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/Src/Dependencies/Boost/boost/asio/io_service.hpp

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  1//
  2// io_service.hpp
  3// ~~~~~~~~~~~~~~
  4//
  5// Copyright (c) 2003-2011 Christopher M. Kohlhoff (chris at kohlhoff dot com)
  6//
  7// Distributed under the Boost Software License, Version 1.0. (See accompanying
  8// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  9//
 10
 11#ifndef BOOST_ASIO_IO_SERVICE_HPP
 12#define BOOST_ASIO_IO_SERVICE_HPP
 13
 14#if defined(_MSC_VER) && (_MSC_VER >= 1200)
 15# pragma once
 16#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
 17
 18#include <boost/asio/detail/config.hpp>
 19#include <cstddef>
 20#include <stdexcept>
 21#include <typeinfo>
 22#include <boost/asio/detail/noncopyable.hpp>
 23#include <boost/asio/detail/service_registry_fwd.hpp>
 24#include <boost/asio/detail/wrapped_handler.hpp>
 25#include <boost/system/error_code.hpp>
 26
 27#if defined(BOOST_ASIO_HAS_IOCP)
 28# include <boost/asio/detail/win_iocp_io_service_fwd.hpp>
 29#else
 30# include <boost/asio/detail/task_io_service_fwd.hpp>
 31#endif
 32
 33#if defined(BOOST_WINDOWS) || defined(__CYGWIN__)
 34# include <boost/asio/detail/winsock_init.hpp>
 35#elif defined(__sun) || defined(__QNX__) || defined(__hpux) || defined(_AIX) \
 36  || defined(__osf__)
 37# include <boost/asio/detail/signal_init.hpp>
 38#endif
 39
 40#include <boost/asio/detail/push_options.hpp>
 41
 42namespace boost {
 43namespace asio {
 44
 45class io_service;
 46template <typename Service> Service& use_service(io_service& ios);
 47template <typename Service> void add_service(io_service& ios, Service* svc);
 48template <typename Service> bool has_service(io_service& ios);
 49
 50#if defined(BOOST_ASIO_HAS_IOCP)
 51namespace detail { typedef win_iocp_io_service io_service_impl; }
 52#else
 53namespace detail { typedef task_io_service io_service_impl; }
 54#endif
 55
 56/// Provides core I/O functionality.
 57/**
 58 * The io_service class provides the core I/O functionality for users of the
 59 * asynchronous I/O objects, including:
 60 *
 61 * @li boost::asio::ip::tcp::socket
 62 * @li boost::asio::ip::tcp::acceptor
 63 * @li boost::asio::ip::udp::socket
 64 * @li boost::asio::deadline_timer.
 65 *
 66 * The io_service class also includes facilities intended for developers of
 67 * custom asynchronous services.
 68 *
 69 * @par Thread Safety
 70 * @e Distinct @e objects: Safe.@n
 71 * @e Shared @e objects: Safe, with the specific exceptions of the reset() and
 72 * notify_fork() functions. Calling reset() while there are unfinished run(),
 73 * run_one(), poll() or poll_one() calls results in undefined behaviour. The
 74 * notify_fork() function should not be called while any io_service function,
 75 * or any function on an I/O object that is associated with the io_service, is
 76 * being called in another thread.
 77 *
 78 * @par Concepts:
 79 * Dispatcher.
 80 *
 81 * @par Synchronous and asynchronous operations
 82 *
 83 * Synchronous operations on I/O objects implicitly run the io_service object
 84 * for an individual operation. The io_service functions run(), run_one(),
 85 * poll() or poll_one() must be called for the io_service to perform
 86 * asynchronous operations on behalf of a C++ program. Notification that an
 87 * asynchronous operation has completed is delivered by invocation of the
 88 * associated handler. Handlers are invoked only by a thread that is currently
 89 * calling any overload of run(), run_one(), poll() or poll_one() for the
 90 * io_service.
