boost::asio::io_service
/// Provides core I/O functionality.
/**
* The io_service class provides the core I/O functionality for users of the
* asynchronous I/O objects, including:
* io_service类为下面的异步对象提供了核心的I/O操作函数
*
* @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 specific exceptions of the reset() and
* notify_fork() functions. Calling reset() while there are unfinished run(),
* run_one(), poll() or poll_one() calls results in undefined behaviour. The
* notify_fork() function should not be called while any io_service function,
* or any function on an I/O object that is associated with the io_service, is
* being called in another thread.
* 当run、run_one、poll、poll_one这些函数没有完成时，调用reset会引起未定义的行为。
* 如果有其它进程正在调用io_service的任何函数或者任何I/O对象的函数（这些I/O对象与
* io_service有关），则一定不要调用notify_fork()函数。
*
* @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.
* 在I/O对象上的同步操作会隐式的调用io_service对象。在c++程序中，io_service如果要完成异步操作，必须
* 调用run、run_one、poll、poll_one。 异步操作完成是指分发调用相关的处理句柄。
*
* @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.
* 假如一个回调句柄抛出异常，这个异常可以传播给那些调用run、run_one、poll、pool_one
* 的进程，其它没有调用这些函数的进程不受影响。然后应用程序有责任捕捉这个异常。
*
* 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.
* 捕捉异常后，run、run_one、poll、poll_one可以被重新调用，不需要再调用reset。
* 这允许进程重新加入io_service对象的进程池，从而不影响其他已经在进程池中的进程。
* 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:
* //add by wyp// work类可以阻止io_service的run函数在无任何任务时返回。这在后台服务的进程
* 中经常用到。
*
* @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.
* //stop()函数可以停止io_service,这将导致run()函数立即返回，那些未完成的操作被终止，
* 那些满足条件的句柄不能被分发。
*
* 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.
* io_service实现了可扩张的、类型安全的、多态的I/O服务集，按服务类型索引。在使用I/O对象
* 之前，必须初始化一个io_service对象。I/O对象通过接受一个io_service对象的引用区分。
*
* 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>().
* 通过调用use_service，类型参数选择一个Service，这种类型的所有成员就可以使用了。
* 如果Service不在一个io_service，就会创建一个type的Service，并把这个Service加入到io_service。
* 在c++程序中，我们可以用has_service来检查一个io_service对象是否存在一个特殊的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.
* Service 对象可以通过add_service加入io_service对象中，加入这个Service对象已经存在，
* 会抛出一个service已经存在的异常。 如果service的拥有者不和参数io_service是同一个对象，
* 会抛出无效的service拥有者的异常。
*
* 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.
* 一旦通过调用use_service获得一个service的引用，那么这个引用一直有效，只要这个service的
* 拥有者存在。
*
* 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.
BOOST_ASIO_DECL io_service();
/// Constructor.
/**
* Construct with a hint about the required level of concurrency（并发性）.
*
* @param concurrency_hint A suggestion to the implementation on how many
* threads it should allow to run simultaneously.//同时运行多少个进程
*/
BOOST_ASIO_DECL 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().
* 按进入队列的顺序，反序的调用service的shutdown_service
*
* @li Uninvoked handler objects that were scheduled for deferred invocation
* on the io_service, or any associated strand, are destroyed.
* 销毁延迟调用的句柄对象和相关的strand
*
* @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>.
* 按进入队列的顺序，反序的销毁service对象
*
* @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:
* 可以用shared_ptr来管理资源。当一个对象的生命期被绑定到一个连接或其他的异步操作，
* shared_ptr管理的资源对象会被绑定到所有异步操作的处理句柄上。
*
* @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.
* 当一个连接结束时，所有的异步操作完成。对应的处理句柄对象被销毁，并且所有对这些对象的
* shared_ptr的引用被销毁。
*
* @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.
* 结束程序时，io_service的stop函数被调用，立即终结所有run函数。
* io_service的析构会销毁所有的句柄对象，并且所有对这些对象的shared_ptr的引用被销毁。
*
*/
BOOST_ASIO_DECL ~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.
* run函数会阻塞程序直到所有的工作已经完成，即没有处理句柄需要去分发，或者
* io_service被停止。
*
* 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.
* 多线程可以创建一个线程池，每个线程都去调用io_service的run函数来执行分发句柄。
* 线程池中的线程平等的等待，并且io_service可以选择其中的任何一个线程去唤醒句柄。
*
* A normal exit from the run() function implies that the io_service object
* is stopped (the stopped() function returns @c true). Subsequent calls to
* run(), run_one(), poll() or poll_one() will return immediately unless there
* is a prior call to reset().
