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//
// io_context.hpp
// ~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2019 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_CONTEXT_HPP
#define BOOST_ASIO_IO_CONTEXT_HPP
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
#include <boost/asio/detail/config.hpp>
#include <cstddef>
#include <stdexcept>
#include <typeinfo>
#include <boost/asio/async_result.hpp>
#include <boost/asio/detail/noncopyable.hpp>
#include <boost/asio/detail/wrapped_handler.hpp>
#include <boost/system/error_code.hpp>
#include <boost/asio/execution_context.hpp>
#if defined(BOOST_ASIO_HAS_CHRONO)
# include <boost/asio/detail/chrono.hpp>
#endif // defined(BOOST_ASIO_HAS_CHRONO)
#if defined(BOOST_ASIO_WINDOWS) || defined(__CYGWIN__)
# include <boost/asio/detail/winsock_init.hpp>
#elif defined(__sun) || defined(__QNX__) || defined(__hpux) || defined(_AIX) \
|| defined(__osf__)
# include <boost/asio/detail/signal_init.hpp>
#endif
#include <boost/asio/detail/push_options.hpp>
namespace boost {
namespace asio {
namespace detail {
#if defined(BOOST_ASIO_HAS_IOCP)
typedef class win_iocp_io_context io_context_impl;
class win_iocp_overlapped_ptr;
#else
typedef class scheduler io_context_impl;
#endif
} // namespace detail
/// Provides core I/O functionality.
/**
* The io_context 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_context 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 restart()
* and notify_fork() functions. Calling restart() while there are unfinished
* run(), run_one(), run_for(), run_until(), poll() or poll_one() calls results
* in undefined behaviour. The notify_fork() function should not be called
* while any io_context function, or any function on an I/O object that is
* associated with the io_context, is being called in another thread.
*
* @par Concepts:
* Dispatcher.
*
* @par Synchronous and asynchronous operations
*
* Synchronous operations on I/O objects implicitly run the io_context object
* for an individual operation. The io_context functions run(), run_one(),
* run_for(), run_until(), poll() or poll_one() must be called for the
* io_context 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(), run_for(),
* run_until(), poll() or poll_one() for the io_context.
*
* @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(),
* run_for(), run_until(), 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(), run_for(),
* run_until(), poll() or poll_one() call may be restarted @em without the need
* for an intervening call to restart(). This allows the thread to rejoin the
* io_context object's thread pool without impacting any other threads in the
* pool.
*
* For example:
*
* @code
* boost::asio::io_context io_context;
* ...
* for (;;)
* {
* try
* {
* io_context.run();
* break; // run() exited normally
* }
* catch (my_exception& e)
* {
* // Deal with exception as appropriate.
* }
* }
* @endcode
*
* @par Submitting arbitrary tasks to the io_context
*
* To submit functions to the io_context, use the @ref boost::asio::dispatch,
* @ref boost::asio::post or @ref boost::asio::defer free functions.
*
* For example:
*
* @code void my_task()
* {
* ...
* }
*
* ...
*
* boost::asio::io_context io_context;
*
* // Submit a function to the io_context.
* boost::asio::post(io_context, my_task);
*
* // Submit a lambda object to the io_context.
* boost::asio::post(io_context,
* []()
* {
* ...
* });
*
* // Run the io_context until it runs out of work.
* io_context.run(); @endcode
*
* @par Stopping the io_context from running out of work
*
* Some applications may need to prevent an io_context object's run() call from
* returning when there is no more work to do. For example, the io_context 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::executor_work_guard<io_context::executor_type>:
*
* @code boost::asio::io_context io_context;
* boost::asio::executor_work_guard<boost::asio::io_context::executor_type>
* = boost::asio::make_work_guard(io_context);
* ... @endcode
*
* To effect a shutdown, the application will then need to call the io_context
* object's stop() member function. This will cause the io_context 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 reset.