 91 *
 92 * @par Effect of exceptions thrown from handlers
 93 *
 94 * If an exception is thrown from a handler, the exception is allowed to
 95 * propagate through the throwing thread's invocation of run(), run_one(),
 96 * poll() or poll_one(). No other threads that are calling any of these
 97 * functions are affected. It is then the responsibility of the application to
 98 * catch the exception.
 99 *
100 * After the exception has been caught, the run(), run_one(), poll() or
101 * poll_one() call may be restarted @em without the need for an intervening
102 * call to reset(). This allows the thread to rejoin the io_service object's
103 * thread pool without impacting any other threads in the pool.
104 *
105 * For example:
106 *
107 * @code
108 * boost::asio::io_service io_service;
109 * ...
110 * for (;;)
111 * {
112 *   try
113 *   {
114 *     io_service.run();
115 *     break; // run() exited normally
116 *   }
117 *   catch (my_exception& e)
118 *   {
119 *     // Deal with exception as appropriate.
120 *   }
121 * }
122 * @endcode
123 *
124 * @par Stopping the io_service from running out of work
125 *
126 * Some applications may need to prevent an io_service object's run() call from
127 * returning when there is no more work to do. For example, the io_service may
128 * be being run in a background thread that is launched prior to the
129 * application's asynchronous operations. The run() call may be kept running by
130 * creating an object of type boost::asio::io_service::work:
131 *
132 * @code boost::asio::io_service io_service;
133 * boost::asio::io_service::work work(io_service);
134 * ... @endcode
135 *
136 * To effect a shutdown, the application will then need to call the io_service
137 * object's stop() member function. This will cause the io_service run() call
138 * to return as soon as possible, abandoning unfinished operations and without
139 * permitting ready handlers to be dispatched.
140 *
141 * Alternatively, if the application requires that all operations and handlers
142 * be allowed to finish normally, the work object may be explicitly destroyed.
143 *
144 * @code boost::asio::io_service io_service;
145 * auto_ptr<boost::asio::io_service::work> work(
146 *     new boost::asio::io_service::work(io_service));
147 * ...
148 * work.reset(); // Allow run() to exit. @endcode
149 *
150 * @par The io_service class and I/O services
151 *
152 * Class io_service implements an extensible, type-safe, polymorphic set of I/O
153 * services, indexed by service type. An object of class io_service must be
154 * initialised before I/O objects such as sockets, resolvers and timers can be
155 * used. These I/O objects are distinguished by having constructors that accept
156 * an @c io_service& parameter.
157 *
158 * I/O services exist to manage the logical interface to the operating system on
159 * behalf of the I/O objects. In particular, there are resources that are shared
160 * across a class of I/O objects. For example, timers may be implemented in
161 * terms of a single timer queue. The I/O services manage these shared
162 * resources.
163 *
164 * Access to the services of an io_service is via three function templates,
165 * use_service(), add_service() and has_service().
166 *
167 * In a call to @c use_service<Service>(), the type argument chooses a service,
168 * making available all members of the named type. If @c Service is not present
169 * in an io_service, an object of type @c Service is created and added to the
170 * io_service. A C++ program can check if an io_service implements a
171 * particular service with the function template @c has_service<Service>().
172 *
173 * Service objects may be explicitly added to an io_service using the function
174 * template @c add_service<Service>(). If the @c Service is already present, the
175 * service_already_exists exception is thrown. If the owner of the service is
176 * not the same object as the io_service parameter, the invalid_service_owner
177 * exception is thrown.
178 *
179 * Once a service reference is obtained from an io_service object by calling
180 * use_service(), that reference remains usable as long as the owning io_service
181 * object exists.
182 *
183 * All I/O service implementations have io_service::service as a public base
184 * class. Custom I/O services may be implemented by deriving from this class and
185 * then added to an io_service using the facilities described above.
186 */
187class io_service
188  : private noncopyable
189{
190private:
191  typedef detail::io_service_impl impl_type;
192#if defined(BOOST_ASIO_HAS_IOCP)
193  friend class detail::win_iocp_overlapped_ptr;
194#endif
195
196public:
197  class work;
198  friend class work;
199
200  class id;
201
202  class service;
203
204  class strand;
205
206  /// Constructor.
