#ifndef RTORRENT_UTILS_WAITPID_QUEUE_H#define RTORRENT_UTILS_WAITPID_QUEUE_H #include <future>#include <set>#include <torrent/system/common.h> namespace utils { class WaitpidQueue {public:  WaitpidQueue();  ~WaitpidQueue();   uint32_t            size() const;   void                close_pid(int pid);   void                wait_for(uint32_t max_remaining);   // TODO: Add a signal handler to tell the worker thread to wake up. Use a counter to batch wakeups. private:  WaitpidQueue(const WaitpidQueue&) = delete;  WaitpidQueue& operator=(const WaitpidQueue&) = delete;   std::future<void>   m_worker;   align_cacheline   std::mutex          m_mutex;  std::set<pid_t>     m_queue;   align_cacheline   std::atomic<bool>     m_wakeup_worker{};  std::atomic<bool>     m_should_shutdown{};   std::atomic<uint32_t> m_remaining{};}; inline uint32_t WaitpidQueue::size() const { return m_remaining.load(std::memory_order_acquire); } } // namespace utils #endif