| 1 | #pragma once |
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| 2 | |
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| 3 | #include <mbgl/actor/mailbox.hpp> |
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| 4 | #include <mbgl/actor/message.hpp> |
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| 5 | #include <mbgl/actor/actor_ref.hpp> |
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| 6 | |
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| 7 | #include <memory> |
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| 8 | #include <future> |
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| 9 | #include <type_traits> |
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| 10 | #include <cassert> |
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| 11 | |
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| 12 | namespace mbgl { |
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| 13 | |
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| 14 | template <class Object> |
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| 15 | class EstablishedActor; |
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| 16 | |
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| 17 | template <class Object> |
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| 18 | class Actor; |
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| 19 | |
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| 20 | /* |
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| 21 | An `AspiringActor<O>` is one half of the pair of types that comprise an actor (see `Actor<O>`), |
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| 22 | the other half being `EstablishedActor<O>`. It is responsible for: |
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| 23 | - ownership of the actor's `Mailbox` |
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| 24 | - allocating the memory for (but *not* constructing) the target object `O` |
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| 25 | |
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| 26 | Using these two pieces--the mailbox and a stable address for `O`--an `AspiringActor<O>` can |
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| 27 | accept messages for the target object, or provide `ActorRef<O>`s that do so, before the object |
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| 28 | has actually been constructed by the corresponding `EstablishedActor<O>`. (Such messages are |
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| 29 | queued in the mailbox until after the object is constructed.) |
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| 30 | |
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| 31 | This allows for an `AspiringActor<O>` to be created and safely used by a thread other than the |
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| 32 | one on which the target object will (eventually) live. |
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| 33 | */ |
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| 34 | template <class Object> |
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| 35 | class AspiringActor { |
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| 36 | public: |
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| 37 | AspiringActor() : mailbox(std::make_shared<Mailbox>()) { |
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| 38 | // mailbox starts closed because the `Object` hasn't yet been constructed |
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| 39 | assert(!mailbox->isOpen()); |
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| 40 | } |
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| 41 | |
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| 42 | AspiringActor(const AspiringActor&) = delete; |
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| 43 | |
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| 44 | ActorRef<std::decay_t<Object>> self() { |
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| 45 | return ActorRef<std::decay_t<Object>>(object(), mailbox); |
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| 46 | } |
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| 47 | |
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| 48 | private: |
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| 49 | std::shared_ptr<Mailbox> mailbox; |
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| 50 | std::aligned_storage_t<sizeof(Object)> objectStorage; |
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| 51 | |
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| 52 | Object& object() { |
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| 53 | return *reinterpret_cast<Object *>(&objectStorage); |
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| 54 | } |
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| 55 | |
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| 56 | friend class EstablishedActor<Object>; |
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| 57 | friend class Actor<Object>; |
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| 58 | }; |
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| 59 | |
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| 60 | } // namespace mbgl |
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| 61 | |
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