// // io_service.hpp // ~~~~~~~~~~~~~~ // // Copyright (c) 2003-2010 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 BOOST_ASIO_IO_SERVICE_HPP #define BOOST_ASIO_IO_SERVICE_HPP #if defined(_MSC_VER) && (_MSC_VER >= 1200) # pragma once #endif // defined(_MSC_VER) && (_MSC_VER >= 1200) #include <boost/asio/detail/push_options.hpp> #include <boost/asio/detail/push_options.hpp> #include <cstddef> #include <stdexcept> #include <typeinfo> #include <boost/config.hpp> #include <boost/throw_exception.hpp> #include <boost/system/error_code.hpp> #include <boost/asio/detail/pop_options.hpp> #include <boost/asio/detail/noncopyable.hpp> #include <boost/asio/detail/reactor_fwd.hpp> #include <boost/asio/detail/service_registry_fwd.hpp> #include <boost/asio/detail/signal_init.hpp> #include <boost/asio/detail/task_io_service_fwd.hpp> #include <boost/asio/detail/win_iocp_io_service_fwd.hpp> #include <boost/asio/detail/winsock_init.hpp> #include <boost/asio/detail/wrapped_handler.hpp> namespace boost { namespace asio { class io_service; template <typename Service> Service& use_service(io_service& ios); template <typename Service> void add_service(io_service& ios, Service* svc); template <typename Service> bool has_service(io_service& ios); #if defined(BOOST_ASIO_HAS_IOCP) namespace detail { typedef win_iocp_io_service io_service_impl; } #else namespace detail { typedef task_io_service<reactor> io_service_impl; } #endif /// Provides core I/O functionality. /** * The io_service class provides the core I/O functionality for users of the * asynchronous I/O objects, including: * * @li boost::asio::ip::tcp::socket * @li boost::asio::ip::tcp::acceptor * @li boost::asio::ip::udp::socket * @li boost::asio::deadline_timer. * * The io_service class also includes facilities intended for developers of * custom asynchronous services. * * @par Thread Safety * @e Distinct @e objects: Safe.@n * @e Shared @e objects: Safe, with the exception that calling reset() while * there are unfinished run(), run_one(), poll() or poll_one() calls results in * undefined behaviour. * * @par Concepts: * Dispatcher. * * @par Synchronous and asynchronous operations * * Synchronous operations on I/O objects implicitly run the io_service object * for an individual operation. The io_service functions run(), run_one(), * poll() or poll_one() must be called for the io_service to perform * asynchronous operations on behalf of a C++ program. Notification that an * asynchronous operation has completed is delivered by invocation of the * associated handler. Handlers are invoked only by a thread that is currently * calling any overload of run(), run_one(), poll() or poll_one() for the * io_service. * * @par Effect of exceptions thrown from handlers * * If an exception is thrown from a handler, the exception is allowed to * propagate through the throwing thread's invocation of run(), run_one(), * poll() or poll_one(). No other threads that are calling any of these * functions are affected. It is then the responsibility of the application to * catch the exception. * * After the exception has been caught, the run(), run_one(), poll() or * poll_one() call may be restarted @em without the need for an intervening * call to reset(). This allows the thread to rejoin the io_service object's * thread pool without impacting any other threads in the pool. * * For example: * * @code * boost::asio::io_service io_service; * ... * for (;;) * { * try * { * io_service.run(); * break; // run() exited normally * } * catch (my_exception& e) * { * // Deal with exception as appropriate. * } * } * @endcode * * @par Stopping the io_service from running out of work * * Some applications may need to prevent an io_service object's run() call from * returning when there is no more work to do. For example, the io_service may * be being run in a background thread that is launched prior to the * application's asynchronous operations. The run() call may be kept running by * creating an object of type boost::asio::io_service::work: * * @code boost::asio::io_service io_service; * boost::asio::io_service::work work(io_service); * ... @endcode * * To effect a shutdown, the application will then need to call the io_service * object's stop() member function. This will cause the io_service run() call * to return as soon as possible, abandoning unfinished operations and without * permitting ready handlers to be dispatched. * * Alternatively, if the application requires that all operations and handlers * be allowed to finish normally, the work object may be explicitly destroyed. * * @code boost::asio::io_service io_service; * auto_ptr<boost::asio::io_service::work> work( * new boost::asio::io_service::work(io_service)); * ... * work.reset(); // Allow run() to exit. @endcode * * @par The io_service class and I/O services * * Class io_service implements an extensible, type-safe, polymorphic set of I/O * services, indexed by service type. An object of class io_service must be * initialised before I/O objects such as sockets, resolvers and timers can be * used. These I/O objects are distinguished by having constructors that accept * an @c io_service& parameter. * * I/O services exist to manage the logical interface to the operating system on * behalf of the I/O objects. In particular, there are resources that are shared * across a class of I/O objects. For example, timers may be implemented in * terms of a single timer queue. The I/O services manage these shared * resources. * * Access to the services of an io_service is via three function