ceph/src/boost/boost/beast/core/bind_handler.hpp

   1 //
   2 // Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail dot com)
   3 //
   4 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   5 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6 //
   7 // Official repository: https://github.com/boostorg/beast
   8 //
   9
  10 #ifndef BOOST_BEAST_BIND_HANDLER_HPP
  11 #define BOOST_BEAST_BIND_HANDLER_HPP
  12
  13 #include <boost/beast/core/detail/config.hpp>
  14 #include <boost/beast/core/type_traits.hpp>
  15 #include <boost/beast/core/detail/bind_handler.hpp>
  16 #include <type_traits>
  17 #include <utility>
  18
  19 namespace boost {
  20 namespace beast {
  21
  22 /** Bind parameters to a completion handler, creating a new handler.
  23
  24     This function creates a new handler which, when invoked, calls
  25     the original handler with the list of bound arguments. Any
  26     parameters passed in the invocation will be subtituted for
  27     placeholders present in the list of bound arguments. Parameters
  28     which are not matched to placeholders are silently discarded.
  29     The passed handler and arguments are forwarded into the returned
  30     handler, which provides the same `io_context` execution guarantees
  31     as the original handler.
  32
  33     Unlike `boost::asio::io_context::wrap`, the returned handler can
  34     be used in a subsequent call to `boost::asio::io_context::post`
  35     instead of `boost::asio::io_context::dispatch`, to ensure that
  36     the handler will not be invoked immediately by the calling
  37     function.
  38
  39     Example:
  40
  41     @code
  42     template<class AsyncReadStream, class ReadHandler>
  43     void
  44     signal_aborted(AsyncReadStream& stream, ReadHandler&& handler)
  45     {
  46         boost::asio::post(
  47             stream.get_executor(),
  48             bind_handler(std::forward<ReadHandler>(handler),
  49                 boost::asio::error::operation_aborted, 0));
  50     }
  51     @endcode
  52
  53     @param handler The handler to wrap.
  54
  55     @param args A list of arguments to bind to the handler. The
  56     arguments are forwarded into the returned object.
  57 */
  58 template<class Handler, class... Args>
  59 #if BOOST_BEAST_DOXYGEN
  60 implementation_defined
  61 #else
  62 detail::bound_handler<
  63     typename std::decay<Handler>::type, Args...>
  64 #endif
  65 bind_handler(Handler&& handler, Args&&... args)
  66 {
  67 #if 0
  68     static_assert(is_completion_handler<
  69         Handler, void(Args...)>::value,
  70             "Handler requirements not met");
  71 #endif
  72     return detail::bound_handler<typename std::decay<
  73         Handler>::type, Args...>(std::forward<
  74             Handler>(handler), std::forward<Args>(args)...);
  75 }
  76
  77 } // beast
  78 } // boost
  79
  80 #endif