*
* @code boost::asio::io_context io_context;
* boost::asio::executor_work_guard<boost::asio::io_context::executor_type>
* = boost::asio::make_work_guard(io_context);
* ...
* work.reset(); // Allow run() to exit. @endcode
*/
class io_context
: public execution_context
{
private:
typedef detail::io_context_impl impl_type;
#if defined(BOOST_ASIO_HAS_IOCP)
friend class detail::win_iocp_overlapped_ptr;
#endif
public:
class executor_type;
friend class executor_type;
#if !defined(BOOST_ASIO_NO_DEPRECATED)
class work;
friend class work;
#endif // !defined(BOOST_ASIO_NO_DEPRECATED)
class service;
#if !defined(BOOST_ASIO_NO_EXTENSIONS)
class strand;
#endif // !defined(BOOST_ASIO_NO_EXTENSIONS)
/// The type used to count the number of handlers executed by the context.
typedef std::size_t count_type;
/// Constructor.
BOOST_ASIO_DECL io_context();
/// 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.
*/
BOOST_ASIO_DECL explicit io_context(int concurrency_hint);
/// Destructor.
/**
* On destruction, the io_context performs the following sequence of
* operations:
*
* @li For each service object @c svc in the io_context set, in reverse order
* of the beginning of service object lifetime, performs
* @c svc->shutdown().
*
* @li Uninvoked handler objects that were scheduled for deferred invocation
* on the io_context, or any associated strand, are destroyed.
*
* @li For each service object @c svc in the io_context set, in reverse order
* of the beginning of service object lifetime, performs
* <tt>delete static_cast<io_context::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_context function stop() is
* called to terminate any run() calls as soon as possible. The io_context
* destructor defined above destroys all handlers, causing all @c shared_ptr
* references to all connection objects to be destroyed.
*/
BOOST_ASIO_DECL ~io_context();
/// Obtains the executor associated with the io_context.
executor_type get_executor() BOOST_ASIO_NOEXCEPT;
/// Run the io_context 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_context has been stopped.
*
* Multiple threads may call the run() function to set up a pool of threads
* from which the io_context may execute handlers. All threads that are
* waiting in the pool are equivalent and the io_context may choose any one
* of them to invoke a handler.
*
* A normal exit from the run() function implies that the io_context 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 restart().
*
* @return The number of handlers that were executed.
*
* @note Calling the run() function from a thread that is currently calling
* one of run(), run_one(), run_for(), run_until(), poll() or poll_one() on
* the same io_context object may introduce the potential for deadlock. It is
* the caller's reponsibility to avoid this.
*
* The poll() function may also be used to dispatch ready handlers, but
* without blocking.
*/
BOOST_ASIO_DECL count_type run();
#if !defined(BOOST_ASIO_NO_DEPRECATED)
/// (Deprecated: Use non-error_code overload.) Run the io_context 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_context has been stopped.
*
* Multiple threads may call the run() function to set up a pool of threads
* from which the io_context may execute handlers. All threads that are
* waiting in the pool are equivalent and the io_context may choose any one
* of them to invoke a handler.
*
* A normal exit from the run() function implies that the io_context 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 restart().
*
* @param ec Set to indicate what error occurred, if any.
*
* @return The number of handlers that were executed.
*
* @note Calling the run() function from a thread that is currently calling
* one of run(), run_one(), run_for(), run_until(), poll() or poll_one() on
* the same io_context object may introduce the potential for deadlock. It is
* the caller's reponsibility to avoid this.
*
* The poll() function may also be used to dispatch ready handlers, but
* without blocking.
*/
BOOST_ASIO_DECL count_type run(boost::system::error_code& ec);
#endif // !defined(BOOST_ASIO_NO_DEPRECATED)
#if defined(BOOST_ASIO_HAS_CHRONO) || defined(GENERATING_DOCUMENTATION)
/// Run the io_context object's event processing loop for a specified
/// duration.