templates, * use_service(), add_service() and has_service(). * * In a call to @c use_service<Service>(), the type argument chooses a service, * making available all members of the named type. If @c Service is not present * in an io_service, an object of type @c Service is created and added to the * io_service. A C++ program can check if an io_service implements a * particular service with the function template @c has_service<Service>(). * * Service objects may be explicitly added to an io_service using the function * template @c add_service<Service>(). If the @c Service is already present, the * service_already_exists exception is thrown. If the owner of the service is * not the same object as the io_service parameter, the invalid_service_owner * exception is thrown. * * Once a service reference is obtained from an io_service object by calling * use_service(), that reference remains usable as long as the owning io_service * object exists. * * All I/O service implementations have io_service::service as a public base * class. Custom I/O services may be implemented by deriving from this class and * then added to an io_service using the facilities described above. */ class io_service : private noncopyable { private: typedef detail::io_service_impl impl_type; #if defined(BOOST_ASIO_HAS_IOCP) friend class detail::win_iocp_overlapped_ptr; #endif public: class work; friend class work; class id; class service; class strand; /// Constructor. io_service(); /// Constructor. /** * Construct with a hint about the required level of concurrency. * * @param concurrency_hint A suggestion to the implementation on how many * threads it should allow to run simultaneously. */ explicit io_service(std::size_t concurrency_hint); /// Destructor. /** * On destruction, the io_service performs the following sequence of * operations: * * @li For each service object @c svc in the io_service set, in reverse order * of the beginning of service object lifetime, performs * @c svc->shutdown_service(). * * @li Uninvoked handler objects that were scheduled for deferred invocation * on the io_service, or any associated strand, are destroyed. * * @li For each service object @c svc in the io_service set, in reverse order * of the beginning of service object lifetime, performs * <tt>delete static_cast<io_service::service*>(svc)</tt>. * * @note The destruction sequence described above permits programs to * simplify their resource management by using @c shared_ptr<>. Where an * object's lifetime is tied to the lifetime of a connection (or some other * sequence of asynchronous operations), a @c shared_ptr to the object would * be bound into the handlers for all asynchronous operations associated with * it. This works as follows: * * @li When a single connection ends, all associated asynchronous operations * complete. The corresponding handler objects are destroyed, and all * @c shared_ptr references to the objects are destroyed. * * @li To shut down the whole program, the io_service function stop() is * called to terminate any run() calls as soon as possible. The io_service * destructor defined above destroys all handlers, causing all @c shared_ptr * references to all connection objects to be destroyed. */ ~io_service(); /// Run the io_service object's event processing loop. /** * The run() function blocks until all work has finished and there are no * more handlers to be dispatched, or until the io_service has been stopped. * * Multiple threads may call the run() function to set up a pool of threads * from which the io_service may execute handlers. All threads that are * waiting in the pool are equivalent and the io_service may choose any one * of them to invoke a handler. * * The run() function may be safely called again once it has completed only * after a call to reset(). * * @return The number of handlers that were executed. * * @throws boost::system::system_error Thrown on failure. * * @note The run() function must not be called from a thread that is currently * calling one of run(), run_one(), poll() or poll_one() on the same * io_service object. * * The poll() function may also be used to dispatch ready handlers, but * without blocking. */ std::size_t run(); /// Run the io_service object's event processing loop. /** * The run() function blocks until all work has finished and there are no * more handlers to be dispatched, or until the io_service has been stopped. * * Multiple threads may call the run() function to set up a pool of threads * from which the io_service may execute handlers. All threads that are * waiting in the pool are equivalent and the io_service may choose any one * of them to invoke a handler. * * The run() function may be safely called again once it has completed only * after a call to reset(). * * @param ec Set to indicate what error occurred, if any. * * @return The number of handlers that were executed. * * @note The run() function must not be called from a thread that is currently * calling one of run(), run_one(), poll() or poll_one() on the same * io_service object. * * The poll() function may also be used to dispatch ready handlers, but * without blocking. */ std::size_t run(boost::system::error_code& ec); /// Run the io_service object's event processing loop to execute at most one /// handler. /** * The run_one() function blocks until one handler has been dispatched, or * until the io_service has been stopped. * * @return The number of handlers that were executed. * * @throws boost::system::system_error Thrown on failure. */ std::size_t run_one(); /// Run the io_service