762 lines
20 KiB
C++
Executable File
762 lines
20 KiB
C++
Executable File
//
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// impl/awaitable.hpp
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// ~~~~~~~~~~~~~~~~~~
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//
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// Copyright (c) 2003-2022 Christopher M. Kohlhoff (chris at kohlhoff dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#ifndef BOOST_ASIO_IMPL_AWAITABLE_HPP
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#define BOOST_ASIO_IMPL_AWAITABLE_HPP
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#if defined(_MSC_VER) && (_MSC_VER >= 1200)
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# pragma once
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#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
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#include <boost/asio/detail/config.hpp>
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#include <exception>
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#include <new>
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#include <tuple>
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#include <boost/asio/cancellation_signal.hpp>
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#include <boost/asio/cancellation_state.hpp>
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#include <boost/asio/detail/thread_context.hpp>
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#include <boost/asio/detail/thread_info_base.hpp>
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#include <boost/asio/detail/throw_error.hpp>
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#include <boost/asio/detail/type_traits.hpp>
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#include <boost/asio/error.hpp>
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#include <boost/asio/post.hpp>
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#include <boost/system/system_error.hpp>
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#include <boost/asio/this_coro.hpp>
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#include <boost/asio/detail/push_options.hpp>
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namespace boost {
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namespace asio {
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namespace detail {
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struct awaitable_thread_has_context_switched {};
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// An awaitable_thread represents a thread-of-execution that is composed of one
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// or more "stack frames", with each frame represented by an awaitable_frame.
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// All execution occurs in the context of the awaitable_thread's executor. An
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// awaitable_thread continues to "pump" the stack frames by repeatedly resuming
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// the top stack frame until the stack is empty, or until ownership of the
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// stack is transferred to another awaitable_thread object.
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//
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// +------------------------------------+
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// | top_of_stack_ |
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// | V
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// +--------------+---+ +-----------------+
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// | | | |
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// | awaitable_thread |<---------------------------+ awaitable_frame |
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// | | attached_thread_ | |
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// +--------------+---+ (Set only when +---+-------------+
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// | frames are being |
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// | actively pumped | caller_
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// | by a thread, and |
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// | then only for V
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// | the top frame.) +-----------------+
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// | | |
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// | | awaitable_frame |
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// | | |
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// | +---+-------------+
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// | |
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// | | caller_
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// | :
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// | :
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// | |
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// | V
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// | +-----------------+
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// | bottom_of_stack_ | |
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// +------------------------------->| awaitable_frame |
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// | |
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// +-----------------+
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template <typename Executor>
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class awaitable_frame_base
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{
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public:
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#if !defined(BOOST_ASIO_DISABLE_AWAITABLE_FRAME_RECYCLING)
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void* operator new(std::size_t size)
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{
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return boost::asio::detail::thread_info_base::allocate(
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boost::asio::detail::thread_info_base::awaitable_frame_tag(),
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boost::asio::detail::thread_context::top_of_thread_call_stack(),
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size);
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}
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void operator delete(void* pointer, std::size_t size)
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{
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boost::asio::detail::thread_info_base::deallocate(
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boost::asio::detail::thread_info_base::awaitable_frame_tag(),
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boost::asio::detail::thread_context::top_of_thread_call_stack(),
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pointer, size);
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}
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#endif // !defined(BOOST_ASIO_DISABLE_AWAITABLE_FRAME_RECYCLING)
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// The frame starts in a suspended state until the awaitable_thread object
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// pumps the stack.
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auto initial_suspend() noexcept
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{
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return suspend_always();
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}
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// On final suspension the frame is popped from the top of the stack.