/**
* The run_for() function blocks until all work has finished and there are no
* more handlers to be dispatched, until the io_context has been stopped, or
* until the specified duration has elapsed.
*
* @param rel_time The duration for which the call may block.
*
* @return The number of handlers that were executed.
*/
template <typename Rep, typename Period>
std::size_t run_for(const chrono::duration<Rep, Period>& rel_time);
/// Run the io_context object's event processing loop until a specified time.
/**
* The run_until() function blocks until all work has finished and there are
* no more handlers to be dispatched, until the io_context has been stopped,
* or until the specified time has been reached.
*
* @param abs_time The time point until which the call may block.
*
* @return The number of handlers that were executed.
*/
template <typename Clock, typename Duration>
std::size_t run_until(const chrono::time_point<Clock, Duration>& abs_time);
#endif // defined(BOOST_ASIO_HAS_CHRONO) || defined(GENERATING_DOCUMENTATION)
/// Run the io_context 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_context has been stopped.
*
* @return The number of handlers that were executed. A zero return value
* implies that the io_context 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
* restart().
*
* @note Calling the run_one() function from a thread that is currently
* calling one of run(), run_one(), run_for(), run_until(), poll() or
* poll_one() on the same io_context object may introduce the potential for
* deadlock. It is the caller's reponsibility to avoid this.
*/
BOOST_ASIO_DECL count_type run_one();
#if !defined(BOOST_ASIO_NO_DEPRECATED)
/// (Deprecated: Use non-error_code overlaod.) Run the io_context 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_context has been stopped.
*
* @return The number of handlers that were executed. A zero return value
* implies that the io_context 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
* restart().
*
* @return The number of handlers that were executed.
*
* @note Calling the run_one() function from a thread that is currently
* calling one of run(), run_one(), run_for(), run_until(), poll() or
* poll_one() on the same io_context object may introduce the potential for
* deadlock. It is the caller's reponsibility to avoid this.
*/
BOOST_ASIO_DECL count_type run_one(boost::system::error_code& ec);
#endif // !defined(BOOST_ASIO_NO_DEPRECATED)
#if defined(BOOST_ASIO_HAS_CHRONO) || defined(GENERATING_DOCUMENTATION)
/// Run the io_context object's event processing loop for a specified duration
/// to execute at most one handler.
/**
* The run_one_for() function blocks until one handler has been dispatched,
* until the io_context has been stopped, or until the specified duration has
* elapsed.
*
* @param rel_time The duration for which the call may block.
*
* @return The number of handlers that were executed.
*/
template <typename Rep, typename Period>
std::size_t run_one_for(const chrono::duration<Rep, Period>& rel_time);
/// Run the io_context object's event processing loop until a specified time
/// to execute at most one handler.
/**
* The run_one_until() function blocks until one handler has been dispatched,
* until the io_context has been stopped, or until the specified time has
* been reached.
*
* @param abs_time The time point until which the call may block.
*
* @return The number of handlers that were executed.
*/
template <typename Clock, typename Duration>
std::size_t run_one_until(
const chrono::time_point<Clock, Duration>& abs_time);
#endif // defined(BOOST_ASIO_HAS_CHRONO) || defined(GENERATING_DOCUMENTATION)
/// Run the io_context object's event processing loop to execute ready
/// handlers.
/**
* The poll() function runs handlers that are ready to run, without blocking,
* until the io_context has been stopped or there are no more ready handlers.
*
* @return The number of handlers that were executed.
*/
BOOST_ASIO_DECL count_type poll();
#if !defined(BOOST_ASIO_NO_DEPRECATED)
/// (Deprecated: Use non-error_code overload.) Run the io_context object's
/// event processing loop to execute ready handlers.
/**
* The poll() function runs handlers that are ready to run, without blocking,
* until the io_context 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.
