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include/asio/detail/service_registry.hpp

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+//
+// detail/service_registry.hpp
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2025 Christopher M. Kohlhoff (chris at kohlhoff dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+
+#ifndef ASIO_DETAIL_SERVICE_REGISTRY_HPP
+#define ASIO_DETAIL_SERVICE_REGISTRY_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include "asio/detail/config.hpp"
+#include <typeinfo>
+#include "asio/detail/mutex.hpp"
+#include "asio/detail/noncopyable.hpp"
+#include "asio/detail/type_traits.hpp"
+#include "asio/execution_context.hpp"
+
+#include "asio/detail/push_options.hpp"
+
+namespace asio {
+
+class io_context;
+
+namespace detail {
+
+template <typename T>
+class typeid_wrapper {};
+
+class service_registry
+  : private noncopyable
+{
+public:
+  // Constructor.
+  ASIO_DECL service_registry(execution_context& owner);
+
+  // Destructor.
+  ASIO_DECL ~service_registry();
+
+  // Shutdown all services.
+  ASIO_DECL void shutdown_services();
+
+  // Destroy all services.
+  ASIO_DECL void destroy_services();
+
+  // Notify all services of a fork event.
+  ASIO_DECL void notify_fork(execution_context::fork_event fork_ev);
+
+  // Get the service object corresponding to the specified service type. Will
+  // create a new service object automatically if no such object already
+  // exists. Ownership of the service object is not transferred to the caller.
+  template <typename Service>
+  Service& use_service();
+
+  // Get the service object corresponding to the specified service type. Will
+  // create a new service object automatically if no such object already
+  // exists. Ownership of the service object is not transferred to the caller.
+  // This overload is used for backwards compatibility with services that
+  // inherit from io_context::service.
+  template <typename Service>
+  Service& use_service(io_context& owner);
+
+  // Create and add a service object.
+  template <typename Service, typename... Args>
+  Service& make_service(Args&&... args);
+
+  // Add a service object. Throws on error, in which case ownership of the
+  // object is retained by the caller.
+  template <typename Service>
+  void add_service(Service* new_service);
+
+  // Check whether a service object of the specified type already exists.
+  template <typename Service>
+  bool has_service() const;
+
+private:
+  // Initialise a service's key when the key_type typedef is not available.
+  template <typename Service>
+  static void init_key(execution_context::service::key& key, ...);
+
+#if !defined(ASIO_NO_TYPEID)
+  // Initialise a service's key when the key_type typedef is available.
+  template <typename Service>
+  static void init_key(execution_context::service::key& key,
+      enable_if_t<is_base_of<typename Service::key_type, Service>::value>*);
+#endif // !defined(ASIO_NO_TYPEID)
+
+  // Initialise a service's key based on its id.
+  ASIO_DECL static void init_key_from_id(
+      execution_context::service::key& key,
+      const execution_context::id& id);
+
+#if !defined(ASIO_NO_TYPEID)
+  // Initialise a service's key based on its id.
+  template <typename Service>
+  static void init_key_from_id(execution_context::service::key& key,
+      const service_id<Service>& /*id*/);
+#endif // !defined(ASIO_NO_TYPEID)
+
+  // Check if a service matches the given id.
+  ASIO_DECL static bool keys_match(
+      const execution_context::service::key& key1,
+      const execution_context::service::key& key2);
+
+  // The type of a factory function used for creating a service instance.
+  typedef execution_context::service*(*factory_type)(execution_context&, void*);
+
+  // Factory function for creating a service instance.
+  template <typename Service, typename Owner, typename... Args>
+  static execution_context::service* create(
+      execution_context& context, void* owner, Args&&... args);
+
+  // Helper function to destroy an allocated service instance.
+  template <typename Service>
+  static void destroy_allocated(execution_context::service* service);
+
+  // Helper function to destroy an added service instance.
+  ASIO_DECL static void destroy_added(
+      execution_context::service* service);
+
+  // Helper class to manage service pointers.
+  struct auto_service_ptr;
+  friend struct auto_service_ptr;
+  struct auto_service_ptr
+  {
+    execution_context::service* ptr_;
+    ASIO_DECL ~auto_service_ptr();
+  };
+
+  // Get the service object corresponding to the specified service key. Will
+  // create a new service object automatically if no such object already
+  // exists. Ownership of the service object is not transferred to the caller.
+  ASIO_DECL execution_context::service* do_use_service(
+      const execution_context::service::key& key,
+      factory_type factory, void* owner);
+
+  // Add a service object. Throws on error, in which case ownership of the
+  // object is retained by the caller.
+  ASIO_DECL void do_add_service(
+      const execution_context::service::key& key,
+      execution_context::service* new_service);
+
+  // Check whether a service object with the specified key already exists.
+  ASIO_DECL bool do_has_service(
+      const execution_context::service::key& key) const;
+
+  // Mutex to protect access to internal data.
+  mutable asio::detail::mutex mutex_;
+
+  // The owner of this service registry and the services it contains.
+  execution_context& owner_;
+
+  // The first service in the list of contained services.
+  execution_context::service* first_service_;
+};
+
+} // namespace detail
+} // namespace asio
+
+#include "asio/detail/pop_options.hpp"
+
+#include "asio/detail/impl/service_registry.hpp"
+#if defined(ASIO_HEADER_ONLY)
+# include "asio/detail/impl/service_registry.ipp"
+#endif // defined(ASIO_HEADER_ONLY)
+
+#endif // ASIO_DETAIL_SERVICE_REGISTRY_HPP