207  BOOST_ASIO_DECL io_service();
208
209  /// Constructor.
210  /**
211   * Construct with a hint about the required level of concurrency.
212   *
213   * @param concurrency_hint A suggestion to the implementation on how many
214   * threads it should allow to run simultaneously.
215   */
216  BOOST_ASIO_DECL explicit io_service(std::size_t concurrency_hint);
217
218  /// Destructor.
219  /**
220   * On destruction, the io_service performs the following sequence of
221   * operations:
222   *
223   * @li For each service object @c svc in the io_service set, in reverse order
224   * of the beginning of service object lifetime, performs
225   * @c svc->shutdown_service().
226   *
227   * @li Uninvoked handler objects that were scheduled for deferred invocation
228   * on the io_service, or any associated strand, are destroyed.
229   *
230   * @li For each service object @c svc in the io_service set, in reverse order
231   * of the beginning of service object lifetime, performs
232   * <tt>delete static_cast<io_service::service*>(svc)</tt>.
233   *
234   * @note The destruction sequence described above permits programs to
235   * simplify their resource management by using @c shared_ptr<>. Where an
236   * object's lifetime is tied to the lifetime of a connection (or some other
237   * sequence of asynchronous operations), a @c shared_ptr to the object would
238   * be bound into the handlers for all asynchronous operations associated with
239   * it. This works as follows:
240   *
241   * @li When a single connection ends, all associated asynchronous operations
242   * complete. The corresponding handler objects are destroyed, and all
243   * @c shared_ptr references to the objects are destroyed.
244   *
245   * @li To shut down the whole program, the io_service function stop() is
246   * called to terminate any run() calls as soon as possible. The io_service
247   * destructor defined above destroys all handlers, causing all @c shared_ptr
248   * references to all connection objects to be destroyed.
249   */
250  BOOST_ASIO_DECL ~io_service();
251
252  /// Run the io_service object's event processing loop.
253  /**
254   * The run() function blocks until all work has finished and there are no
255   * more handlers to be dispatched, or until the io_service has been stopped.
256   *
257   * Multiple threads may call the run() function to set up a pool of threads
258   * from which the io_service may execute handlers. All threads that are
259   * waiting in the pool are equivalent and the io_service may choose any one
260   * of them to invoke a handler.
261   *
262   * A normal exit from the run() function implies that the io_service object
263   * is stopped (the stopped() function returns @c true). Subsequent calls to
264   * run(), run_one(), poll() or poll_one() will return immediately unless there
265   * is a prior call to reset().
266   *
267   * @return The number of handlers that were executed.
268   *
269   * @throws boost::system::system_error Thrown on failure.
270   *
271   * @note The run() function must not be called from a thread that is currently
272   * calling one of run(), run_one(), poll() or poll_one() on the same
273   * io_service object.
274   *
275   * The poll() function may also be used to dispatch ready handlers, but
276   * without blocking.
277   */
278  BOOST_ASIO_DECL std::size_t run();
279
280  /// Run the io_service object's event processing loop.
281  /**
282   * The run() function blocks until all work has finished and there are no
283   * more handlers to be dispatched, or until the io_service has been stopped.
284   *
285   * Multiple threads may call the run() function to set up a pool of threads
286   * from which the io_service may execute handlers. All threads that are
287   * waiting in the pool are equivalent and the io_service may choose any one
288   * of them to invoke a handler.
289   *
290   * A normal exit from the run() function implies that the io_service object
291   * is stopped (the stopped() function returns @c true). Subsequent calls to
292   * run(), run_one(), poll() or poll_one() will return immediately unless there
293   * is a prior call to reset().
294   *
295   * @param ec Set to indicate what error occurred, if any.
296   *
297   * @return The number of handlers that were executed.
298   *
299   * @note The run() function must not be called from a thread that is currently
300   * calling one of run(), run_one(), poll() or poll_one() on the same
301   * io_service object.