* 如果stopped()返回值为true，则run()正常退出，io_service服务已经停止,下一个调用
* run、run_one、poll、poll_one等会立即返回，除非程序程序调用了具有优先调用权的reset函数。
* reset函数会为下次调用run函数做好准备。
*
* @return The number of handlers that were executed.
* 返回执行的毁掉函数个数
*
* @throws boost::system::system_error Thrown on failure.
* 抛出 boost::system::system_error 如果出现错误。
*
* @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.
* 如果一个进程正在调用io_service对象的run、run_one、poll、poll_one这些函数中的一个，那么
* 这个进程不能再次调用此io_service对象的run函数。
*
* The poll() function may also be used to dispatch ready handlers, but
* without blocking.
* poll函数也可以分发已经就绪的处理句柄，但是poll不会阻塞。
*/
BOOST_ASIO_DECL 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.
*
* A normal exit from the run() function implies that the io_service object
* is stopped (the stopped() function returns @c true). Subsequent calls to
* run(), run_one(), poll() or poll_one() will return immediately unless there
* is a prior call to reset().
*
* @param ec Set to indicate what error occurred, if any.
* 如果调用过程出现错误，ec参数会被设置，指出程序出现什么错误。
*
* @return The number of handlers that were executed.
* 返回已经执行的处理句柄的个数。
*
* @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.
*/
BOOST_ASIO_DECL 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.
* run_one函数会阻塞直到一个处理句柄被分发或者io_service已经停止
*
* @return The number of handlers that were executed. A zero return value
* implies that the io_service object is stopped (the stopped() function
* returns @c true). Subsequent calls to run(), run_one(), poll() or
* poll_one() will return immediately unless there is a prior call to
* reset().
* 返回已经执行的处理句柄个数。返回值为0说明io_service对象已经停止工作，下一个
* 调用run、run_one、poll、poll_one会立即返回，除非调用了具有优先调用的reset函数。
* reset函数会为下次调用run函数做好准备。
*
* @throws boost::system::system_error Thrown on failure.
* 如果调用出现错误， 抛出boost::systerm::systerm_error
*/
BOOST_ASIO_DECL 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.
*
* @return The number of handlers that were executed. A zero return value
* implies that the io_service object is stopped (the stopped() function
* returns @c true). Subsequent calls to run(), run_one(), poll() or
* poll_one() will return immediately unless there is a prior call to
* reset().
*
* @return The number of handlers that were executed.
*
*/
BOOST_ASIO_DECL 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.
* poll函数会运行已经准备好去执行的处理句柄，直到即没有处理句柄需要去分发或者
* io_service被停止。这个函数的调用时无阻塞的。
*
* @return The number of handlers that were executed.
* 返回已经执行的处理句柄的个数。
*
* @throws boost::system::system_error Thrown on failure.
* 如果调用出现错误，会抛出boost::systerm::error
*
*/
BOOST_ASIO_DECL 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.
* 如果调用出现错误，参数ec会被设置，指出是什么错误。
*
* @return The number of handlers that were executed.
*/
BOOST_ASIO_DECL 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.
* poll_one函数最多运行一个准备执行的处理句柄，并且这个函数不会阻塞。
*
* @return The number of handlers that were executed.
* 返回已经执行的处理句柄的个数
*
* @throws boost::system::system_error Thrown on failure.
* 如果调用出现错误，会抛出boost::systerm::systerm_error
*
*/
BOOST_ASIO_DECL 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.
*/
BOOST_ASIO_DECL 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.
* stop函数不会阻塞，而是发出信号通知io_service停止。所有run、run_one、poll、poll_one
* 的调用会尽快返回。下一个调用run、run_one、poll、poll_one会立即返回，除非调用了具有
* 优先调用的reset函数。reset函数会为下次调用run函数做好准备。
*
*/
BOOST_ASIO_DECL void stop();
/// Determine whether the io_service object has been stopped.
/**
* This function is used to determine whether an io_service object has been
* stopped, either through an explicit call to stop(), or due to running out
* of work. When an io_service object is stopped, calls to run(), run_one(),
* poll() or poll_one() will return immediately without invoking any
* handlers.
* stopped函数可以判断io_service对象是否已经停止，或者是通过显式的调用stop，或者是
* 完成所有的工作。如果io_service对象已经停止，所有调用run、run_one、poll、poll_one
* 会立即返回，不会调用任何处理句柄。
* @return @c true if the io_service object is stopped, otherwise @c false.
