81 lines
3.3 KiB
C++
81 lines
3.3 KiB
C++
#pragma once
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#include <mbgl/actor/aspiring_actor.hpp>
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#include <mbgl/actor/mailbox.hpp>
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#include <mbgl/actor/message.hpp>
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#include <mbgl/actor/actor_ref.hpp>
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#include <memory>
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#include <future>
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#include <type_traits>
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#include <cassert>
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namespace mbgl {
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/*
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An `EstablishedActor<O>` is one half of the pair of types that comprise an actor (see `Actor<O>`),
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the other half being `AspiringActor<O>`. It is responsible for managing the lifetime of the
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target object `O` and the open/closed state of the parent's `mailbox`.
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The `O` object's lifetime is contained by that of its owning `EstablishedActor<O>`: the
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`EstablishedActor` constructor executes the `O` constructor via "placement new", constructing
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it at the address provided by the parent `AspiringActor`, and the `~EstablishedActor` destructor
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similarly executes the `~O` destructor (after closing the mailbox). `EstablishedActor` should
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therefore live entirely on the thread intended to own `O`.
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*/
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template <class Object>
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class EstablishedActor {
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public:
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// Construct the Object from a parameter pack `args` (i.e. `Object(args...)`)
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template <typename U = Object, class... Args, typename std::enable_if<
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std::is_constructible<U, Args...>::value ||
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std::is_constructible<U, ActorRef<U>, Args...>::value
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>::type * = nullptr>
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EstablishedActor(Scheduler& scheduler, AspiringActor<Object>& parent_, Args&& ... args)
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: parent(parent_) {
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emplaceObject(std::forward<Args>(args)...);
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parent.mailbox->open(scheduler);
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}
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// Construct the `Object` from a tuple containing the constructor arguments (i.e.
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// `Object(std::get<0>(args), std::get<1>(args), ...)`)
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template <class ArgsTuple, std::size_t ArgCount = std::tuple_size<std::decay_t<ArgsTuple>>::value>
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EstablishedActor(Scheduler& scheduler, AspiringActor<Object>& parent_, ArgsTuple&& args)
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: parent(parent_) {
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emplaceObject(std::forward<ArgsTuple>(args), std::make_index_sequence<ArgCount>{});
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parent.mailbox->open(scheduler);
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}
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EstablishedActor(const EstablishedActor&) = delete;
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~EstablishedActor() {
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parent.mailbox->close();
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parent.object().~Object();
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}
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private:
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// Enabled for Objects with a constructor taking ActorRef<Object> as the first parameter
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template <typename U = Object, class... Args, typename std::enable_if<std::is_constructible<U, ActorRef<U>, Args...>::value>::type * = nullptr>
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void emplaceObject(Args&&... args_) {
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new (&parent.objectStorage) Object(parent.self(), std::forward<Args>(args_)...);
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}
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// Enabled for plain Objects
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template <typename U = Object, class... Args, typename std::enable_if<std::is_constructible<U, Args...>::value>::type * = nullptr>
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void emplaceObject(Args&&... args_) {
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new (&parent.objectStorage) Object(std::forward<Args>(args_)...);
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}
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// Used to expand a tuple holding the constructor arguments
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template <class ArgsTuple, std::size_t... I>
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void emplaceObject(ArgsTuple&& args, std::index_sequence<I...>) {
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emplaceObject(std::move(std::get<I>(std::forward<ArgsTuple>(args)))...);
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(void) args; // mark args as used: if it's empty tuple, it's not actually used above.
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}
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AspiringActor<Object>& parent;
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};
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} // namespace mbgl
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