CallbackGate.hpp

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#ifndef DPDKLIBS_INCLUDE_DPDKLIBS_SENDER_CALLBACKGATE_HPP_
#define DPDKLIBS_INCLUDE_DPDKLIBS_SENDER_CALLBACKGATE_HPP_
 
#include <mutex>
#include <shared_mutex>
#include <utility>
 
namespace dunedaq::dpdklibs::sender {
 
template<typename Owner>
class CallbackGate
{
public:
  CallbackGate() = default;
  CallbackGate(const CallbackGate&) = delete;
  CallbackGate& operator=(const CallbackGate&) = delete;
  CallbackGate(CallbackGate&&) = delete;
  CallbackGate& operator=(CallbackGate&&) = delete;
 
  void arm(Owner* owner)
  {
    std::unique_lock lock(m_mutex);
    m_owner = owner;
  }
 
  // Blocks until every in-flight dispatch() has returned, then disarms.
  void tombstone()
  {
    std::unique_lock lock(m_mutex);
    m_owner = nullptr;
  }
 
  bool armed() const
  {
    std::shared_lock lock(m_mutex);
    return m_owner != nullptr;
  }
 
  // Invoke fn(*owner) under a shared lock if armed.  Returns true if fn ran.
  // The shared lock guarantees the owner outlives the call with respect to
  // tombstone().  It does not serialize concurrent dispatches.
  template<typename Fn>
  bool dispatch(Fn&& fn)
  {
    std::shared_lock lock(m_mutex);
    if (m_owner == nullptr) {
      return false;
    }
    std::forward<Fn>(fn)(*m_owner);
    return true;
  }
 
private:
  mutable std::shared_mutex m_mutex;
  Owner* m_owner = nullptr;
};
 
} // namespace dunedaq::dpdklibs::sender
 
#endif // DPDKLIBS_INCLUDE_DPDKLIBS_SENDER_CALLBACKGATE_HPP_