*/
BOOST_ASIO_DECL bool stopped() const;
/// Reset the io_service in preparation for a subsequent run() invocation.
// 为准备后续run函数的调用而重置io_service。
/**
* 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. After a call to reset(), the
* io_service object's stopped() function will return @c false.
* 如果run、run_one、poll、poll_one这些函数由于io_service被停止或者完成任务而返回，
* 我们想再次调用这些函数时，必须首先调用reset函数，再去调用前面的四个函数。调用reset
* 函数后， stopped函数会返回false。
*
* This function must not be called while there are any unfinished calls to
* the run(), run_one(), poll() or poll_one() functions.
* 如果run、run_one、poll、poll_one这些函数中的任何一个没有完成调用，reset函数就不能
* 被调用，否则会出现未定义行为。
*
*/
BOOST_ASIO_DECL 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.
* dispatch函数请求io_service去执行一个给定的处理句柄。
*
* 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.
* io_service保证这个处理句柄仅仅在一个进程中调用，这个进程正在调用run、run_one、poll、poll_one函数。
* 如果满足保证条件，这个句柄会在dispatch这个函数中调用。
*
* @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
* 参数handler是一个被调用的处理句柄，其函数签名必须是void(void)。io_service会复制
* handler对象。
*
* @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.
* 注意：这个函数只会在asio_handler_allocate函数或handler的拷贝构造函数中抛出异常。
*
*/
template <typename CompletionHandler>
BOOST_ASIO_INITFN_RESULT_TYPE(CompletionHandler, void ())
dispatch(BOOST_ASIO_MOVE_ARG(CompletionHandler) handler);
/// Request the io_service to invoke the given handler and return immediately.
/// 请求io_service去执行一个给定的处理句柄并立即返回。
/**
* 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.
* post函数请求io_service去执行一个给定的处理句柄，但是不允许io_service在这个
* 函数中调用处理句柄。
*
* 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.
* io_service保证这个处理句柄仅仅在一个进程中调用，这个进程正在调用run、run_one、
* poll、poll_one函数。
*
* @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
* 参数handler是一个被调用的处理句柄，其函数签名必须是void(void)。io_service会复制
* handler对象。
*
* @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.
* 注意：这个函数只会在asio_handler_allocate函数或handler的拷贝构造函数中抛出异常。
*
*/
template <typename CompletionHandler>
BOOST_ASIO_INITFN_RESULT_TYPE(CompletionHandler, void ())
post(BOOST_ASIO_MOVE_ARG(CompletionHandler) handler);
/// Create a new handler that automatically dispatches the wrapped handler
/// on the io_service.
/// 创建一个新句柄，并自动的分发这个被包装的句柄。
/**
* 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.
* wrap函数创建一个新的句柄对象，在调用时，会自动的把这个被包装的句柄传递给io_service的dispatch函数
* 注：这里好像有错误，需要调用wrapped_handler的重载操作符()，不然这个句柄就不会被调用。
*
* @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
* 参数handler是被包装的句柄，io_service会复制handler对象，handler的函数签名必须
* 是void handler(A1 a1, ... An an)
*
* @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
* 返回一个函数对象，当调用时，把这个包装过得处理句柄传递给io_service的dispatch函数。
* 给一个函数对象其签名是R f(A1 a1, ...An an);
* 当执行：io_service.wrap(f)时
* 返回一个函数对象g，其函数签名是：void g(A1 a1, ...An an)
* 当被调用时，等于执行如下代码：io_service.dispatch(boost::bind(f, a1, ... an));
*
*/
template <typename Handler>
#if defined(GENERATING_DOCUMENTATION)
unspecified
#else
detail::wrapped_handler<io_service&, Handler>
#endif
wrap(Handler handler);
/// Fork-related event notifications.
///fork事件相关的通知
enum fork_event
{
/// Notify the io_service that the process is about to fork.
fork_prepare,
/// Notify the io_service that the process has forked and is the parent.
fork_parent,
/// Notify the io_service that the process has forked and is the child.
fork_child
};
/// Notify the io_service of a fork-related event.
/**
* This function is used to inform the io_service that the process is about
* to fork, or has just forked. This allows the io_service, and the services
* it contains, to perform any necessary housekeeping to ensure correct
* operation following a fork.
*
* This function must not be called while any other io_service function, or
* any function on an I/O object associated with the io_service, is being
* called in another thread. It is, however, safe to call this function from
* within a completion handler, provided no other thread is accessing the
* io_service.