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auto final_suspend() noexcept
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{
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struct result
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{
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awaitable_frame_base* this_;
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bool await_ready() const noexcept
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{
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return false;
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}
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void await_suspend(coroutine_handle<void>) noexcept
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{
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this->this_->pop_frame();
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}
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void await_resume() const noexcept
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{
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}
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};
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return result{this};
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}
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void set_except(std::exception_ptr e) noexcept
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{
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pending_exception_ = e;
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}
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void set_error(const boost::system::error_code& ec)
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{
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this->set_except(std::make_exception_ptr(boost::system::system_error(ec)));
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}
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void unhandled_exception()
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{
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set_except(std::current_exception());
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}
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void rethrow_exception()
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{
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if (pending_exception_)
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{
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std::exception_ptr ex = std::exchange(pending_exception_, nullptr);
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std::rethrow_exception(ex);
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}
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}
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void clear_cancellation_slot()
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{
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this->attached_thread_->entry_point()->cancellation_state_.slot().clear();
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}
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template <typename T>
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auto await_transform(awaitable<T, Executor> a) const
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{
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if (attached_thread_->entry_point()->throw_if_cancelled_)
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if (!!attached_thread_->get_cancellation_state().cancelled())
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do_throw_error(boost::asio::error::operation_aborted, "co_await");
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return a;
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}
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// This await transformation obtains the associated executor of the thread of
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// execution.
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auto await_transform(this_coro::executor_t) noexcept
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{
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struct result
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{
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awaitable_frame_base* this_;
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bool await_ready() const noexcept
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{
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return true;
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}
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void await_suspend(coroutine_handle<void>) noexcept
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{
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}
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auto await_resume() const noexcept
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{
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return this_->attached_thread_->get_executor();
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}
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};
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return result{this};
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}
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// This await transformation obtains the associated cancellation state of the
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// thread of execution.
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auto await_transform(this_coro::cancellation_state_t) noexcept
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{
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struct result
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{
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awaitable_frame_base* this_;
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bool await_ready() const noexcept
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{
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return true;
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}
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void await_suspend(coroutine_handle<void>) noexcept
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{
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}
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auto await_resume() const noexcept
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{
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return this_->attached_thread_->get_cancellation_state();
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}
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};
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return result{this};
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}
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// This await transformation resets the associated cancellation state.
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auto await_transform(this_coro::reset_cancellation_state_0_t) noexcept
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{
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struct result
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{
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awaitable_frame_base* this_;
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bool await_ready() const noexcept
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{
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return true;
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}
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void await_suspend(coroutine_handle<void>) noexcept
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{
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}
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auto await_resume() const
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{
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return this_->attached_thread_->reset_cancellation_state();
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}
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};
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return result{this};
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}
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// This await transformation resets the associated cancellation state.
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template <typename Filter>
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auto await_transform(
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this_coro::reset_cancellation_state_1_t<Filter> reset) noexcept
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{
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struct result
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{
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awaitable_frame_base* this_;
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Filter filter_;
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bool await_ready() const noexcept
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{
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return true;
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}
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void await_suspend(coroutine_handle<void>) noexcept
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{
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}
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auto await_resume()
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{
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return this_->attached_thread_->reset_cancellation_state(
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BOOST_ASIO_MOVE_CAST(Filter)(filter_));
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}
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};
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return result{this, BOOST_ASIO_MOVE_CAST(Filter)(reset.filter)};
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}
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// This await transformation resets the associated cancellation state.
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template <typename InFilter, typename OutFilter>
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auto await_transform(
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this_coro::reset_cancellation_state_2_t<InFilter, OutFilter> reset)
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noexcept
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{
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struct result
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{
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awaitable_frame_base* this_;
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InFilter in_filter_;
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OutFilter out_filter_;
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bool await_ready() const noexcept
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{
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return true;
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}
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void await_suspend(coroutine_handle<void>) noexcept
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{
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}
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auto await_resume()
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{
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return this_->attached_thread_->reset_cancellation_state(
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BOOST_ASIO_MOVE_CAST(InFilter)(in_filter_),
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BOOST_ASIO_MOVE_CAST(OutFilter)(out_filter_));
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}
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};
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return result{this,
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BOOST_ASIO_MOVE_CAST(InFilter)(reset.in_filter),
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BOOST_ASIO_MOVE_CAST(OutFilter)(reset.out_filter)};
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}
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// This await transformation determines whether cancellation is propagated as
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// an exception.
