Repository navigation
Avoid extra memory allocation with templates #602
Description
I suppose that it is possible to add methods in the following way to avoid extra memory allocation:
Example:
template <class T>
class ObjectWrap {
using MethodType = Value (T::*)(const CallbackInfo &info);
template <MethodType method>
static auto ObjectWrap<T>::InstanceMethod2(const char* utf8name) -> ClassPropertyDescriptor<T>;
};
template <typename T>
template <typename ObjectWrap<T>::MethodType method>
inline auto ObjectWrap<T>::InstanceMethod2(const char* utf8name) -> ClassPropertyDescriptor<T> {
napi_property_descriptor desc = {};
desc.utf8name = utf8name;
desc.method = [](napi_evn env, napi_callback_info args) {
return details:;WrapCallback([&]{
CallbackInfo cb_info(env, args);
T* instance = Unwrap(cb_info.This().As<Object>());
return (instance->*cb)(callbackInfo);
});
};
return desc;
}
// How to use
class Test: public Napi::ObjectWrap<Test> {
public:
static auto define_class(Napi::Env env) -> Napi::Function {
return DefineClass(env, "Test", {
InstanceMethod2<&Test::get_value>("get_value");
});
}
auto get_value(const Napi::CallbackInfo &args) -> Napi::Value;
};
Activity
gabrielschulhof commentedon Nov 17, 2019
This does indeed work, and avoiding a memory allocation is definitely worth it. I'm not sure how to incorporate this, though. We should probably phase out the existing instance methods and accessors.
dmitryash commentedon Nov 18, 2019
Let me take it
gabrielschulhof commentedon Nov 18, 2019
@dmitryash we discussed this during today's team meeting. The best approach is to add an alternate set of methods to
ObjectWrap<T>and encourage their use over the existing methods. We can deprecate the existing methods and eventually remove them. Not sure what the name should be though –InstanceMethod2()does not seem too expressive. OTOHTemplatedInstanceMethod()is way too long of a name. I dunno ...InstanceMethodT()🤷 😕gabrielschulhof commentedon Nov 18, 2019
@dmitryash so if you would like to do a PR, then please, go right ahead 🙂
objectwrap: add template methods
objectwrap: add template methods
objectwrap: add template methods
objectwrap: add template methods