*
* @param event A fork-related event.
*
* @throws boost::system::system_error Thrown on failure. If the notification
* fails the io_service object should no longer be used and should be
* destroyed.
*
* @par Example
* The following code illustrates how to incorporate the notify_fork()
* function:
* @code my_io_service.notify_fork(boost::asio::io_service::fork_prepare);
* if (fork() == 0)
* {
* // This is the child process.
* my_io_service.notify_fork(boost::asio::io_service::fork_child);
* }
* else
* {
* // This is the parent process.
* my_io_service.notify_fork(boost::asio::io_service::fork_parent);
* } @endcode
*
* @note For each service object @c svc in the io_service set, performs
* <tt>svc->fork_service();</tt>. When processing the fork_prepare event,
* services are visited in reverse order of the beginning of service object
* lifetime. Otherwise, services are visited in order of the beginning of
* service object lifetime.
*/
BOOST_ASIO_DECL void notify_fork(boost::asio::io_service::fork_event event);
/// 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.
* particular service with the function template @c has_service<Service>().
* 通过调用use_service，类型参数选择一个Service，这种类型的所有成员就可以使用了。
* 如果Service不在一个io_service，就会创建一个type的Service，并把这个Service加入到io_service。
* 在c++程序中，我们可以用has_service来检查一个io_service对象是否存在一个特殊的service。
*
*/
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.
* add_service函数：在io_service增加一个servcie
*
* @param ios The io_service object that owns the service.
* 参数ios对象拥有这个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.
* Service 对象可以通过add_service加入io_service对象中，加入这个Service对象已经存在，
* 会抛出一个service已经存在的异常。 如果service的拥有者不和参数io_service是同一个对象，
* 会抛出无效的service拥有者的异常。
*
*/
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_ASIO_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_;
};
http://blog.csdn.net/xiaoliangsky/article/details/43125525
测试用例
test_io_service.h
boost::mutex g_mutex;
template<int N>
struct print_n_msg
{
typedef void result_type;
void operator()(const std::string& msg, int flag)
{
boost::mutex::scoped_lock lock(g_mutex);
std::cout << "thread: [" << boost::this_thread::get_id() << "] the num: " << N << " the message is: " << msg << std::endl;
}
void operator()(unsigned int milliseconds, int flag)
{
{
boost::mutex::scoped_lock lock(g_mutex);
std::cout << "thread: [" << boost::this_thread::get_id() << "] sleep begin; the num is: " << N << std::endl;
}
boost::this_thread::sleep(boost::posix_time::milliseconds(milliseconds));
{
boost::mutex::scoped_lock lock(g_mutex);
std::cout << "thread: [" << boost::this_thread::get_id() << "] sleep over." << N << std::endl;;
}
}
void print(const std::string& msg)
{
boost::mutex::scoped_lock lock(g_mutex);
std::cout << "thread: [" << boost::this_thread::get_id() << "] the num: " << N << " the message is: " << msg << std::endl;
}
void operator()(const boost::system::error_code& error)
{
if (!error)
{
boost::mutex::scoped_lock lock(g_mutex);
std::cout << "thread: [" << boost::this_thread::get_id() << "] the num is: " << N << ", no error," << std::endl;
}
else
{
boost::mutex::scoped_lock lock(g_mutex);
std::cout << __FUNCTION__ << " the num is :" << N << " occur a error : " << error.message() << std::endl;
}
}
};
void test_dispatch()
{
boost::asio::io_service io;
boost::asio::deadline_timer t(io);
t.expires_from_now(boost::posix_time::seconds(2));
t.async_wait(print_n_msg<1>());
io.dispatch(boost::bind(print_n_msg<2>(), "dispatch is testing", 1));
io.dispatch(boost::bind(print_n_msg<3>(), 500, 1));
io.run();
}
void bind_run(boost::asio::io_service* io)
{
{
boost::mutex::scoped_lock lock(g_mutex);
std::cout << "thread {{" << boost::this_thread::get_id() << "}} run begin;" << std::endl;
}
size_t rh = io->run();
{
boost::mutex::scoped_lock lock(g_mutex);
