boost/asio/detail/impl/strand_service.hpp

   1 //
   2 // detail/impl/strand_service.hpp
   3 // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   4 //
   5 // Copyright (c) 2003-2014 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 BOOST_ASIO_DETAIL_IMPL_STRAND_SERVICE_HPP
  12 #define BOOST_ASIO_DETAIL_IMPL_STRAND_SERVICE_HPP
  13
  14 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  15 # pragma once
  16 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  17
  18 #include <boost/asio/detail/addressof.hpp>
  19 #include <boost/asio/detail/call_stack.hpp>
  20 #include <boost/asio/detail/completion_handler.hpp>
  21 #include <boost/asio/detail/fenced_block.hpp>
  22 #include <boost/asio/detail/handler_alloc_helpers.hpp>
  23 #include <boost/asio/detail/handler_invoke_helpers.hpp>
  24
  25 #include <boost/asio/detail/push_options.hpp>
  26
  27 namespace boost {
  28 namespace asio {
  29 namespace detail {
  30
  31 inline strand_service::strand_impl::strand_impl()
  32   : operation(&strand_service::do_complete),
  33     locked_(false)
  34 {
  35 }
  36
  37 struct strand_service::on_dispatch_exit
  38 {
  39   io_service_impl* io_service_;
  40   strand_impl* impl_;
  41
  42   ~on_dispatch_exit()
  43   {
  44     impl_->mutex_.lock();
  45     impl_->ready_queue_.push(impl_->waiting_queue_);
  46     bool more_handlers = impl_->locked_ = !impl_->ready_queue_.empty();
  47     impl_->mutex_.unlock();
  48
  49     if (more_handlers)
  50       io_service_->post_immediate_completion(impl_, false);
  51   }
  52 };
  53
  54 template <typename Handler>
  55 void strand_service::dispatch(strand_service::implementation_type& impl,
  56     Handler& handler)
  57 {
  58   // If we are already in the strand then the handler can run immediately.
  59   if (call_stack<strand_impl>::contains(impl))
  60   {
  61     fenced_block b(fenced_block::full);
  62     boost_asio_handler_invoke_helpers::invoke(handler, handler);
  63     return;
  64   }
  65
  66   // Allocate and construct an operation to wrap the handler.
  67   typedef completion_handler<Handler> op;
  68   typename op::ptr p = { boost::asio::detail::addressof(handler),
  69     boost_asio_handler_alloc_helpers::allocate(
  70       sizeof(op), handler), 0 };
  71   p.p = new (p.v) op(handler);
  72
  73   BOOST_ASIO_HANDLER_CREATION((p.p, "strand", impl, "dispatch"));
  74
  75   bool dispatch_immediately = do_dispatch(impl, p.p);
  76   operation* o = p.p;
  77   p.v = p.p = 0;
  78
  79   if (dispatch_immediately)
  80   {
  81     // Indicate that this strand is executing on the current thread.
  82     call_stack<strand_impl>::context ctx(impl);
  83
  84     // Ensure the next handler, if any, is scheduled on block exit.
  85     on_dispatch_exit on_exit = { &io_service_, impl };
  86     (void)on_exit;
  87
  88     completion_handler<Handler>::do_complete(
  89         &io_service_, o, boost::system::error_code(), 0);
  90   }
  91 }
  92
  93 // Request the io_service to invoke the given handler and return immediately.
  94 template <typename Handler>
  95 void strand_service::post(strand_service::implementation_type& impl,
  96     Handler& handler)
  97 {
  98   bool is_continuation =
  99     boost_asio_handler_cont_helpers::is_continuation(handler);
 100
 101   // Allocate and construct an operation to wrap the handler.
 102   typedef completion_handler<Handler> op;
 103   typename op::ptr p = { boost::asio::detail::addressof(handler),
 104     boost_asio_handler_alloc_helpers::allocate(
 105       sizeof(op), handler), 0 };
 106   p.p = new (p.v) op(handler);
 107
 108   BOOST_ASIO_HANDLER_CREATION((p.p, "strand", impl, "post"));
 109
 110   do_post(impl, p.p, is_continuation);
 111   p.v = p.p = 0;
 112 }
 113
 114 } // namespace detail
 115 } // namespace asio
 116 } // namespace boost
 117
 118 #include <boost/asio/detail/pop_options.hpp>
 119
 120 #endif // BOOST_ASIO_DETAIL_IMPL_STRAND_SERVICE_HPP