service.hpp

#pragma once
 
#include <mutex>
#include <boost/asio/execution_context.hpp>
#include <boost/intrusive/list.hpp>
 
namespace nexus::quic::detail {
 
struct service_tag {};
using service_list_base_hook = boost::intrusive::list_base_hook<
    boost::intrusive::tag<service_tag>>;
 
template <typename IoObject>
class service : public boost::asio::execution_context::service {
  using base_hook = boost::intrusive::base_hook<service_list_base_hook>;
  boost::intrusive::list<IoObject, base_hook> entries;
  std::mutex mutex;
 
  void shutdown() override {
    while (!entries.empty()) {
      auto& entry = entries.front();
      entries.pop_front();
      entry.service_shutdown();
    }
  }
 public:
  using key_type = service;
  static inline boost::asio::execution_context::id id;
 
  explicit service(boost::asio::execution_context& ctx)
      : boost::asio::execution_context::service(ctx) {}
 
  void add(IoObject& entry) {
    auto lock = std::scoped_lock{mutex};
    entries.push_back(entry);
  }
  void remove(IoObject& entry) {
    auto lock = std::scoped_lock{mutex};
    if (entries.empty()) {
      // already shut down
    } else {
      entries.erase(entries.iterator_to(entry));
    }
  }
};
 
} // namespace nexus::quic::detail