std::cout << "thread {{" << boost::this_thread::get_id() << "}} run over;"
<< "the handler number is " << rh << std::endl;
}
}
void test_post()
{
boost::asio::io_service io;
boost::asio::deadline_timer t(io);
t.expires_from_now(boost::posix_time::milliseconds(1));
t.async_wait(boost::bind(print_n_msg<4>(), "wait 4 is finish", 1));
t.async_wait(boost::bind(print_n_msg<5>(), "wait 5 is finish", 1));
t.async_wait(boost::bind(print_n_msg<6>(), "wait 6 is finish", 1));
io.post(boost::bind(print_n_msg<7>(), "post 7 is posted", 1));
io.post(boost::bind(print_n_msg<8>(), "post 8 is posted", 1));
io.post(boost::bind(print_n_msg<9>(), 1, 1));
io.post(boost::bind(print_n_msg<10>(), "post 10 is posted", 1));
io.post(boost::bind(print_n_msg<11>(), 1, 1));
io.post(boost::bind(print_n_msg<12>(), "post 12 is posted", 1));
io.post(boost::bind(print_n_msg<13>(), "post 13 is posted", 1));
boost::thread_group tg;
tg.create_thread(boost::bind(bind_run, &io));
tg.create_thread(boost::bind(bind_run, &io));
tg.join_all();
if (io.stopped())
{
io.reset();
io.post(boost::bind(print_n_msg<14>(), "post 14 is posted", 1));
io.post(boost::bind(print_n_msg<15>(), "post 15 is posted", 1));
io.wrap(boost::bind(print_n_msg<16>(), "post 16 is posted", 1));
io.run();
if (io.stopped())
{
std::cout << "io service is stopped" << std::endl;
}
else
{
std::cout << "no" << std::endl;
}
}
}
void bind_poll(boost::asio::io_service* io)
{
{
boost::mutex::scoped_lock lock(g_mutex);
std::cout << "thread {{" << boost::this_thread::get_id() << "}} poll begin;" << std::endl;
}
size_t rh = io->poll();
{
boost::mutex::scoped_lock lock(g_mutex);
std::cout << "thread {{" << boost::this_thread::get_id() << "}} poll over;"
<< "the handler number is " << rh << std::endl;
}
}
void test_poll()
{
boost::asio::io_service io;
boost::asio::deadline_timer t(io);
t.expires_from_now(boost::posix_time::milliseconds(1));
t.async_wait(boost::bind(print_n_msg<4>(), "wait 4 is finish", 1));
t.async_wait(boost::bind(print_n_msg<5>(), "wait 5 is finish", 1));
t.async_wait(boost::bind(print_n_msg<6>(), "wait 6 is finish", 1));
io.post(boost::bind(print_n_msg<7>(), "post 7 is posted", 1));
io.post(boost::bind(print_n_msg<8>(), "post 8 is posted", 1));
io.post(boost::bind(print_n_msg<9>(), 1, 1));
io.post(boost::bind(print_n_msg<10>(), "post 10 is posted", 1));
io.post(boost::bind(print_n_msg<11>(), 1, 1));
io.post(boost::bind(print_n_msg<12>(), "post 12 is posted", 1));
io.post(boost::bind(print_n_msg<13>(), "post 13 is posted", 1));
boost::thread_group tg;
tg.create_thread(boost::bind(bind_poll, &io));
tg.create_thread(boost::bind(bind_poll, &io));
tg.join_all();
if (io.stopped())
{
io.reset();
io.post(boost::bind(print_n_msg<14>(), "post 14 is posted", 1));
io.post(boost::bind(print_n_msg<15>(), "post 15 is posted", 1));
io.poll();
if (io.stopped())
{
std::cout << "io service is stopped" << std::endl;
}
else
{
std::cout << "no" << std::endl;
}
}
}
//#include <boost/asio/detail/wrapped_handler.hpp>
void test_poll_one()
{
boost::asio::io_service io;
io.post(boost::bind(print_n_msg<7>(), "post 7 is posted", 1));
io.post(boost::bind(print_n_msg<8>(), "post 8 is posted", 1));
io.poll_one();
if (io.stopped())
{
std::cout << "io_service has stopped" << std::endl;
}
else
{
std::cout << "no" << std::endl;
io.poll_one();
if (io.stopped())
{
std::cout << "reset" << std::endl;
io.reset();//这里需要重新启动
boost::function<void(void)> fun = boost::bind(print_n_msg<9>(), "post 9 is posted", 1);
boost::asio::detail::wrapped_handler<boost::asio::io_service&, boost::function<void(void)>>
handler = io.wrap(fun);
handler();//需要自己调用才能执行handler。
io.poll_one();
}
}
}#include "test_io_service.h"
void testIOS()
{
//using namespace stmlIOS;
//test_dispatch();
//test_post();
//std::cout << "\n\n";
//test_poll();
test_poll_one();
}
int main()
{
testIOS();
system("pause");
return 0;
}