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//
// detail/impl/strand_service.hpp
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2011 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_DETAIL_IMPL_STRAND_SERVICE_HPP
#define BOOST_ASIO_DETAIL_IMPL_STRAND_SERVICE_HPP
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
#include <boost/asio/detail/call_stack.hpp>
#include <boost/asio/detail/completion_handler.hpp>
#include <boost/asio/detail/fenced_block.hpp>
#include <boost/asio/detail/handler_alloc_helpers.hpp>
#include <boost/asio/detail/handler_invoke_helpers.hpp>
#include <boost/asio/detail/push_options.hpp>
namespace boost {
namespace asio {
namespace detail {
inline strand_service::strand_impl::strand_impl()
: operation(&strand_service::do_complete),
count_(0)
{
}
struct strand_service::on_dispatch_exit
{
io_service_impl* io_service_;
strand_impl* impl_;
~on_dispatch_exit()
{
impl_->mutex_.lock();
bool more_handlers = (--impl_->count_ > 0);
impl_->mutex_.unlock();
if (more_handlers)
io_service_->post_immediate_completion(impl_);
}
};
inline void strand_service::destroy(strand_service::implementation_type& impl)
{
impl = 0;
}
template <typename Handler>
void strand_service::dispatch(strand_service::implementation_type& impl,
Handler handler)
{
// If we are already in the strand then the handler can run immediately.
if (call_stack<strand_impl>::contains(impl))
{
boost::asio::detail::fenced_block b;
boost_asio_handler_invoke_helpers::invoke(handler, handler);
return;
}
// Allocate and construct an operation to wrap the handler.
typedef completion_handler<Handler> op;
typename op::ptr p = { boost::addressof(handler),
boost_asio_handler_alloc_helpers::allocate(
sizeof(op), handler), 0 };
p.p = new (p.v) op(handler);
// If we are running inside the io_service, and no other handler is queued
// or running, then the handler can run immediately.
bool can_dispatch = call_stack<io_service_impl>::contains(&io_service_);
impl->mutex_.lock();
bool first = (++impl->count_ == 1);
if (can_dispatch && first)
{
// Immediate invocation is allowed.
impl->mutex_.unlock();
// Memory must be releaesed before any upcall is made.
p.reset();
// Indicate that this strand is executing on the current thread.
call_stack<strand_impl>::context ctx(impl);
// Ensure the next handler, if any, is scheduled on block exit.
on_dispatch_exit on_exit = { &io_service_, impl };
(void)on_exit;
boost::asio::detail::fenced_block b;
boost_asio_handler_invoke_helpers::invoke(handler, handler);
return;
}
// Immediate invocation is not allowed, so enqueue for later.
impl->queue_.push(p.p);
impl->mutex_.unlock();
p.v = p.p = 0;
// The first handler to be enqueued is responsible for scheduling the
// strand.
if (first)
io_service_.post_immediate_completion(impl);
}
// Request the io_service to invoke the given handler and return immediately.
template <typename Handler>
void strand_service::post(strand_service::implementation_type& impl,
Handler handler)
{
// Allocate and construct an operation to wrap the handler.
typedef completion_handler<Handler> op;
typename op::ptr p = { boost::addressof(handler),
boost_asio_handler_alloc_helpers::allocate(
sizeof(op), handler), 0 };
p.p = new (p.v) op(handler);
// Add the handler to the queue.
impl->mutex_.lock();
bool first = (++impl->count_ == 1);
impl->queue_.push(p.p);
impl->mutex_.unlock();
p.v = p.p = 0;
// The first handler to be enqueue is responsible for scheduling the strand.
if (first)
io_service_.post_immediate_completion(impl);
}
} // namespace detail
} // namespace asio
} // namespace boost
#include <boost/asio/detail/pop_options.hpp>
#endif // BOOST_ASIO_DETAIL_IMPL_STRAND_SERVICE_HPP
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