302   *
303   * The poll() function may also be used to dispatch ready handlers, but
304   * without blocking.
305   */
306  BOOST_ASIO_DECL std::size_t run(boost::system::error_code& ec);
307
308  /// Run the io_service object's event processing loop to execute at most one
309  /// handler.
310  /**
311   * The run_one() function blocks until one handler has been dispatched, or
312   * until the io_service has been stopped.
313   *
314   * @return The number of handlers that were executed. A zero return value
315   * implies that the io_service object is stopped (the stopped() function
316   * returns @c true). Subsequent calls to run(), run_one(), poll() or
317   * poll_one() will return immediately unless there is a prior call to
318   * reset().
319   *
320   * @throws boost::system::system_error Thrown on failure.
321   */
322  BOOST_ASIO_DECL std::size_t run_one();
323
324  /// Run the io_service object's event processing loop to execute at most one
325  /// handler.
326  /**
327   * The run_one() function blocks until one handler has been dispatched, or
328   * until the io_service has been stopped.
329   *
330   * @return The number of handlers that were executed. A zero return value
331   * implies that the io_service object is stopped (the stopped() function
332   * returns @c true). Subsequent calls to run(), run_one(), poll() or
333   * poll_one() will return immediately unless there is a prior call to
334   * reset().
335   *
336   * @return The number of handlers that were executed.
337   */
338  BOOST_ASIO_DECL std::size_t run_one(boost::system::error_code& ec);
339
340  /// Run the io_service object's event processing loop to execute ready
341  /// handlers.
342  /**
343   * The poll() function runs handlers that are ready to run, without blocking,
344   * until the io_service has been stopped or there are no more ready handlers.
345   *
346   * @return The number of handlers that were executed.
347   *
348   * @throws boost::system::system_error Thrown on failure.
349   */
350  BOOST_ASIO_DECL std::size_t poll();
351
352  /// Run the io_service object's event processing loop to execute ready
353  /// handlers.
354  /**
355   * The poll() function runs handlers that are ready to run, without blocking,
356   * until the io_service has been stopped or there are no more ready handlers.
357   *
358   * @param ec Set to indicate what error occurred, if any.
359   *
360   * @return The number of handlers that were executed.
361   */
362  BOOST_ASIO_DECL std::size_t poll(boost::system::error_code& ec);
363
364  /// Run the io_service object's event processing loop to execute one ready
365  /// handler.
366  /**
367   * The poll_one() function runs at most one handler that is ready to run,
368   * without blocking.
369   *
370   * @return The number of handlers that were executed.
371   *
372   * @throws boost::system::system_error Thrown on failure.
373   */
374  BOOST_ASIO_DECL std::size_t poll_one();
375
376  /// Run the io_service object's event processing loop to execute one ready
377  /// handler.
378  /**
379   * The poll_one() function runs at most one handler that is ready to run,
380   * without blocking.
381   *
382   * @param ec Set to indicate what error occurred, if any.
383   *
384   * @return The number of handlers that were executed.
385   */
386  BOOST_ASIO_DECL std::size_t poll_one(boost::system::error_code& ec);
387
388  /// Stop the io_service object's event processing loop.
389  /**
390   * This function does not block, but instead simply signals the io_service to
391   * stop. All invocations of its run() or run_one() member functions should
392   * return as soon as possible. Subsequent calls to run(), run_one(), poll()
393   * or poll_one() will return immediately until reset() is called.
394   */
395  BOOST_ASIO_DECL void stop();
396
397  /// Determine whether the io_service object has been stopped.
398  /**
399   * This function is used to determine whether an io_service object has been
400   * stopped, either through an explicit call to stop(), or due to running out
401   * of work. When an io_service object is stopped, calls to run(), run_one(),
402   * poll() or poll_one() will return immediately without invoking any
403   * handlers.
404   *
405   * @return @c true if the io_service object is stopped, otherwise @c false.
406   */
407  BOOST_ASIO_DECL bool stopped() const;
408
409  /// Reset the io_service in preparation for a subsequent run() invocation.
