节点.js C++插件:线程

答案是，你通常希望通过将你的工作提交到 uv 事件队列来使用 Nodejs 管理的后台线程，然后让 nodejs 担心如何创建和管理线程。

下面是节点.js v0.10 手册中缺少的样板示例。

struct Baton
{
    // we need this structure to interact with the uv
    // the uv_work_t must be the initial element and should store 
    // the callback function to be useful, but the rest
    // is user defined depending on what is needed to actually do the work.
    uv_work_t                    request;
    v8::Persistent<v8::Function> callback;
    // Add more elements to the structure as needed
    int                          countdown;
};

static void AsyncTestWork (uv_work_t* req);
static void AsyncTestAfter(uv_work_t* req,int status);
static Handle<Value> AsyncTestPrep(const Arguments& args) 
{
    HandleScope scope;
    if (args.Length() != 1) {
        ThrowException(Exception::TypeError(String::New("Wrong number of arguments -- needs (callback)")));
        return scope.Close(Undefined());
    }
    if (!args[0]->IsFunction()) {
        ThrowException(Exception::TypeError(String::New("Wrong type of arguments -- needs (callback)")));
        return scope.Close(Undefined());
    }
    v8::Local<v8::Function> callback = v8::Local<v8::Function>::Cast(args[0]);
    Baton* baton = new Baton();
    baton->request.data = baton;
    baton->callback = v8::Persistent<v8::Function>::New(callback);
    baton->countdown = 3;
    uv_queue_work(uv_default_loop(), &baton->request, AsyncTestWork, AsyncTestAfter);
    return scope.Close(v8::Undefined());
}

static void AsyncTestWork (uv_work_t* req)
{
    // This method will run in a seperate thread where you can do 
    // your blocking background work.
    // In this function, you cannot under any circumstances access any V8/node js
    // valiables -- all data and memory needed, MUSt be in the Baton structure
    Baton* baton = static_cast<Baton*>(req->data);
    sleep(6); // some fictional work, delaying the return....
    baton->countdown -= 1;  // my actual work in this 
}
static void AsyncTestAfter(uv_work_t* req,int status)
{
    // This is what is called after the 'Work' is done, you can now move any data from 
    // Baton to the V8/Nodejs space and invoke call back functions
    Baton* baton = static_cast<Baton*>(req->data);
    v8::Handle<v8::Value> argv1[] = { v8::Null(), Number::New(baton->countdown) };
    v8::Handle<v8::Value> argv2[] = { v8::Null(), Number::New(23) };
    v8::TryCatch try_catch;
       // Call back to the JS function, you can make as many/few callbacks  
       // as you need, they just go on the event loop queue for now.
       // Note: that it is mostly customary to call the callback  
       // function just (exactly) which is probably what you want  
       // to do to avoid confusing your users if you make a public api
       baton->callback->Call(v8::Context::GetCurrent()->Global(), 2, argv1);
       baton->callback->Call(v8::Context::GetCurrent()->Global(), 2, argv2);
    if (try_catch.HasCaught()) {
        node::FatalException(try_catch);
    }
    if (baton->countdown > 0) {
        // resubmit the worker for yet more work
        uv_queue_work(uv_default_loop(), &baton->request, AsyncTestWork, AsyncTestAfter);
    } else {
        // we are finished, clean up and be done
        baton->callback.Dispose();
        delete baton;
    }
}

void init(Handle<Object> exports) 
{
  exports->Set(String::NewSymbol("myAsyncTestFunction"),
               FunctionTemplate::New(AsyncTestPrep)->GetFunction());
}