*/
BOOST_ASIO_DECL count_type poll(boost::system::error_code& ec);
#endif // !defined(BOOST_ASIO_NO_DEPRECATED)
/// Run the io_context 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.
*/
BOOST_ASIO_DECL count_type poll_one();
#if !defined(BOOST_ASIO_NO_DEPRECATED)
/// (Deprecated: Use non-error_code overload.) Run the io_context 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 count_type poll_one(boost::system::error_code& ec);
#endif // !defined(BOOST_ASIO_NO_DEPRECATED)
/// Stop the io_context object's event processing loop.
/**
* This function does not block, but instead simply signals the io_context 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 restart() is called.
*/
BOOST_ASIO_DECL void stop();
/// Determine whether the io_context object has been stopped.
/**
* This function is used to determine whether an io_context object has been
* stopped, either through an explicit call to stop(), or due to running out
* of work. When an io_context object is stopped, calls to run(), run_one(),
* poll() or poll_one() will return immediately without invoking any
* handlers.
*
* @return @c true if the io_context object is stopped, otherwise @c false.
*/
BOOST_ASIO_DECL bool stopped() const;
/// Restart the io_context 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_context
* being stopped or running out of work. After a call to restart(), the
* io_context object's stopped() function will return @c false.
*
* This function must not be called while there are any unfinished calls to
* the run(), run_one(), poll() or poll_one() functions.
*/
BOOST_ASIO_DECL void restart();
#if !defined(BOOST_ASIO_NO_DEPRECATED)
/// (Deprecated: Use restart().) Reset the io_context 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_context
* being stopped or running out of work. After a call to restart(), the
* io_context object's stopped() function will return @c false.
*
* This function must not be called while there are any unfinished calls to
* the run(), run_one(), poll() or poll_one() functions.
*/
void reset();
/// (Deprecated: Use boost::asio::dispatch().) Request the io_context to
/// invoke the given handler.
/**
* This function is used to ask the io_context to execute the given handler.
*
* The io_context 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_context 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 LegacyCompletionHandler>
BOOST_ASIO_INITFN_AUTO_RESULT_TYPE(LegacyCompletionHandler, void ())
dispatch(BOOST_ASIO_MOVE_ARG(LegacyCompletionHandler) handler);
/// (Deprecated: Use boost::asio::post().) Request the io_context to invoke
/// the given handler and return immediately.
/**
* This function is used to ask the io_context to execute the given handler,
* but without allowing the io_context to call the handler from inside this
* function.
*
* The io_context 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_context 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 LegacyCompletionHandler>
BOOST_ASIO_INITFN_AUTO_RESULT_TYPE(LegacyCompletionHandler, void ())
post(BOOST_ASIO_MOVE_ARG(LegacyCompletionHandler) handler);
/// (Deprecated: Use boost::asio::bind_executor().) Create a new handler that
/// automatically dispatches the wrapped handler on the io_context.
/**
* This function is used to create a new handler function object that, when
* invoked, will automatically pass the wrapped handler to the io_context
* object's dispatch function.
*
* @param handler The handler to be wrapped. The io_context 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_context 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_context.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_context.dispatch(boost::bind(f, a1, ... an)); @endcode
*/
template <typename Handler>
#if defined(GENERATING_DOCUMENTATION)
unspecified
#else
detail::wrapped_handler<io_context&, Handler>
#endif
wrap(Handler handler);
#endif // !defined(BOOST_ASIO_NO_DEPRECATED)
private:
#if !defined(BOOST_ASIO_NO_DEPRECATED)
struct initiate_dispatch;
struct initiate_post;
#endif // !defined(BOOST_ASIO_NO_DEPRECATED)
// Helper function to add the implementation.
BOOST_ASIO_DECL impl_type& add_impl(impl_type* impl);
// Backwards compatible overload for use with services derived from
// io_context::service.
template <typename Service>
friend Service& use_service(io_context& ioc);
#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 implementation.
impl_type& impl_;
};
/// Executor used to submit functions to an io_context.
class io_context::executor_type
{
public:
/// Obtain the underlying execution context.
io_context& context() const BOOST_ASIO_NOEXCEPT;
/// Inform the io_context that it has some outstanding work to do.
