121 lines
3.6 KiB
C++
121 lines
3.6 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <folly/Synchronized.h>
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#include <folly/io/async/EventBase.h>
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#include <memory>
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#include <mutex>
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#include <unordered_set>
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#include <utility>
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namespace folly {
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namespace detail {
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class EventBaseLocalBase : public EventBaseLocalBaseBase {
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public:
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EventBaseLocalBase() {}
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EventBaseLocalBase(const EventBaseLocalBase&) = delete;
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EventBaseLocalBase& operator=(const EventBaseLocalBase&) = delete;
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~EventBaseLocalBase() override;
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void erase(EventBase& evb);
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void onEventBaseDestruction(EventBase& evb) override;
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protected:
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void setVoid(EventBase& evb, std::shared_ptr<void>&& ptr);
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void* getVoid(EventBase& evb);
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folly::Synchronized<std::unordered_set<EventBase*>> eventBases_;
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static std::atomic<std::size_t> keyCounter_;
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std::size_t key_{keyCounter_++};
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};
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} // namespace detail
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/**
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* A storage abstraction for data that should be tied to an EventBase.
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*
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* struct Foo { Foo(int a, int b); };
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* EventBaseLocal<Foo> myFoo;
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* ...
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* EventBase evb;
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* myFoo.set(evb, new Foo(1, 2));
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* myFoo.set(evb, 1, 2);
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* Foo* foo = myFoo.get(evb);
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* myFoo.erase(evb);
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* Foo& foo = myFoo.getOrCreate(evb, 1, 2); // ctor
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* Foo& foo = myFoo.getOrCreate(evb, 1, 2); // no ctor
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* myFoo.erase(evb);
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* Foo& foo = myFoo.getOrCreateFn(evb, [] () { return new Foo(3, 4); })
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*
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* The objects will be deleted when the EventBaseLocal or the EventBase is
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* destructed (whichever comes first). All methods must be called from the
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* EventBase thread.
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*
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* The user is responsible for throwing away invalid references/ptrs returned
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* by the get() method after set/erase is called. If shared ownership is
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* needed, use a EventBaseLocal<shared_ptr<...>>.
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*/
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template <typename T>
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class EventBaseLocal : public detail::EventBaseLocalBase {
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public:
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EventBaseLocal() : EventBaseLocalBase() {}
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T* get(EventBase& evb) {
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return static_cast<T*>(getVoid(evb));
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}
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void emplace(EventBase& evb, T* ptr) {
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std::shared_ptr<T> smartPtr(ptr);
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setVoid(evb, std::move(smartPtr));
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}
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template <typename... Args>
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void emplace(EventBase& evb, Args&&... args) {
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auto smartPtr = std::make_shared<T>(std::forward<Args>(args)...);
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setVoid(evb, smartPtr);
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}
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template <typename... Args>
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T& getOrCreate(EventBase& evb, Args&&... args) {
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if (auto ptr = getVoid(evb)) {
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return *static_cast<T*>(ptr);
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}
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auto smartPtr = std::make_shared<T>(std::forward<Args>(args)...);
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auto& ref = *smartPtr;
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setVoid(evb, std::move(smartPtr));
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return ref;
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}
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template <typename Func>
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T& getOrCreateFn(EventBase& evb, Func fn) {
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// If this looks like it's copy/pasted from above, that's because it is.
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// gcc has a bug (fixed in 4.9) that doesn't allow capturing variadic
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// params in a lambda.
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if (auto ptr = getVoid(evb)) {
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return *static_cast<T*>(ptr);
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}
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std::shared_ptr<T> smartPtr(fn());
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auto& ref = *smartPtr;
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setVoid(evb, std::move(smartPtr));
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return ref;
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}
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};
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} // namespace folly
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