{

void lock()

{

std::thread::id defaultId;

const std::thread::id currentThreadId = std::this_thread::get_id();

if (m_ownerThreadId.compare_exchange_strong(defaultId, currentThreadId))

{

const uint32_t oldValue = m_count.fetch_add(1);

if (oldValue == 0)

{

std::mutex::lock();

}

}

else if (defaultId != currentThreadId)

{

std::mutex::lock(); // lock and wait for the other thread that owns the mutex

m_ownerThreadId = currentThreadId;

m_count = 1;

}

else

{

// defaultId == currentThreadId: reentry of mutex owner thread

m_count++;

}

}

void unlock()

{

const uint32_t oldValue = m_count.fetch_sub(1);

if (oldValue == 1)

{

m_ownerThreadId = std::thread::id{};

std::mutex::unlock();

}

}

std::atomic<std::thread::id> m_ownerThreadId{}; // a default-constructed thread id is treated as an invalid thread id

std::atomic<uint32_t> m_count{0};