/**
* This function is used to inform the io_context that some work has begun.
* This ensures that the io_context's run() and run_one() functions do not
* exit while the work is underway.
*/
void on_work_started() const BOOST_ASIO_NOEXCEPT;
/// Inform the io_context that some work is no longer outstanding.
/**
* This function is used to inform the io_context that some work has
* finished. Once the count of unfinished work reaches zero, the io_context
* is stopped and the run() and run_one() functions may exit.
*/
void on_work_finished() const BOOST_ASIO_NOEXCEPT;
/// Request the io_context to invoke the given function object.
/**
* This function is used to ask the io_context to execute the given function
* object. If the current thread is running the io_context, @c dispatch()
* executes the function before returning. Otherwise, the function will be
* scheduled to run on the io_context.
*
* @param f The function object to be called. The executor will make a copy
* of the handler object as required. The function signature of the function
* object must be: @code void function(); @endcode
*
* @param a An allocator that may be used by the executor to allocate the
* internal storage needed for function invocation.
*/
template <typename Function, typename Allocator>
void dispatch(BOOST_ASIO_MOVE_ARG(Function) f, const Allocator& a) const;
/// Request the io_context to invoke the given function object.
/**
* This function is used to ask the io_context to execute the given function
* object. The function object will never be executed inside @c post().
* Instead, it will be scheduled to run on the io_context.
*
* @param f The function object to be called. The executor will make a copy
* of the handler object as required. The function signature of the function
* object must be: @code void function(); @endcode
*
* @param a An allocator that may be used by the executor to allocate the
* internal storage needed for function invocation.
*/
template <typename Function, typename Allocator>
void post(BOOST_ASIO_MOVE_ARG(Function) f, const Allocator& a) const;
/// Request the io_context to invoke the given function object.
/**
* This function is used to ask the io_context to execute the given function
* object. The function object will never be executed inside @c defer().
* Instead, it will be scheduled to run on the io_context.
*
* If the current thread belongs to the io_context, @c defer() will delay
* scheduling the function object until the current thread returns control to
* the pool.
*
* @param f The function object to be called. The executor will make a copy
* of the handler object as required. The function signature of the function
* object must be: @code void function(); @endcode
*
* @param a An allocator that may be used by the executor to allocate the
* internal storage needed for function invocation.
*/
template <typename Function, typename Allocator>
void defer(BOOST_ASIO_MOVE_ARG(Function) f, const Allocator& a) const;
/// Determine whether the io_context is running in the current thread.
/**
* @return @c true if the current thread is running the io_context. Otherwise
* returns @c false.
*/
bool running_in_this_thread() const BOOST_ASIO_NOEXCEPT;
/// Compare two executors for equality.
/**
* Two executors are equal if they refer to the same underlying io_context.
*/
friend bool operator==(const executor_type& a,
const executor_type& b) BOOST_ASIO_NOEXCEPT
{
return &a.io_context_ == &b.io_context_;
}
/// Compare two executors for inequality.
/**
* Two executors are equal if they refer to the same underlying io_context.
*/
friend bool operator!=(const executor_type& a,
const executor_type& b) BOOST_ASIO_NOEXCEPT
{
return &a.io_context_ != &b.io_context_;
}
private:
friend class io_context;
// Constructor.
explicit executor_type(io_context& i) : io_context_(i) {}
// The underlying io_context.
io_context& io_context_;
};
#if !defined(BOOST_ASIO_NO_DEPRECATED)
/// (Deprecated: Use executor_work_guard.) Class to inform the io_context when
/// it has work to do.