410  /**
411   * This function must be called prior to any second or later set of
412   * invocations of the run(), run_one(), poll() or poll_one() functions when a
413   * previous invocation of these functions returned due to the io_service
414   * being stopped or running out of work. After a call to reset(), the
415   * io_service object's stopped() function will return @c false.
416   *
417   * This function must not be called while there are any unfinished calls to
418   * the run(), run_one(), poll() or poll_one() functions.
419   */
420  BOOST_ASIO_DECL void reset();
421
422  /// Request the io_service to invoke the given handler.
423  /**
424   * This function is used to ask the io_service to execute the given handler.
425   *
426   * The io_service guarantees that the handler will only be called in a thread
427   * in which the run(), run_one(), poll() or poll_one() member functions is
428   * currently being invoked. The handler may be executed inside this function
429   * if the guarantee can be met.
430   *
431   * @param handler The handler to be called. The io_service will make
432   * a copy of the handler object as required. The function signature of the
433   * handler must be: @code void handler(); @endcode
434   *
435   * @note This function throws an exception only if:
436   *
437   * @li the handler's @c asio_handler_allocate function; or
438   *
439   * @li the handler's copy constructor
440   *
441   * throws an exception.
442   */
443  template <typename CompletionHandler>
444  void dispatch(BOOST_ASIO_MOVE_ARG(CompletionHandler) handler);
445
446  /// Request the io_service to invoke the given handler and return immediately.
447  /**
448   * This function is used to ask the io_service to execute the given handler,
449   * but without allowing the io_service to call the handler from inside this
450   * function.
451   *
452   * The io_service guarantees that the handler will only be called in a thread
453   * in which the run(), run_one(), poll() or poll_one() member functions is
454   * currently being invoked.
455   *
456   * @param handler The handler to be called. The io_service will make
457   * a copy of the handler object as required. The function signature of the
458   * handler must be: @code void handler(); @endcode
459   *
460   * @note This function throws an exception only if:
461   *
462   * @li the handler's @c asio_handler_allocate function; or
463   *
464   * @li the handler's copy constructor
465   *
466   * throws an exception.
467   */
468  template <typename CompletionHandler>
469  void post(BOOST_ASIO_MOVE_ARG(CompletionHandler) handler);
470
471  /// Create a new handler that automatically dispatches the wrapped handler
472  /// on the io_service.
473  /**
474   * This function is used to create a new handler function object that, when
475   * invoked, will automatically pass the wrapped handler to the io_service
476   * object's dispatch function.
477   *
478   * @param handler The handler to be wrapped. The io_service will make a copy
479   * of the handler object as required. The function signature of the handler
480   * must be: @code void handler(A1 a1, ... An an); @endcode
481   *
482   * @return A function object that, when invoked, passes the wrapped handler to
483   * the io_service object's dispatch function. Given a function object with the
484   * signature:
485   * @code R f(A1 a1, ... An an); @endcode
486   * If this function object is passed to the wrap function like so:
487   * @code io_service.wrap(f); @endcode
488   * then the return value is a function object with the signature
489   * @code void g(A1 a1, ... An an); @endcode
490   * that, when invoked, executes code equivalent to:
491   * @code io_service.dispatch(boost::bind(f, a1, ... an)); @endcode
492   */
493  template <typename Handler>
494#if defined(GENERATING_DOCUMENTATION)
495  unspecified
496#else
497  detail::wrapped_handler<io_service&, Handler>
498#endif
499  wrap(Handler handler);
500
501  /// Fork-related event notifications.
502  enum fork_event
503  {
504    /// Notify the io_service that the process is about to fork.
505    fork_prepare,
506
507    /// Notify the io_service that the process has forked and is the parent.
508    fork_parent,
509
510    /// Notify the io_service that the process has forked and is the child.
511    fork_child
512  };
513
514  /// Notify the io_service of a fork-related event.