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auto await_transform(this_coro::throw_if_cancelled_0_t)
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noexcept
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{
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struct result
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{
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awaitable_frame_base* this_;
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bool await_ready() const noexcept
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{
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return true;
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}
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void await_suspend(coroutine_handle<void>) noexcept
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{
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}
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auto await_resume()
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{
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return this_->attached_thread_->throw_if_cancelled();
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}
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};
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return result{this};
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}
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// This await transformation sets whether cancellation is propagated as an
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// exception.
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auto await_transform(this_coro::throw_if_cancelled_1_t throw_if_cancelled)
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noexcept
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{
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struct result
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{
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awaitable_frame_base* this_;
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bool value_;
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bool await_ready() const noexcept
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{
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return true;
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}
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void await_suspend(coroutine_handle<void>) noexcept
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{
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}
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auto await_resume()
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{
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this_->attached_thread_->throw_if_cancelled(value_);
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}
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};
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return result{this, throw_if_cancelled.value};
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}
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// This await transformation is used to run an async operation's initiation
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// function object after the coroutine has been suspended. This ensures that
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// immediate resumption of the coroutine in another thread does not cause a
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// race condition.
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template <typename Function>
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auto await_transform(Function f,
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typename enable_if<
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is_convertible<
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typename result_of<Function(awaitable_frame_base*)>::type,
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awaitable_thread<Executor>*
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>::value
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>::type* = nullptr)
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{
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struct result
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{
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Function function_;
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awaitable_frame_base* this_;
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bool await_ready() const noexcept
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{
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return false;
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}
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void await_suspend(coroutine_handle<void>) noexcept
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{
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function_(this_);
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}
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void await_resume() const noexcept
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{
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}
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};
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return result{std::move(f), this};
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}
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// Access the awaitable thread's has_context_switched_ flag.
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auto await_transform(detail::awaitable_thread_has_context_switched) noexcept
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{
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struct result
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{
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awaitable_frame_base* this_;
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bool await_ready() const noexcept
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{
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return true;
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}
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void await_suspend(coroutine_handle<void>) noexcept
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{
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}
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bool& await_resume() const noexcept
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{
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return this_->attached_thread_->entry_point()->has_context_switched_;
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}
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};
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return result{this};
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}
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void attach_thread(awaitable_thread<Executor>* handler) noexcept
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{
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attached_thread_ = handler;
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}
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awaitable_thread<Executor>* detach_thread() noexcept
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{
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attached_thread_->entry_point()->has_context_switched_ = true;
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return std::exchange(attached_thread_, nullptr);
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}
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void push_frame(awaitable_frame_base<Executor>* caller) noexcept
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{
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caller_ = caller;
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attached_thread_ = caller_->attached_thread_;
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attached_thread_->entry_point()->top_of_stack_ = this;
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caller_->attached_thread_ = nullptr;
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}
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void pop_frame() noexcept
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{
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if (caller_)
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caller_->attached_thread_ = attached_thread_;
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attached_thread_->entry_point()->top_of_stack_ = caller_;
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attached_thread_ = nullptr;
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caller_ = nullptr;
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}
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void resume()
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{
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coro_.resume();
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}
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void destroy()
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{
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coro_.destroy();
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}
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protected:
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coroutine_handle<void> coro_ = nullptr;
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awaitable_thread<Executor>* attached_thread_ = nullptr;
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awaitable_frame_base<Executor>* caller_ = nullptr;
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std::exception_ptr pending_exception_ = nullptr;
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};
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template <typename T, typename Executor>
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class awaitable_frame
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: public awaitable_frame_base<Executor>
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{
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public:
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awaitable_frame() noexcept
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{
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}