/**
* The work class is used to inform the io_context when work starts and
* finishes. This ensures that the io_context 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_context::work
{
public:
/// Constructor notifies the io_context that work is starting.
/**
* The constructor is used to inform the io_context that some work has begun.
* This ensures that the io_context object's run() function will not exit
* while the work is underway.
*/
explicit work(boost::asio::io_context& io_context);
/// Copy constructor notifies the io_context that work is starting.
/**
* The constructor is used to inform the io_context that some work has begun.
* This ensures that the io_context object's run() function will not exit
* while the work is underway.
*/
work(const work& other);
/// Destructor notifies the io_context that the work is complete.
/**
* The destructor is used to inform the io_context that some work has
* finished. Once the count of unfinished work reaches zero, the io_context
* object's run() function is permitted to exit.
*/
~work();
/// Get the io_context associated with the work.
boost::asio::io_context& get_io_context();
private:
// Prevent assignment.
void operator=(const work& other);
// The io_context implementation.
detail::io_context_impl& io_context_impl_;
};
#endif // !defined(BOOST_ASIO_NO_DEPRECATED)
/// Base class for all io_context services.
class io_context::service
: public execution_context::service
{
public:
/// Get the io_context object that owns the service.
boost::asio::io_context& get_io_context();
private:
/// Destroy all user-defined handler objects owned by the service.
BOOST_ASIO_DECL virtual void shutdown();
#if !defined(BOOST_ASIO_NO_DEPRECATED)
/// (Deprecated: Use shutdown().) Destroy all user-defined handler objects
/// owned by the service.
BOOST_ASIO_DECL virtual void shutdown_service();
#endif // !defined(BOOST_ASIO_NO_DEPRECATED)
/// Handle notification of a fork-related event to perform any necessary
/// housekeeping.
/**
* This function is not a pure virtual so that services only have to
* implement it if necessary. The default implementation does nothing.
*/
BOOST_ASIO_DECL virtual void notify_fork(
execution_context::fork_event event);
#if !defined(BOOST_ASIO_NO_DEPRECATED)
/// (Deprecated: Use notify_fork().) Handle notification of a fork-related
/// event to perform any necessary housekeeping.
/**
* This function is not a pure virtual so that services only have to
* implement it if necessary. The default implementation does nothing.
*/
BOOST_ASIO_DECL virtual void fork_service(
execution_context::fork_event event);
#endif // !defined(BOOST_ASIO_NO_DEPRECATED)
protected:
/// Constructor.
/**
* @param owner The io_context object that owns the service.
*/
BOOST_ASIO_DECL service(boost::asio::io_context& owner);
/// Destructor.
BOOST_ASIO_DECL virtual ~service();
};
namespace detail {
// Special service base class to keep classes header-file only.
template <typename Type>
class service_base
: public boost::asio::io_context::service
{
public:
static boost::asio::detail::service_id<Type> id;
// Constructor.
service_base(boost::asio::io_context& io_context)
: boost::asio::io_context::service(io_context)
{
}
};
template <typename Type>
boost::asio::detail::service_id<Type> service_base<Type>::id;
} // namespace detail
} // namespace asio
} // namespace boost
#include <boost/asio/detail/pop_options.hpp>
#include <boost/asio/impl/io_context.hpp>
#if defined(BOOST_ASIO_HEADER_ONLY)
# include <boost/asio/impl/io_context.ipp>
#endif // defined(BOOST_ASIO_HEADER_ONLY)
// If both io_context.hpp and strand.hpp have been included, automatically
// include the header file needed for the io_context::strand class.
#if !defined(BOOST_ASIO_NO_EXTENSIONS)
# if defined(BOOST_ASIO_STRAND_HPP)
# include <boost/asio/io_context_strand.hpp>
# endif // defined(BOOST_ASIO_STRAND_HPP)
#endif // !defined(BOOST_ASIO_NO_EXTENSIONS)
#endif // BOOST_ASIO_IO_CONTEXT_HPP