33 Thread support library [thread]

33.4 Mutual exclusion [thread.mutex]

33.4.4 Locks [thread.lock]

33.4.4.4 Class template shared_­lock [thread.lock.shared]

namespace std {
  template <class Mutex>
  class shared_lock {
  public:
    using mutex_type = Mutex;

    // [thread.lock.shared.cons], construct/copy/destroy
    shared_lock() noexcept;
    explicit shared_lock(mutex_type& m);  // blocking
    shared_lock(mutex_type& m, defer_lock_t) noexcept;
    shared_lock(mutex_type& m, try_to_lock_t);
    shared_lock(mutex_type& m, adopt_lock_t);
    template <class Clock, class Duration>
      shared_lock(mutex_type& m,
                  const chrono::time_point<Clock, Duration>& abs_time);
    template <class Rep, class Period>
      shared_lock(mutex_type& m,
                const chrono::duration<Rep, Period>& rel_time);
    ~shared_lock();

    shared_lock(const shared_lock&) = delete;
    shared_lock& operator=(const shared_lock&) = delete;

    shared_lock(shared_lock&& u) noexcept;
    shared_lock& operator=(shared_lock&& u) noexcept;

    // [thread.lock.shared.locking], locking
    void lock();  // blocking
    bool try_lock();
    template <class Rep, class Period>
      bool try_lock_for(const chrono::duration<Rep, Period>& rel_time);
    template <class Clock, class Duration>
      bool try_lock_until(const chrono::time_point<Clock, Duration>& abs_time);
    void unlock();

    // [thread.lock.shared.mod], modifiers
    void swap(shared_lock& u) noexcept;
    mutex_type* release() noexcept;

    // [thread.lock.shared.obs], observers
    bool owns_lock() const noexcept;
    explicit operator bool () const noexcept;
    mutex_type* mutex() const noexcept;

  private:
    mutex_type* pm; // exposition only
    bool owns;      // exposition only
  };

  template<class Mutex> shared_lock(shared_lock<Mutex>) -> shared_lock<Mutex>;

  template <class Mutex>
    void swap(shared_lock<Mutex>& x, shared_lock<Mutex>& y) noexcept;
}