object's event processing loop to execute at most one /// handler. /** * The run_one() function blocks until one handler has been dispatched, or * until the io_service has been stopped. * * @param ec Set to indicate what error occurred, if any. * * @return The number of handlers that were executed. */ std::size_t run_one(boost::system::error_code& ec); /// Run the io_service object's event processing loop to execute ready /// handlers. /** * The poll() function runs handlers that are ready to run, without blocking, * until the io_service has been stopped or there are no more ready handlers. * * @return The number of handlers that were executed. * * @throws boost::system::system_error Thrown on failure. */ std::size_t poll(); /// Run the io_service object's event processing loop to execute ready /// handlers. /** * The poll() function runs handlers that are ready to run, without blocking, * until the io_service has been stopped or there are no more ready handlers. * * @param ec Set to indicate what error occurred, if any. * * @return The number of handlers that were executed. */ std::size_t poll(boost::system::error_code& ec); /// Run the io_service object's event processing loop to execute one ready /// handler. /** * The poll_one() function runs at most one handler that is ready to run, * without blocking. * * @return The number of handlers that were executed. * * @throws boost::system::system_error Thrown on failure. */ std::size_t poll_one(); /// Run the io_service object's event processing loop to execute one ready /// handler. /** * The poll_one() function runs at most one handler that is ready to run, * without blocking. * * @param ec Set to indicate what error occurred, if any. * * @return The number of handlers that were executed. */ std::size_t poll_one(boost::system::error_code& ec); /// Stop the io_service object's event processing loop. /** * This function does not block, but instead simply signals the io_service to * stop. All invocations of its run() or run_one() member functions should * return as soon as possible. Subsequent calls to run(), run_one(), poll() * or poll_one() will return immediately until reset() is called. */ void stop(); /// Reset the io_service in preparation for a subsequent run() invocation. /** * This function must be called prior to any second or later set of * invocations of the run(), run_one(), poll() or poll_one() functions when a * previous invocation of these functions returned due to the io_service * being stopped or running out of work. This function allows the io_service * to reset any internal state, such as a "stopped" flag. * * This function must not be called while there are any unfinished calls to * the run(), run_one(), poll() or poll_one() functions. */ void reset(); /// Request the io_service to invoke the given handler. /** * This function is used to ask the io_service to execute the given handler. * * The io_service guarantees that the handler will only be called in a thread * in which the run(), run_one(), poll() or poll_one() member functions is * currently being invoked. The handler may be executed inside this function * if the guarantee can be met. * * @param handler The handler to be called. The io_service will make * a copy of the handler object as required. The function signature of the * handler must be: @code void handler(); @endcode * * @note This function throws an exception only if: * * @li the handler's @c asio_handler_allocate function; or * * @li the handler's copy constructor * * throws an exception. */ template <typename CompletionHandler> void dispatch(CompletionHandler handler); /// Request the io_service to invoke the given handler and return immediately. /** * This function is used to ask the io_service to execute the given handler, * but without allowing the io_service to call the handler from inside this * function. * * The io_service guarantees that the handler will only be called in a thread * in which the run(), run_one(), poll() or poll_one() member functions is * currently being invoked. * * @param handler The handler to be called. The io_service will make * a copy of the handler object as required. The function signature of the * handler must be: @code void handler(); @endcode * * @note This function throws an exception only if: * * @li the handler's @c asio_handler_allocate function; or * * @li the handler's copy constructor * * throws an exception. */ template <typename CompletionHandler> void post(CompletionHandler handler); /// Create a new handler that automatically dispatches the wrapped handler /// on the io_service. /** * This function is used to create a new handler function object that, when * invoked, will automatically pass the wrapped handler to the io_service * object's dispatch function. * * @param handler The handler to be wrapped. The io_service will make a copy * of the handler object as required. The function signature of the handler * must be: @code void handler(A1 a1, ... An an); @endcode * * @return A function object that, when invoked, passes the wrapped handler to * the io_service object's dispatch function. Given a function object with the * signature: * @code R f(A1 a1, ... An an); @endcode * If this function object is passed to the wrap function like so: * @code io_service.wrap(f); @endcode * then the return value is a function object with the signature * @code void g(A1 a1, ... An an); @endcode * that, when invoked, executes code equivalent to: * @code io_service.dispatch(boost::bind(f, a1, ... an)); @endcode */ template <typename Handler> #if