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#pragma once
#include <mbgl/util/optional.hpp>
#include <future>
#include <utility>
namespace mbgl {
// A movable type-erasing function wrapper. This allows to store arbitrary invokable
// things (like std::function<>, or the result of a movable-only std::bind()) in the queue.
// Source: http://stackoverflow.com/a/29642072/331379
class Message {
public:
virtual ~Message() = default;
virtual void operator()() = 0;
};
template <class Object, class MemberFn, class ArgsTuple>
class MessageImpl : public Message {
public:
MessageImpl(Object& object_, MemberFn memberFn_, ArgsTuple argsTuple_)
: object(object_),
memberFn(memberFn_),
argsTuple(std::move(argsTuple_)) {
}
void operator()() override {
invoke(std::make_index_sequence<std::tuple_size<ArgsTuple>::value>());
}
template <std::size_t... I>
void invoke(std::index_sequence<I...>) {
(object.*memberFn)(std::move(std::get<I>(argsTuple))...);
}
Object& object;
MemberFn memberFn;
ArgsTuple argsTuple;
};
template <class ResultType, class Object, class MemberFn, class ArgsTuple>
class AskMessageImpl : public Message {
public:
AskMessageImpl(std::promise<ResultType> promise_, Object& object_, MemberFn memberFn_, ArgsTuple argsTuple_)
: object(object_),
memberFn(memberFn_),
argsTuple(std::move(argsTuple_)),
promise(std::move(promise_)) {
}
void operator()() override {
promise.set_value(ask(std::make_index_sequence<std::tuple_size<ArgsTuple>::value>()));
}
template <std::size_t... I>
ResultType ask(std::index_sequence<I...>) {
return (object.*memberFn)(std::move(std::get<I>(argsTuple))...);
}
Object& object;
MemberFn memberFn;
ArgsTuple argsTuple;
std::promise<ResultType> promise;
};
namespace actor {
template <class Object, class MemberFn, class... Args>
std::unique_ptr<Message> makeMessage(Object& object, MemberFn memberFn, Args&&... args) {
auto tuple = std::make_tuple(std::forward<Args>(args)...);
return std::make_unique<MessageImpl<Object, MemberFn, decltype(tuple)>>(object, memberFn, std::move(tuple));
}
template <class ResultType, class Object, class MemberFn, class... Args>
std::unique_ptr<Message> makeMessage(std::promise<ResultType>&& promise, Object& object, MemberFn memberFn, Args&&... args) {
auto tuple = std::make_tuple(std::forward<Args>(args)...);
return std::make_unique<AskMessageImpl<ResultType, Object, MemberFn, decltype(tuple)>>(std::move(promise), object, memberFn, std::move(tuple));
}
} // namespace actor
} // namespace mbgl
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