execution_context.hpp

//
// execution_context.hpp
// ~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2020 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_EXECUTION_CONTEXT_HPP
#define ASIO_EXECUTION_CONTEXT_HPP

#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)

#include "asio/detail/config.hpp"
#include <cstddef>
#include <stdexcept>
#include <typeinfo>
#include "asio/detail/noncopyable.hpp"
#include "asio/detail/variadic_templates.hpp"

#include "asio/detail/push_options.hpp"

namespace asio {

class execution_context;
class io_context;

#if !defined(GENERATING_DOCUMENTATION)
template <typename Service> Service& use_service(execution_context&);
template <typename Service> Service& use_service(io_context&);
template <typename Service> void add_service(execution_context&, Service*);
template <typename Service> bool has_service(execution_context&);
#endif // !defined(GENERATING_DOCUMENTATION)

namespace detail { class service_registry; }


class execution_context
  : private noncopyable
{
public:
  class id;
  class service;

public:
  ASIO_DECL execution_context();

  ASIO_DECL ~execution_context();

protected:

  ASIO_DECL void shutdown();


  ASIO_DECL void destroy();

public:
  enum fork_event
  {
    fork_prepare,

    fork_parent,

    fork_child
  };


  ASIO_DECL void notify_fork(fork_event event);


  template <typename Service>
  friend Service& use_service(execution_context& e);


  template <typename Service>
  friend Service& use_service(io_context& ioc);

#if defined(GENERATING_DOCUMENTATION)


  template <typename Service, typename... Args>
  friend Service& make_service(execution_context& e, Args&&... args);

#elif defined(ASIO_HAS_VARIADIC_TEMPLATES)

  template <typename Service, typename... Args>
  friend Service& make_service(execution_context& e,
      ASIO_MOVE_ARG(Args)... args);

#else // defined(ASIO_HAS_VARIADIC_TEMPLATES)

  template <typename Service>
  friend Service& make_service(execution_context& e);

#define ASIO_PRIVATE_MAKE_SERVICE_DEF(n) \
  template <typename Service, ASIO_VARIADIC_TPARAMS(n)> \
  friend Service& make_service(execution_context& e, \
      ASIO_VARIADIC_MOVE_PARAMS(n)); \
  
  ASIO_VARIADIC_GENERATE(ASIO_PRIVATE_MAKE_SERVICE_DEF)
#undef ASIO_PRIVATE_MAKE_SERVICE_DEF

#endif // defined(ASIO_HAS_VARIADIC_TEMPLATES)


  template <typename Service>
  friend void add_service(execution_context& e, Service* svc);


  template <typename Service>
  friend bool has_service(execution_context& e);

private:
  // The service registry.
  asio::detail::service_registry* service_registry_;
};

class execution_context::id
  : private noncopyable
{
public:
  id() {}
};

class execution_context::service
  : private noncopyable
{
public:
  execution_context& context();

protected:

  ASIO_DECL service(execution_context& owner);

  ASIO_DECL virtual ~service();

private:
  virtual void shutdown() = 0;


  ASIO_DECL virtual void notify_fork(
      execution_context::fork_event event);

  friend class asio::detail::service_registry;
  struct key
  {
    key() : type_info_(0), id_(0) {}
    const std::type_info* type_info_;
    const execution_context::id* id_;
  } key_;

  execution_context& owner_;
  service* next_;
};

class service_already_exists
  : public std::logic_error
{
public:
  ASIO_DECL service_already_exists();
};

class invalid_service_owner
  : public std::logic_error
{
public:
  ASIO_DECL invalid_service_owner();
};

namespace detail {

// Special derived service id type to keep classes header-file only.
template <typename Type>
class service_id
  : public execution_context::id
{
};

// Special service base class to keep classes header-file only.
template <typename Type>
class execution_context_service_base
  : public execution_context::service
{
public:
  static service_id<Type> id;

  // Constructor.
  execution_context_service_base(execution_context& e)
    : execution_context::service(e)
  {
  }
};

template <typename Type>
service_id<Type> execution_context_service_base<Type>::id;

} // namespace detail
} // namespace asio

#include "asio/detail/pop_options.hpp"

#include "asio/impl/execution_context.hpp"
#if defined(ASIO_HEADER_ONLY)
# include "asio/impl/execution_context.ipp"
#endif // defined(ASIO_HEADER_ONLY)

#endif // ASIO_EXECUTION_CONTEXT_HPP