//
|
// handler_invoke_hook.hpp
|
// ~~~~~~~~~~~~~~~~~~~~~~~
|
//
|
// Copyright (c) 2003-2020 Christopher M. Kohlhoff (chris at kohlhoff dot com)
|
//
|
// Distributed under the Boost Software License, Version 1.0. (See accompanying
|
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
|
//
|
|
#ifndef BOOST_ASIO_HANDLER_INVOKE_HOOK_HPP
|
#define BOOST_ASIO_HANDLER_INVOKE_HOOK_HPP
|
|
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
|
# pragma once
|
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
|
|
#include <boost/asio/detail/config.hpp>
|
|
#include <boost/asio/detail/push_options.hpp>
|
|
namespace boost {
|
namespace asio {
|
|
/** @defgroup asio_handler_invoke boost::asio::asio_handler_invoke
|
*
|
* @brief (Deprecated: Use the associated_executor trait.) Default invoke
|
* function for handlers.
|
*
|
* Completion handlers for asynchronous operations are invoked by the
|
* io_context associated with the corresponding object (e.g. a socket or
|
* deadline_timer). Certain guarantees are made on when the handler may be
|
* invoked, in particular that a handler can only be invoked from a thread that
|
* is currently calling @c run() on the corresponding io_context object.
|
* Handlers may subsequently be invoked through other objects (such as
|
* io_context::strand objects) that provide additional guarantees.
|
*
|
* When asynchronous operations are composed from other asynchronous
|
* operations, all intermediate handlers should be invoked using the same
|
* method as the final handler. This is required to ensure that user-defined
|
* objects are not accessed in a way that may violate the guarantees. This
|
* hooking function ensures that the invoked method used for the final handler
|
* is accessible at each intermediate step.
|
*
|
* Implement asio_handler_invoke for your own handlers to specify a custom
|
* invocation strategy.
|
*
|
* This default implementation invokes the function object like so:
|
* @code function(); @endcode
|
* If necessary, the default implementation makes a copy of the function object
|
* so that the non-const operator() can be used.
|
*
|
* @par Example
|
* @code
|
* class my_handler;
|
*
|
* template <typename Function>
|
* void asio_handler_invoke(Function function, my_handler* context)
|
* {
|
* context->strand_.dispatch(function);
|
* }
|
* @endcode
|
*/
|
/*@{*/
|
|
#if defined(BOOST_ASIO_NO_DEPRECATED)
|
|
// Places in asio that would have previously called the invocation hook to
|
// execute a handler, now call it only to check whether the result type is this
|
// type. If the result is not this type, it indicates that the user code still
|
// has the old hooks in place, and if so we want to trigger a compile error.
|
enum asio_handler_invoke_is_no_longer_used {};
|
|
typedef asio_handler_invoke_is_no_longer_used
|
asio_handler_invoke_is_deprecated;
|
|
#else // defined(BOOST_ASIO_NO_DEPRECATED)
|
|
typedef void asio_handler_invoke_is_deprecated;
|
|
#endif // defined(BOOST_ASIO_NO_DEPRECATED)
|
|
/// Default handler invocation hook used for non-const function objects.
|
template <typename Function>
|
inline asio_handler_invoke_is_deprecated
|
asio_handler_invoke(Function& function, ...)
|
{
|
function();
|
#if defined(BOOST_ASIO_NO_DEPRECATED)
|
return asio_handler_invoke_is_no_longer_used();
|
#endif // defined(BOOST_ASIO_NO_DEPRECATED)
|
}
|
|
/// Default handler invocation hook used for const function objects.
|
template <typename Function>
|
inline asio_handler_invoke_is_deprecated
|
asio_handler_invoke(const Function& function, ...)
|
{
|
Function tmp(function);
|
tmp();
|
#if defined(BOOST_ASIO_NO_DEPRECATED)
|
return asio_handler_invoke_is_no_longer_used();
|
#endif // defined(BOOST_ASIO_NO_DEPRECATED)
|
}
|
|
/*@}*/
|
|
} // namespace asio
|
} // namespace boost
|
|
#include <boost/asio/detail/pop_options.hpp>
|
|
#endif // BOOST_ASIO_HANDLER_INVOKE_HOOK_HPP
|
