86 lines
2.5 KiB
C++
86 lines
2.5 KiB
C++
// 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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#pragma once
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#include <folly/Synchronized.h>
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#include <atomic>
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namespace yarpl {
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template <typename T>
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struct AtomicReference {
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folly::Synchronized<std::shared_ptr<T>, std::mutex> ref;
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AtomicReference() = default;
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AtomicReference(std::shared_ptr<T>&& r) {
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*(ref.lock()) = std::move(r);
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}
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};
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template <typename T>
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std::shared_ptr<T> atomic_load(AtomicReference<T>* ar) {
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return *(ar->ref.lock());
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}
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template <typename T>
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std::shared_ptr<T> atomic_exchange(
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AtomicReference<T>* ar,
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std::shared_ptr<T> r) {
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auto refptr = ar->ref.lock();
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auto old = std::move(*refptr);
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*refptr = std::move(r);
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return old;
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}
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template <typename T>
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std::shared_ptr<T> atomic_exchange(AtomicReference<T>* ar, std::nullptr_t) {
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return atomic_exchange(ar, std::shared_ptr<T>());
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}
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template <typename T>
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void atomic_store(AtomicReference<T>* ar, std::shared_ptr<T> r) {
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*ar->ref.lock() = std::move(r);
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}
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class enable_get_ref : public std::enable_shared_from_this<enable_get_ref> {
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private:
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virtual void dummy_internal_get_ref() {}
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protected:
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// materialize a reference to 'this', but a type even further derived from
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// Derived, because C++ doesn't have covariant return types on methods
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template <typename As>
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std::shared_ptr<As> ref_from_this(As* ptr) {
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// at runtime, ensure that the most derived class can indeed be
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// converted into an 'as'
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(void)ptr; // silence 'unused parameter' errors in Release builds
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return std::static_pointer_cast<As>(this->shared_from_this());
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}
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template <typename As>
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std::shared_ptr<As> ref_from_this(As const* ptr) const {
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// at runtime, ensure that the most derived class can indeed be
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// converted into an 'as'
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(void)ptr; // silence 'unused parameter' errors in Release builds
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return std::static_pointer_cast<As const>(this->shared_from_this());
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}
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public:
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virtual ~enable_get_ref() = default;
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};
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} /* namespace yarpl */
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