515  /**
516   * This function is used to inform the io_service that the process is about
517   * to fork, or has just forked. This allows the io_service, and the services
518   * it contains, to perform any necessary housekeeping to ensure correct
519   * operation following a fork.
520   *
521   * This function must not be called while any other io_service function, or
522   * any function on an I/O object associated with the io_service, is being
523   * called in another thread. It is, however, safe to call this function from
524   * within a completion handler, provided no other thread is accessing the
525   * io_service.
526   *
527   * @param event A fork-related event.
528   *
529   * @throws boost::system::system_error Thrown on failure. If the notification
530   * fails the io_service object should no longer be used and should be
531   * destroyed.
532   *
533   * @par Example
534   * The following code illustrates how to incorporate the notify_fork()
535   * function:
536   * @code my_io_service.notify_fork(boost::asio::io_service::fork_prepare);
537   * if (fork() == 0)
538   * {
539   *   // This is the child process.
540   *   my_io_service.notify_fork(boost::asio::io_service::fork_child);
541   * }
542   * else
543   * {
544   *   // This is the parent process.
545   *   my_io_service.notify_fork(boost::asio::io_service::fork_parent);
546   * } @endcode
547   *
548   * @note For each service object @c svc in the io_service set, performs
549   * <tt>svc->fork_service();</tt>. When processing the fork_prepare event,
550   * services are visited in reverse order of the beginning of service object
551   * lifetime. Otherwise, services are visited in order of the beginning of
552   * service object lifetime.
553   */
554  BOOST_ASIO_DECL void notify_fork(boost::asio::io_service::fork_event event);
555
556  /// Obtain the service object corresponding to the given type.
557  /**
558   * This function is used to locate a service object that corresponds to
559   * the given service type. If there is no existing implementation of the
560   * service, then the io_service will create a new instance of the service.
561   *
562   * @param ios The io_service object that owns the service.
563   *
564   * @return The service interface implementing the specified service type.
565   * Ownership of the service interface is not transferred to the caller.
566   */
567  template <typename Service>
568  friend Service& use_service(io_service& ios);
569
570  /// Add a service object to the io_service.
571  /**
572   * This function is used to add a service to the io_service.
573   *
574   * @param ios The io_service object that owns the service.
575   *
576   * @param svc The service object. On success, ownership of the service object
577   * is transferred to the io_service. When the io_service object is destroyed,
578   * it will destroy the service object by performing:
579   * @code delete static_cast<io_service::service*>(svc) @endcode
580   *
581   * @throws boost::asio::service_already_exists Thrown if a service of the
582   * given type is already present in the io_service.
583   *
584   * @throws boost::asio::invalid_service_owner Thrown if the service's owning
585   * io_service is not the io_service object specified by the ios parameter.
586   */
587  template <typename Service>
588  friend void add_service(io_service& ios, Service* svc);
589
590  /// Determine if an io_service contains a specified service type.
591  /**
592   * This function is used to determine whether the io_service contains a
593   * service object corresponding to the given service type.
594   *
595   * @param ios The io_service object that owns the service.
596   *
597   * @return A boolean indicating whether the io_service contains the service.
598   */
599  template <typename Service>
600  friend bool has_service(io_service& ios);
601
602private:
603#if defined(BOOST_WINDOWS) || defined(__CYGWIN__)
604  detail::winsock_init<> init_;
605#elif defined(__sun) || defined(__QNX__) || defined(__hpux) || defined(_AIX) \
606  || defined(__osf__)
607  detail::signal_init<> init_;
608#endif
609
610  // The service registry.
611  boost::asio::detail::service_registry* service_registry_;
612
613  // The implementation.
614  impl_type& impl_;
615};
616
617/// Class to inform the io_service when it has work to do.
618/**
619 * The work class is used to inform the io_service when work starts and
620 * finishes. This ensures that the io_service object's run() function will not
621 * exit while work is underway, and that it does exit when there is no
622 * unfinished work remaining.
623 *
624 * The work class is copy-constructible so that it may be used as a data member
625 * in a handler class. It is not assignable.