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awaitable_frame(awaitable_frame&& other) noexcept
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: awaitable_frame_base<Executor>(std::move(other))
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{
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}
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~awaitable_frame()
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{
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if (has_result_)
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static_cast<T*>(static_cast<void*>(result_))->~T();
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}
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awaitable<T, Executor> get_return_object() noexcept
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{
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this->coro_ = coroutine_handle<awaitable_frame>::from_promise(*this);
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return awaitable<T, Executor>(this);
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};
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template <typename U>
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void return_value(U&& u)
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{
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new (&result_) T(std::forward<U>(u));
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has_result_ = true;
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}
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template <typename... Us>
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void return_values(Us&&... us)
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{
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this->return_value(std::forward_as_tuple(std::forward<Us>(us)...));
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}
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T get()
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{
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this->caller_ = nullptr;
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this->rethrow_exception();
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return std::move(*static_cast<T*>(static_cast<void*>(result_)));
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}
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private:
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alignas(T) unsigned char result_[sizeof(T)];
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bool has_result_ = false;
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};
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template <typename Executor>
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class awaitable_frame<void, Executor>
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: public awaitable_frame_base<Executor>
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{
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public:
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awaitable<void, Executor> get_return_object()
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{
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this->coro_ = coroutine_handle<awaitable_frame>::from_promise(*this);
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return awaitable<void, Executor>(this);
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};
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void return_void()
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{
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}
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void get()
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{
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this->caller_ = nullptr;
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this->rethrow_exception();
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}
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};
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struct awaitable_thread_entry_point {};
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template <typename Executor>
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class awaitable_frame<awaitable_thread_entry_point, Executor>
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: public awaitable_frame_base<Executor>
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{
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public:
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awaitable_frame()
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: top_of_stack_(0),
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has_executor_(false),
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has_context_switched_(false),
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throw_if_cancelled_(true)
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{
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}
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~awaitable_frame()
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{
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if (has_executor_)
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u_.executor_.~Executor();
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}
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awaitable<awaitable_thread_entry_point, Executor> get_return_object()
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{
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this->coro_ = coroutine_handle<awaitable_frame>::from_promise(*this);
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return awaitable<awaitable_thread_entry_point, Executor>(this);
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};
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void return_void()
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{
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}
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void get()
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{
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this->caller_ = nullptr;
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this->rethrow_exception();
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}
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private:
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template <typename> friend class awaitable_frame_base;
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template <typename, typename> friend class awaitable_handler_base;
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template <typename> friend class awaitable_thread;
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union u
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{
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u() {}
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~u() {}
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char c_;
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Executor executor_;
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} u_;
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awaitable_frame_base<Executor>* top_of_stack_;
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boost::asio::cancellation_slot parent_cancellation_slot_;
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boost::asio::cancellation_state cancellation_state_;
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bool has_executor_;
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bool has_context_switched_;
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bool throw_if_cancelled_;
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};
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template <typename Executor>
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class awaitable_thread
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{
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public:
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typedef Executor executor_type;
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typedef cancellation_slot cancellation_slot_type;
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// Construct from the entry point of a new thread of execution.
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awaitable_thread(awaitable<awaitable_thread_entry_point, Executor> p,
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const Executor& ex, cancellation_slot parent_cancel_slot,
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cancellation_state cancel_state)
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: bottom_of_stack_(std::move(p))
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{
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bottom_of_stack_.frame_->top_of_stack_ = bottom_of_stack_.frame_;
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new (&bottom_of_stack_.frame_->u_.executor_) Executor(ex);
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bottom_of_stack_.frame_->has_executor_ = true;
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bottom_of_stack_.frame_->parent_cancellation_slot_ = parent_cancel_slot;
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bottom_of_stack_.frame_->cancellation_state_ = cancel_state;
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}
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// Transfer ownership from another awaitable_thread.
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awaitable_thread(awaitable_thread&& other) noexcept
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: bottom_of_stack_(std::move(other.bottom_of_stack_))
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{
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}
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// Clean up with a last ditch effort to ensure the thread is unwound within
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// the context of the executor.
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~awaitable_thread()
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{
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if (bottom_of_stack_.valid())
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{
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// Coroutine "stack unwinding" must be performed through the executor.
