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