strand_service.hpp
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//
// detail/impl/strand_service.hpp
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2020 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 ASIO_DETAIL_IMPL_STRAND_SERVICE_HPP
#define ASIO_DETAIL_IMPL_STRAND_SERVICE_HPP
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
#include "asio/detail/call_stack.hpp"
#include "asio/detail/completion_handler.hpp"
#include "asio/detail/fenced_block.hpp"
#include "asio/detail/handler_alloc_helpers.hpp"
#include "asio/detail/handler_invoke_helpers.hpp"
#include "asio/detail/memory.hpp"
#include "asio/detail/push_options.hpp"
namespace asio {
namespace detail {
inline strand_service::strand_impl::strand_impl()
: operation(&strand_service::do_complete),
locked_(false)
{
}
struct strand_service::on_dispatch_exit
{
io_context_impl* io_context_impl_;
strand_impl* impl_;
~on_dispatch_exit()
{
impl_->mutex_.lock();
impl_->ready_queue_.push(impl_->waiting_queue_);
bool more_handlers = impl_->locked_ = !impl_->ready_queue_.empty();
impl_->mutex_.unlock();
if (more_handlers)
io_context_impl_->post_immediate_completion(impl_, false);
}
};
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))
{
fenced_block b(fenced_block::full);
asio_handler_invoke_helpers::invoke(handler, handler);
return;
}
// Allocate and construct an operation to wrap the handler.
typedef completion_handler<Handler, io_context::executor_type> op;
typename op::ptr p = { asio::detail::addressof(handler),
op::ptr::allocate(handler), 0 };
p.p = new (p.v) op(handler, io_context_.get_executor());
ASIO_HANDLER_CREATION((this->context(),
*p.p, "strand", impl, 0, "dispatch"));
bool dispatch_immediately = do_dispatch(impl, p.p);
operation* o = p.p;
p.v = p.p = 0;
if (dispatch_immediately)
{
// 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_context_impl_, impl };
(void)on_exit;
op::do_complete(&io_context_impl_, o, asio::error_code(), 0);
}
}
// Request the io_context to invoke the given handler and return immediately.
template <typename Handler>
void strand_service::post(strand_service::implementation_type& impl,
Handler& handler)
{
bool is_continuation =
asio_handler_cont_helpers::is_continuation(handler);
// Allocate and construct an operation to wrap the handler.
typedef completion_handler<Handler, io_context::executor_type> op;
typename op::ptr p = { asio::detail::addressof(handler),
op::ptr::allocate(handler), 0 };
p.p = new (p.v) op(handler, io_context_.get_executor());
ASIO_HANDLER_CREATION((this->context(),
*p.p, "strand", impl, 0, "post"));
do_post(impl, p.p, is_continuation);
p.v = p.p = 0;
}
} // namespace detail
} // namespace asio
#include "asio/detail/pop_options.hpp"
#endif // ASIO_DETAIL_IMPL_STRAND_SERVICE_HPP