64 lines
1.8 KiB
C
64 lines
1.8 KiB
C
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/*
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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#pragma once
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#include <functional>
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#include <memory>
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#include <mutex>
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#include <shared_mutex>
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namespace facebook::react {
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/*
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* `SharedFunction` implements a pattern of a shared callable object that
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* contains the same executable inside. It's similar to `std::function` with
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* one important difference: when the object is copied, the stored function (and
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* captured values) are shared between instances (not copied). `SharedFunction`
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* can be stored inside `std::function` because it's callable. It useful in some
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* scenarios, such as:
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* - When captured by `std::function` arguments are not copyable;
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* - When we need to replace the content of the callable later on the go.
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*/
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template <typename... ArgumentT>
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class SharedFunction {
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using T = void(ArgumentT...);
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struct Pair {
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Pair(std::function<T>&& function) : function(std::move(function)) {}
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std::function<T> function;
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std::shared_mutex mutex{};
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};
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public:
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SharedFunction(std::function<T>&& function = nullptr)
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: pair_(std::make_shared<Pair>(std::move(function))) {}
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SharedFunction(const SharedFunction& other) = default;
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SharedFunction(SharedFunction&& other) noexcept = default;
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SharedFunction& operator=(const SharedFunction& other) = default;
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SharedFunction& operator=(SharedFunction&& other) noexcept = default;
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void assign(std::function<T> function) const {
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std::unique_lock lock(pair_->mutex);
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pair_->function = function;
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}
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void operator()(ArgumentT... args) const {
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std::shared_lock lock(pair_->mutex);
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if (pair_->function) {
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pair_->function(args...);
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}
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}
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private:
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std::shared_ptr<Pair> pair_;
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};
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} // namespace facebook::react
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