You can use a combination of SWIG and Napi. An existing repo which does this is available here, with a blog here. But I'll sum up the process here.
Create your class to use in SWIG, which has a thread running in the threadMain method :
#include <Thread.H>
class Test : public ThreadedMethod {
void *threadMain(void);
public:
Test();
void setFnPointer(const char* s);
};
Now in the Napi code, you will generate your thread safe function like so :
Napi::ThreadSafeFunction tsfn; ///< The node api's threadsafe function
Napi::Value Start( const Napi::CallbackInfo& info ){
Napi::Env env = info.Env();
// Create a ThreadSafeFunction
tsfn = Napi::ThreadSafeFunction::New(env,
info[0].As<Napi::Function>(), // JavaScript function to call
"Resource Name", 0,1);
// return the tsfn as a pointer in a string
char addr[24];
sprintf(addr,"%p",&tsfn);
return Napi::String::New(env, addr);
}
// some small code to call NODE_API_MODULE here, check the file NapiCode.C in the repo
You compile the SWIG code to one module and the Napi code down to a different module and you pass the thread safe funciton pointer from one to the other like so :
var libNapiNodejs = require('../swig/.libs/libNapiNodejs');
let fp = libNapiNodejs.start(function () {
console.log("JavaScript callback called with arguments", Array.from(arguments));
}, 5);
// SWIG get our C++ and thread running
var libSwigCNodejs = require('../swig/.libs/libSwigCNodejs');
let test = new libSwigCNodejs.Test;
test.setFnPointer(fp); // tell swig the callback function pointer to execute
test.run(); // run the C++ thread in the SWIG module
You will see that the C++ thread calls the javascript function. This is what the C++ thread looks like in SWIG :
Napi::ThreadSafeFunction *tsfn; ///< The node api's threadsafe function
void *Test::threadMain(void){
printf("C++ Thread enter %s\n",__func__);
auto callback = []( Napi::Env env, Napi::Function jsCallback, int* value ) {
jsCallback.Call( {Napi::Number::New( env, *value )} );
};
for (int i=0; i<10; i++){
sleep(1);
if (*tsfn) {
printf("calling tsfn->BlockingCall\n");
napi_status status = tsfn->BlockingCall( &i, callback );
if ( status != napi_ok ) // Handle error
break;
}
}
tsfn->Release();
printf("C++ Thread exit %s\n",__func__);
return NULL;
}
