133 lines
4.0 KiB
C++
133 lines
4.0 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 <atomic>
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#include <cstddef>
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#include <functional>
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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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#include <folly/Likely.h>
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#include <folly/Synchronized.h>
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#include <folly/io/async/EventBase.h>
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#include <folly/lang/Thunk.h>
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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() = default;
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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, void* ptr, void (*dtor)(void*));
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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.emplace(evb, Foo(1, 2));
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* myFoo.emplace(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.try_emplace(evb, 1, 2); // ctor if missing
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* Foo& foo = myFoo.try_emplace(evb, 1, 2); // noop if present
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* myFoo.erase(evb);
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* Foo& foo = myFoo.try_emplace_with(evb, [] { return 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 emplace/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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private:
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template <typename U, typename... A>
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using if_ilist_emplaceable_t = std::enable_if_t<
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std::is_constructible<T, std::initializer_list<U>, A...>::value,
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int>;
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T& store(EventBase& evb, T* const ptr) {
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setVoid(evb, ptr, detail::thunk::ruin<T>);
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return *ptr;
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}
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public:
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EventBaseLocal() = default;
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T* get(EventBase& evb) { return static_cast<T*>(getVoid(evb)); }
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template <typename... A>
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T& emplace(EventBase& evb, A&&... a) {
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return store(evb, new T(static_cast<A&&>(a)...));
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}
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template <typename U, typename... A, if_ilist_emplaceable_t<U, A...> = 0>
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T& emplace(EventBase& evb, std::initializer_list<U> i, A&&... a) {
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return store(evb, new T(i, static_cast<A&&>(a)...));
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}
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template <typename F>
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T& emplace_with(EventBase& evb, F f) {
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return store(evb, new T(f()));
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}
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template <typename... A>
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T& try_emplace(EventBase& evb, A&&... a) {
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auto const ptr = get(evb);
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return FOLLY_LIKELY(!!ptr) ? *ptr : emplace(evb, static_cast<A&&>(a)...);
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}
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template <typename U, typename... A, if_ilist_emplaceable_t<U, A...> = 0>
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T& try_emplace(EventBase& evb, std::initializer_list<U> i, A&&... a) {
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auto const ptr = get(evb);
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return FOLLY_LIKELY(!!ptr) ? *ptr : emplace(evb, i, static_cast<A&&>(a)...);
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}
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template <typename F>
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T& try_emplace_with(EventBase& evb, F f) {
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auto const ptr = get(evb);
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return FOLLY_LIKELY(!!ptr) ? *ptr : emplace_with(evb, std::ref(f));
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}
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};
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} // namespace folly
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