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#pragma once
#include <mutex>
#include <c10/util/C++17.h>
namespace c10 {
/**
* A very simple Synchronization class for error-free use of data
* in a multi-threaded context. See folly/docs/Synchronized.md for
* the inspiration of this class.
*
* Full URL:
* https://github.com/facebook/folly/blob/main/folly/docs/Synchronized.md
*
* This class implements a small subset of the generic functionality
* implemented by folly:Synchronized<T>. Specifically, only withLock<T>
* is implemeted here since it's the smallest possible API that is
* able to cover a large surface area of functionality offered by
* folly::Synchronized<T>.
*/
template <typename T>
class Synchronized final {
mutable std::mutex mutex_;
T data_;
public:
Synchronized() = default;
Synchronized(T const& data) : data_(data) {}
Synchronized(T&& data) : data_(data) {}
// Don't permit copy construction, move, assignment, or
// move assignment, since the underlying std::mutex
// isn't necessarily copyable/moveable.
Synchronized(Synchronized const&) = delete;
Synchronized(Synchronized&&) = delete;
Synchronized operator=(Synchronized const&) = delete;
Synchronized operator=(Synchronized&&) = delete;
/**
* To use, call withLock<T> with a callback that accepts T either
* by copy or by reference. Use the protected variable in the
* provided callback safely.
*/
template <typename CB>
typename c10::invoke_result_t<CB, T&> withLock(CB cb) {
std::lock_guard<std::mutex> guard(this->mutex_);
return cb(this->data_);
}
/**
* To use, call withLock<T> with a callback that accepts T either
* by copy or by const reference. Use the protected variable in
* the provided callback safely.
*/
template <typename CB>
typename c10::invoke_result_t<CB, T const&> withLock(CB cb) const {
std::lock_guard<std::mutex> guard(this->mutex_);
return cb(this->data_);
}
};
} // end namespace c10
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