defined(GENERATING_DOCUMENTATION) unspecified #else detail::wrapped_handler<io_service&, Handler> #endif wrap(Handler handler); /// Obtain the service object corresponding to the given type. /** * This function is used to locate a service object that corresponds to * the given service type. If there is no existing implementation of the * service, then the io_service will create a new instance of the service. * * @param ios The io_service object that owns the service. * * @return The service interface implementing the specified service type. * Ownership of the service interface is not transferred to the caller. */ template <typename Service> friend Service& use_service(io_service& ios); /// Add a service object to the io_service. /** * This function is used to add a service to the io_service. * * @param ios The io_service object that owns the service. * * @param svc The service object. On success, ownership of the service object * is transferred to the io_service. When the io_service object is destroyed, * it will destroy the service object by performing: * @code delete static_cast<io_service::service*>(svc) @endcode * * @throws boost::asio::service_already_exists Thrown if a service of the * given type is already present in the io_service. * * @throws boost::asio::invalid_service_owner Thrown if the service's owning * io_service is not the io_service object specified by the ios parameter. */ template <typename Service> friend void add_service(io_service& ios, Service* svc); /// Determine if an io_service contains a specified service type. /** * This function is used to determine whether the io_service contains a * service object corresponding to the given service type. * * @param ios The io_service object that owns the service. * * @return A boolean indicating whether the io_service contains the service. */ template <typename Service> friend bool has_service(io_service& ios); private: #if defined(BOOST_WINDOWS) || defined(__CYGWIN__) detail::winsock_init<> init_; #elif defined(__sun) || defined(__QNX__) || defined(__hpux) || defined(_AIX) \ || defined(__osf__) detail::signal_init<> init_; #endif // The service registry. boost::asio::detail::service_registry* service_registry_; // The implementation. impl_type& impl_; }; /// Class to inform the io_service when it has work to do. /** * The work class is used to inform the io_service when work starts and * finishes. This ensures that the io_service object's run() function will not * exit while work is underway, and that it does exit when there is no * unfinished work remaining. * * The work class is copy-constructible so that it may be used as a data member * in a handler class. It is not assignable. */ class io_service::work { public: /// Constructor notifies the io_service that work is starting. /** * The constructor is used to inform the io_service that some work has begun. * This ensures that the io_service object's run() function will not exit * while the work is underway. */ explicit work(boost::asio::io_service& io_service); /// Copy constructor notifies the io_service that work is starting. /** * The constructor is used to inform the io_service that some work has begun. * This ensures that the io_service object's run() function will not exit * while the work is underway. */ work(const work& other); /// Destructor notifies the io_service that the work is complete. /** * The destructor is used to inform the io_service that some work has * finished. Once the count of unfinished work reaches zero, the io_service * object's run() function is permitted to exit. */ ~work(); /// (Deprecated: use get_io_service().) Get the io_service associated with the /// work. boost::asio::io_service& io_service(); /// Get the io_service associated with the work. boost::asio::io_service& get_io_service(); private: // Prevent assignment. void operator=(const work& other); // The io_service. boost::asio::io_service& io_service_; }; /// Class used to uniquely identify a service. class io_service::id : private noncopyable { public: /// Constructor. id() {} }; /// Base class for all io_service services. class io_service::service : private noncopyable { public: /// (Deprecated: use get_io_service().) Get the io_service object that owns /// the service. boost::asio::io_service& io_service(); /// Get the io_service object that owns the service. boost::asio::io_service& get_io_service(); protected: /// Constructor. /** * @param owner The io_service object that owns the service. */ service(boost::asio::io_service& owner); /// Destructor. virtual ~service(); private: /// Destroy all user-defined handler objects owned by the service. virtual void shutdown_service() = 0; friend class boost::asio::detail::service_registry; struct key { key() : type_info_(0), id_(0) {} const std::type_info* type_info_; const boost::asio::io_service::id* id_; } key_; boost::asio::io_service& owner_; service* next_; }; /// Exception thrown when trying to add a duplicate service to an io_service. class service_already_exists : public std::logic_error { public: service_already_exists() : std::logic_error("Service already exists.") { } }; /// Exception thrown when trying to add a service object to an io_service where /// the service has a different owner. class invalid_service_owner : public std::logic_error { public: invalid_service_owner() : std::logic_error("Invalid service owner.") { } }; } // namespace asio } // namespace boost #include <boost/asio/impl/io_service.ipp> #include <boost/asio/detail/pop_options.hpp> #endif // BOOST_ASIO_IO_SERVICE_HPP