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auto* bottom_frame = bottom_of_stack_.frame_;
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(post)(bottom_frame->u_.executor_,
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[a = std::move(bottom_of_stack_)]() mutable
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{
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(void)awaitable<awaitable_thread_entry_point, Executor>(
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std::move(a));
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});
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}
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}
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awaitable_frame<awaitable_thread_entry_point, Executor>* entry_point()
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{
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return bottom_of_stack_.frame_;
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}
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executor_type get_executor() const noexcept
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{
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return bottom_of_stack_.frame_->u_.executor_;
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}
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cancellation_state get_cancellation_state() const noexcept
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{
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return bottom_of_stack_.frame_->cancellation_state_;
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}
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void reset_cancellation_state()
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{
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bottom_of_stack_.frame_->cancellation_state_ =
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cancellation_state(bottom_of_stack_.frame_->parent_cancellation_slot_);
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}
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template <typename Filter>
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void reset_cancellation_state(BOOST_ASIO_MOVE_ARG(Filter) filter)
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{
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bottom_of_stack_.frame_->cancellation_state_ =
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cancellation_state(bottom_of_stack_.frame_->parent_cancellation_slot_,
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BOOST_ASIO_MOVE_CAST(Filter)(filter));
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}
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template <typename InFilter, typename OutFilter>
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void reset_cancellation_state(BOOST_ASIO_MOVE_ARG(InFilter) in_filter,
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BOOST_ASIO_MOVE_ARG(OutFilter) out_filter)
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{
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bottom_of_stack_.frame_->cancellation_state_ =
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cancellation_state(bottom_of_stack_.frame_->parent_cancellation_slot_,
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BOOST_ASIO_MOVE_CAST(InFilter)(in_filter),
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BOOST_ASIO_MOVE_CAST(OutFilter)(out_filter));
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}
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bool throw_if_cancelled() const
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{
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return bottom_of_stack_.frame_->throw_if_cancelled_;
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}
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void throw_if_cancelled(bool value)
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{
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bottom_of_stack_.frame_->throw_if_cancelled_ = value;
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}
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cancellation_slot_type get_cancellation_slot() const noexcept
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{
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return bottom_of_stack_.frame_->cancellation_state_.slot();
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}
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// Launch a new thread of execution.
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void launch()
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{
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bottom_of_stack_.frame_->top_of_stack_->attach_thread(this);
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pump();
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}
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protected:
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template <typename> friend class awaitable_frame_base;
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// Repeatedly resume the top stack frame until the stack is empty or until it
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// has been transferred to another resumable_thread object.
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void pump()
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{
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do
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bottom_of_stack_.frame_->top_of_stack_->resume();
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while (bottom_of_stack_.frame_ && bottom_of_stack_.frame_->top_of_stack_);
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if (bottom_of_stack_.frame_)
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{
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awaitable<awaitable_thread_entry_point, Executor> a(
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std::move(bottom_of_stack_));
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a.frame_->rethrow_exception();
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}
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}
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awaitable<awaitable_thread_entry_point, Executor> bottom_of_stack_;
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};
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} // namespace detail
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} // namespace asio
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} // namespace boost
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#if !defined(GENERATING_DOCUMENTATION)
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# if defined(BOOST_ASIO_HAS_STD_COROUTINE)
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namespace std {
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template <typename T, typename Executor, typename... Args>
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struct coroutine_traits<boost::asio::awaitable<T, Executor>, Args...>
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{
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typedef boost::asio::detail::awaitable_frame<T, Executor> promise_type;
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};
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} // namespace std
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# else // defined(BOOST_ASIO_HAS_STD_COROUTINE)
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namespace std { namespace experimental {
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template <typename T, typename Executor, typename... Args>
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struct coroutine_traits<boost::asio::awaitable<T, Executor>, Args...>
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{
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typedef boost::asio::detail::awaitable_frame<T, Executor> promise_type;
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};
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}} // namespace std::experimental
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# endif // defined(BOOST_ASIO_HAS_STD_COROUTINE)
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#endif // !defined(GENERATING_DOCUMENTATION)
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#include <boost/asio/detail/pop_options.hpp>
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#endif // BOOST_ASIO_IMPL_AWAITABLE_HPP
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