beast/core/bind_handler.hpp

0001 //
0002 // Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com)
0003 //
0004 // Distributed under the Boost Software License, Version 1.0. (See accompanying
0005 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0006 //
0007 // Official repository: https://github.com/boostorg/beast
0008 //
0009
0010 #ifndef BOOST_BEAST_BIND_HANDLER_HPP
0011 #define BOOST_BEAST_BIND_HANDLER_HPP
0012
0013 #include <boost/beast/core/detail/config.hpp>
0014 #include <boost/beast/core/detail/bind_handler.hpp>
0015 #include <type_traits>
0016 #include <utility>
0017
0018 namespace boost {
0019 namespace beast {
0020
0021 /** Bind parameters to a completion handler, creating a new handler.
0022
0023     This function creates a new handler which, when invoked, calls
0024     the original handler with the list of bound arguments. Any
0025     parameters passed in the invocation will be substituted for
0026     placeholders present in the list of bound arguments. Parameters
0027     which are not matched to placeholders are silently discarded.
0028
0029     The passed handler and arguments are forwarded into the returned
0030     handler, whose associated allocator and associated executor will
0031     be the same as those of the original handler.
0032
0033     @par Example
0034
0035     This function posts the invocation of the specified completion
0036     handler with bound arguments:
0037
0038     @code
0039     template <class AsyncReadStream, class ReadHandler>
0040     void
0041     signal_aborted (AsyncReadStream& stream, ReadHandler&& handler)
0042     {
0043         net::post(
0044             stream.get_executor(),
0045             bind_handler (std::forward <ReadHandler> (handler),
0046                 net::error::operation_aborted, 0));
0047     }
0048     @endcode
0049
0050     @param handler The handler to wrap.
0051     The implementation takes ownership of the handler by performing a decay-copy.
0052
0053     @param args A list of arguments to bind to the handler.
0054     The arguments are forwarded into the returned object. These
0055     arguments may include placeholders, which will operate in
0056     a fashion identical to a call to `std::bind`.
0057 */
0058 template<class Handler, class... Args>
0059 #if BOOST_BEAST_DOXYGEN
0060 __implementation_defined__
0061 #else
0062 detail::bind_wrapper<
0063     typename std::decay<Handler>::type,
0064     typename std::decay<Args>::type...>
0065 #endif
0066 bind_handler(Handler&& handler, Args&&... args)
0067 {
0068     return detail::bind_wrapper<
0069         typename std::decay<Handler>::type,
0070         typename std::decay<Args>::type...>(
0071             std::forward<Handler>(handler),
0072             std::forward<Args>(args)...);
0073 }
0074
0075 /** Bind parameters to a completion handler, creating a new handler.
0076
0077     This function creates a new handler which, when invoked, calls
0078     the original handler with the list of bound arguments. Any
0079     parameters passed in the invocation will be forwarded in
0080     the parameter list after the bound arguments.
0081
0082     The passed handler and arguments are forwarded into the returned
0083     handler, whose associated allocator and associated executor will
0084     will be the same as those of the original handler.
0085
0086     @par Example
0087
0088     This function posts the invocation of the specified completion
0089     handler with bound arguments:
0090
0091     @code
0092     template <class AsyncReadStream, class ReadHandler>
0093     void
0094     signal_eof (AsyncReadStream& stream, ReadHandler&& handler)
0095     {
0096         net::post(
0097             stream.get_executor(),
0098             bind_front_handler (std::forward<ReadHandler> (handler),
0099                 net::error::eof, 0));
0100     }
0101     @endcode
0102
0103     @param handler The handler to wrap.
0104     The implementation takes ownership of the handler by performing a decay-copy.
0105
0106     @param args A list of arguments to bind to the handler.
0107     The arguments are forwarded into the returned object.
0108 */
0109 template<class Handler, class... Args>
0110 #if BOOST_BEAST_DOXYGEN
0111 __implementation_defined__
0112 #else
0113 auto
0114 #endif
0115 bind_front_handler(
0116     Handler&& handler,
0117     Args&&... args) ->
0118     detail::bind_front_wrapper<
0119         typename std::decay<Handler>::type,
0120         typename std::decay<Args>::type...>
0121 {
0122     return detail::bind_front_wrapper<
0123         typename std::decay<Handler>::type,
0124         typename std::decay<Args>::type...>(
0125             std::forward<Handler>(handler),
0126             std::forward<Args>(args)...);
0127 }
0128
0129 } // beast
0130 } // boost
0131
0132 #endif