Initial Commit

include/asio/detail/completion_payload.hpp

@@ -0,0 +1,220 @@
+//
+// detail/completion_payload.hpp
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+//
+// Copyright (c) 2003-2025 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_COMPLETION_PAYLOAD_HPP
+#define ASIO_DETAIL_COMPLETION_PAYLOAD_HPP
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1200)
+# pragma once
+#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
+
+#include "asio/detail/config.hpp"
+#include "asio/detail/type_traits.hpp"
+#include "asio/error_code.hpp"
+#include "asio/detail/completion_message.hpp"
+
+#if defined(ASIO_HAS_STD_VARIANT)
+# include <variant>
+#else // defined(ASIO_HAS_STD_VARIANT)
+# include <new>
+#endif // defined(ASIO_HAS_STD_VARIANT)
+
+#include "asio/detail/push_options.hpp"
+
+namespace asio {
+namespace detail {
+
+template <typename... Signatures>
+class completion_payload;
+
+template <typename R>
+class completion_payload<R()>
+{
+public:
+  explicit completion_payload(completion_message<R()>)
+  {
+  }
+
+  template <typename Handler>
+  void receive(Handler& handler)
+  {
+    static_cast<Handler&&>(handler)();
+  }
+};
+
+template <typename Signature>
+class completion_payload<Signature>
+{
+public:
+  completion_payload(completion_message<Signature>&& m)
+    : message_(static_cast<completion_message<Signature>&&>(m))
+  {
+  }
+
+  template <typename Handler>
+  void receive(Handler& handler)
+  {
+    message_.receive(handler);
+  }
+
+private:
+  completion_message<Signature> message_;
+};
+
+#if defined(ASIO_HAS_STD_VARIANT)
+
+template <typename... Signatures>
+class completion_payload
+{
+public:
+  template <typename Signature>
+  completion_payload(completion_message<Signature>&& m)
+    : message_(static_cast<completion_message<Signature>&&>(m))
+  {
+  }
+
+  template <typename Handler>
+  void receive(Handler& handler)
+  {
+    std::visit(
+        [&](auto& message)
+        {
+          message.receive(handler);
+        }, message_);
+  }
+
+private:
+  std::variant<completion_message<Signatures>...> message_;
+};
+
+#else // defined(ASIO_HAS_STD_VARIANT)
+
+template <typename R1, typename R2>
+class completion_payload<R1(), R2(asio::error_code)>
+{
+public:
+  typedef completion_message<R1()> void_message_type;
+  typedef completion_message<R2(asio::error_code)> error_message_type;
+
+  completion_payload(void_message_type&&)
+    : message_(0, asio::error_code()),
+      empty_(true)
+  {
+  }
+
+  completion_payload(error_message_type&& m)
+    : message_(static_cast<error_message_type&&>(m)),
+      empty_(false)
+  {
+  }
+
+  template <typename Handler>
+  void receive(Handler& handler)
+  {
+    if (empty_)
+      completion_message<R1()>(0).receive(handler);
+    else
+      message_.receive(handler);
+  }
+
+private:
+  error_message_type message_;
+  bool empty_;
+};
+
+template <typename Sig1, typename Sig2>
+class completion_payload<Sig1, Sig2>
+{
+public:
+  typedef completion_message<Sig1> message_1_type;
+  typedef completion_message<Sig2> message_2_type;
+
+  completion_payload(message_1_type&& m)
+    : index_(1)
+  {
+    new (&storage_.message_1_) message_1_type(static_cast<message_1_type&&>(m));
+  }
+
+  completion_payload(message_2_type&& m)
+    : index_(2)
+  {
+    new (&storage_.message_2_) message_2_type(static_cast<message_2_type&&>(m));
+  }
+
+  completion_payload(completion_payload&& other)
+    : index_(other.index_)
+  {
+    switch (index_)
+    {
+    case 1:
+      new (&storage_.message_1_) message_1_type(
+          static_cast<message_1_type&&>(other.storage_.message_1_));
+      break;
+    case 2:
+      new (&storage_.message_2_) message_2_type(
+          static_cast<message_2_type&&>(other.storage_.message_2_));
+      break;
+    default:
+      break;
+    }
+  }
+
+  ~completion_payload()
+  {
+    switch (index_)
+    {
+    case 1:
+      storage_.message_1_.~message_1_type();
+      break;
+    case 2:
+      storage_.message_2_.~message_2_type();
+      break;
+    default:
+      break;
+    }
+  }
+
+  template <typename Handler>
+  void receive(Handler& handler)
+  {
+    switch (index_)
+    {
+    case 1:
+      storage_.message_1_.receive(handler);
+      break;
+    case 2:
+      storage_.message_2_.receive(handler);
+      break;
+    default:
+      break;
+    }
+  }
+
+private:
+  union storage
+  {
+    storage() {}
+    ~storage() {}
+
+    char dummy_;
+    message_1_type message_1_;
+    message_2_type message_2_;
+  } storage_;
+  unsigned char index_;
+};
+
+#endif // defined(ASIO_HAS_STD_VARIANT)
+
+} // namespace detail
+} // namespace asio
+
+#include "asio/detail/pop_options.hpp"
+
+#endif // ASIO_DETAIL_COMPLETION_PAYLOAD_HPP