60 lines
1.8 KiB
C++
60 lines
1.8 KiB
C++
#pragma once
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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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template <class Object>
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class EstablishedActor;
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template <class Object>
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class Actor;
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/**
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An `AspiringActor<O>` is one half of the pair of types that comprise an
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actor (see `Actor<O>`), the other half being `EstablishedActor<O>`. It is
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responsible for:
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- ownership of the actor's `Mailbox`
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- allocating the memory for (but *not* constructing) the target object `O`
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Using these two pieces--the mailbox and a stable address for `O`--an
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`AspiringActor<O>` can accept messages for the target object, or provide
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`ActorRef<O>`s that do so, before the object has actually been constructed by
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the corresponding `EstablishedActor<O>`. (Such messages are queued in the
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mailbox until after the object is constructed.)
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This allows for an `AspiringActor<O>` to be created and safely used by a
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thread other than the one on which the target object will (eventually) live.
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*/
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template <class Object>
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class AspiringActor {
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public:
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AspiringActor()
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: mailbox(std::make_shared<Mailbox>()) {
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// mailbox starts closed because the `Object` hasn't yet been constructed
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assert(!mailbox->isOpen());
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}
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AspiringActor(const AspiringActor&) = delete;
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ActorRef<std::decay_t<Object>> self() { return ActorRef<std::decay_t<Object>>(object(), mailbox); }
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private:
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std::shared_ptr<Mailbox> mailbox;
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std::aligned_storage_t<sizeof(Object)> objectStorage;
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Object& object() { return reinterpret_cast<Object&>(objectStorage); }
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friend class EstablishedActor<Object>;
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friend class Actor<Object>;
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};
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} // namespace mbgl
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