loop: A pointer to the event loop on which the async handle will be registered.
2. async: A pointer to an uv_async_t handle which will be initialized by the function.

Here is an example of using uv_async_init in a C++ addon for Node.js:

#include <node.h>
#include <uv.h>

static uv_async_t async;

void async_callback(uv_async_t* handle) {
  // This callback function will be called on the main event loop thread
  // when an async notification is received.
}

void async_send() {
  // This function can be called from any thread to send an async notification
  // to the main event loop thread.
  uv_async_send(&async);
}

void Init(v8::Local<v8::Object> exports) {
  uv_async_init(uv_default_loop(), &async, async_callback);
  exports->Set(Nan::New("async_send").ToLocalChecked(),
               Nan::New<v8::FunctionTemplate>(async_send)->GetFunction());
}

NODE_MODULE(addon, Init)

In this example, the uv_async_t handle is initialized in the Init function and a callback function async_callback is registered to be called when an async notification is received. A function async_send is also provided which can be called from any thread to send an async notification to the main event loop thread.

Note that the uv_default_loop() function is used to obtain a pointer to the default event loop for the Node.js application. If you are using a custom event loop, you will need to pass a pointer to that event loop instead.