Update boost to 1.71 and add asio

boost/asio/awaitable.hpp

@@ -0,0 +1,125 @@
+//
+// awaitable.hpp
+// ~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2019 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_AWAITABLE_HPP
+#define BOOST_ASIO_AWAITABLE_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include <boost/asio/detail/config.hpp>
+
+#if defined(BOOST_ASIO_HAS_CO_AWAIT) || defined(GENERATING_DOCUMENTATION)
+
+#include <experimental/coroutine>
+#include <boost/asio/executor.hpp>
+
+#include <boost/asio/detail/push_options.hpp>
+
+namespace boost {
+namespace asio {
+namespace detail {
+
+using std::experimental::coroutine_handle;
+using std::experimental::suspend_always;
+
+template <typename> class awaitable_thread;
+template <typename, typename> class awaitable_frame;
+
+} // namespace detail
+
+/// The return type of a coroutine or asynchronous operation.
+template <typename T, typename Executor = executor>
+class awaitable
+{
+public:
+  /// The type of the awaited value.
+  typedef T value_type;
+
+  /// The executor type that will be used for the coroutine.
+  typedef Executor executor_type;
+
+  /// Default constructor.
+  constexpr awaitable() noexcept
+    : frame_(nullptr)
+  {
+  }
+
+  /// Move constructor.
+  awaitable(awaitable&& other) noexcept
+    : frame_(std::exchange(other.frame_, nullptr))
+  {
+  }
+
+  /// Destructor
+  ~awaitable()
+  {
+    if (frame_)
+      frame_->destroy();
+  }
+
+  /// Checks if the awaitable refers to a future result.
+  bool valid() const noexcept
+  {
+    return !!frame_;
+  }
+
+#if !defined(GENERATING_DOCUMENTATION)
+
+  // Support for co_await keyword.
+  bool await_ready() const noexcept
+  {
+    return false;
+  }
+
+  // Support for co_await keyword.
+  template <class U>
+  void await_suspend(
+      detail::coroutine_handle<detail::awaitable_frame<U, Executor>> h)
+  {
+    frame_->push_frame(&h.promise());
+  }
+
+  // Support for co_await keyword.
+  T await_resume()
+  {
+    return frame_->get();
+  }
+
+#endif // !defined(GENERATING_DOCUMENTATION)
+
+private:
+  template <typename> friend class detail::awaitable_thread;
+  template <typename, typename> friend class detail::awaitable_frame;
+
+  // Not copy constructible or copy assignable.
+  awaitable(const awaitable&) = delete;
+  awaitable& operator=(const awaitable&) = delete;
+
+  // Construct the awaitable from a coroutine's frame object.
+  explicit awaitable(detail::awaitable_frame<T, Executor>* a)
+    : frame_(a)
+  {
+  }
+
+  detail::awaitable_frame<T, Executor>* frame_;
+};
+
+} // namespace asio
+} // namespace boost
+
+#include <boost/asio/detail/pop_options.hpp>
+
+#include <boost/asio/impl/awaitable.hpp>
+
+#endif // defined(BOOST_ASIO_HAS_CO_AWAIT) || defined(GENERATING_DOCUMENTATION)
+
+#endif // BOOST_ASIO_AWAITABLE_HPP