global.hpp

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#pragma once
 
 
#include <prom/adapter.hpp>
#include <prom/null_adapter.hpp>
 
#include <atomic>
#include <cstdint>
#include <memory>
#include <mutex>
#include <utility>
 
namespace prom {
 
class AdapterCell final : public AdapterSource {
public:
    AdapterCell() : adapter_(std::make_shared<NullAdapter>()) {}
 
    explicit AdapterCell(AdapterPtr adapter)
        : adapter_(adapter ? std::move(adapter) : std::make_shared<NullAdapter>()) {}
 
    [[nodiscard]] std::uint64_t version() const noexcept override {
        return version_.load(std::memory_order_acquire);
    }
 
    [[nodiscard]] AdapterPtr adapter() const override {
        const std::scoped_lock lock(mutex_);
        return adapter_;
    }
 
    void set_adapter(AdapterPtr adapter) {
        {
            const std::scoped_lock lock(mutex_);
            adapter_ = adapter ? std::move(adapter) : std::make_shared<NullAdapter>();
        }
        version_.fetch_add(1, std::memory_order_release);
    }
 
private:
    mutable std::mutex mutex_;
    AdapterPtr adapter_;
    std::atomic<std::uint64_t> version_{0};
};
 
namespace detail {
 
[[nodiscard]] inline std::shared_ptr<AdapterCell> global_adapter_cell() {
    static auto cell = std::make_shared<AdapterCell>();
    return cell;
}
 
}  // namespace detail
 
}  // namespace prom