626 */
627class io_service::work
628{
629public:
630  /// Constructor notifies the io_service that work is starting.
631  /**
632   * The constructor is used to inform the io_service that some work has begun.
633   * This ensures that the io_service object's run() function will not exit
634   * while the work is underway.
635   */
636  explicit work(boost::asio::io_service& io_service);
637
638  /// Copy constructor notifies the io_service that work is starting.
639  /**
640   * The constructor is used to inform the io_service that some work has begun.
641   * This ensures that the io_service object's run() function will not exit
642   * while the work is underway.
643   */
644  work(const work& other);
645
646  /// Destructor notifies the io_service that the work is complete.
647  /**
648   * The destructor is used to inform the io_service that some work has
649   * finished. Once the count of unfinished work reaches zero, the io_service
650   * object's run() function is permitted to exit.
651   */
652  ~work();
653
654  /// Get the io_service associated with the work.
655  boost::asio::io_service& get_io_service();
656
657private:
658  // Prevent assignment.
659  void operator=(const work& other);
660
661  // The io_service.
662  boost::asio::io_service& io_service_;
663};
664
665/// Class used to uniquely identify a service.
666class io_service::id
667  : private noncopyable
668{
669public:
670  /// Constructor.
671  id() {}
672};
673
674/// Base class for all io_service services.
675class io_service::service
676  : private noncopyable
677{
678public:
679  /// Get the io_service object that owns the service.
680  boost::asio::io_service& get_io_service();
681
682protected:
683  /// Constructor.
684  /**
685   * @param owner The io_service object that owns the service.
686   */
687  BOOST_ASIO_DECL service(boost::asio::io_service& owner);
688
689  /// Destructor.
690  BOOST_ASIO_DECL virtual ~service();
691
692private:
693  /// Destroy all user-defined handler objects owned by the service.
694  virtual void shutdown_service() = 0;
695
696  /// Handle notification of a fork-related event to perform any necessary
697  /// housekeeping.
698  /**
699   * This function is not a pure virtual so that services only have to
700   * implement it if necessary. The default implementation does nothing.
701   */
702  BOOST_ASIO_DECL virtual void fork_service(
703      boost::asio::io_service::fork_event event);
704
705  friend class boost::asio::detail::service_registry;
706  struct key
707  {
708    key() : type_info_(0), id_(0) {}
709    const std::type_info* type_info_;
710    const boost::asio::io_service::id* id_;
711  } key_;
712
713  boost::asio::io_service& owner_;
714  service* next_;
715};
716
717/// Exception thrown when trying to add a duplicate service to an io_service.
718class service_already_exists
719  : public std::logic_error
720{
721public:
722  BOOST_ASIO_DECL service_already_exists();
723};
724
725/// Exception thrown when trying to add a service object to an io_service where
726/// the service has a different owner.
727class invalid_service_owner
728  : public std::logic_error
729{
730public:
731  BOOST_ASIO_DECL invalid_service_owner();
732};
733
734namespace detail {
735
736// Special derived service id type to keep classes header-file only.
737template <typename Type>
738class service_id
739  : public boost::asio::io_service::id
740{
741};
742
743// Special service base class to keep classes header-file only.
744template <typename Type>
745class service_base
746  : public boost::asio::io_service::service
747{
748public:
749  static boost::asio::detail::service_id<Type> id;
750
751  // Constructor.
752  service_base(boost::asio::io_service& io_service)
753    : boost::asio::io_service::service(io_service)
754  {
755  }
756};
757
758template <typename Type>
759boost::asio::detail::service_id<Type> service_base<Type>::id;
760
761} // namespace detail
762} // namespace asio
763} // namespace boost
764
765#include <boost/asio/detail/pop_options.hpp>
766
767#include <boost/asio/impl/io_service.hpp>
768#if defined(BOOST_ASIO_HEADER_ONLY)
769# include <boost/asio/impl/io_service.ipp>
770#endif // defined(BOOST_ASIO_HEADER_ONLY)
771
772#endif // BOOST_ASIO_IO_SERVICE_HPP