1 // 2 // handler_invoke_hook.hpp 3 // ~~~~~~~~~~~~~~~~~~~~~~~ 4 // 5 // Copyright (c) 2003-2015 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 ASIO_HANDLER_INVOKE_HOOK_HPP 12 #define ASIO_HANDLER_INVOKE_HOOK_HPP 13 14 15 #include "asio/detail/config.hpp" 16 17 #include "asio/detail/push_options.hpp" 18 19 namespace asio { 20 21 /** @defgroup asio_handler_invoke asio::asio_handler_invoke 22 * 23 * @brief Default invoke function for handlers. 24 * 25 * Completion handlers for asynchronous operations are invoked by the 26 * io_service associated with the corresponding object (e.g. a socket or 27 * deadline_timer). Certain guarantees are made on when the handler may be 28 * invoked, in particular that a handler can only be invoked from a thread that 29 * is currently calling @c run() on the corresponding io_service object. 30 * Handlers may subsequently be invoked through other objects (such as 31 * io_service::strand objects) that provide additional guarantees. 32 * 33 * When asynchronous operations are composed from other asynchronous 34 * operations, all intermediate handlers should be invoked using the same 35 * method as the final handler. This is required to ensure that user-defined 36 * objects are not accessed in a way that may violate the guarantees. This 37 * hooking function ensures that the invoked method used for the final handler 38 * is accessible at each intermediate step. 39 * 40 * Implement asio_handler_invoke for your own handlers to specify a custom 41 * invocation strategy. 42 * 43 * This default implementation invokes the function object like so: 44 * @code function(); @endcode 45 * If necessary, the default implementation makes a copy of the function object 46 * so that the non-const operator() can be used. 47 * 48 * @par Example 49 * @code 50 * class my_handler; 51 * 52 * template <typename Function> 53 * void asio_handler_invoke(Function function, my_handler* context) 54 * { 55 * context->strand_.dispatch(function); 56 * } 57 * @endcode 58 */ 59 /*@{*/ 60 61 /// Default handler invocation hook used for non-const function objects. 62 template <typename Function> 63 inline void asio_handler_invoke(Function& function, ...) 64 { 65 function(); 66 } 67 68 /// Default handler invocation hook used for const function objects. 69 template <typename Function> 70 inline void asio_handler_invoke(const Function& function, ...) 71 { 72 Function tmp(function); 73 tmp(); 74 } 75 76 /*@}*/ 77 78 } // namespace asio 79 80 #include "asio/detail/pop_options.hpp" 81 82 #endif // ASIO_HANDLER_INVOKE_HOOK_HPP 83
