refs #628 Refactor CWorker::invoke into a free function and expand its API.

src/blackmisc/invoke.h

@@ -0,0 +1,56 @@
+/* Copyright (C) 2015
+ * swift Project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ */
+
+//! \file
+
+#ifndef BLACKMISC_INVOKE_H
+#define BLACKMISC_INVOKE_H
+
+#include <type_traits>
+
+namespace BlackMisc
+{
+    //! \cond PRIVATE
+    namespace Private
+    {
+
+        // Our own version of C++17 std::invoke().
+        template <typename F, typename T, typename = std::enable_if_t<std::is_member_object_pointer<F>::value>>
+        decltype(auto) invoke(F ptr, T &&object)
+        {
+            return std::forward<T>(object).*ptr;
+        }
+        template <typename F, typename T, typename... Ts, typename = std::enable_if_t<std::is_member_function_pointer<F>::value>>
+        decltype(auto) invoke(F ptr, T &&object, Ts &&... args)
+        {
+            return (std::forward<T>(object).*ptr)(std::forward<Ts>(args)...);
+        }
+        template <typename F, typename... Ts, typename = std::enable_if_t<! std::is_member_pointer<std::decay_t<F>>::value>>
+        decltype(auto) invoke(F &&func, Ts &&... args)
+        {
+            return std::forward<F>(func)(std::forward<Ts>(args)...);
+        }
+
+        // Like invoke() but ignores the first argument if callable is not a member function. For uniform calling of callables with slot semantics.
+        template <typename F, typename T, typename... Ts, typename = std::enable_if_t<std::is_member_function_pointer<F>::value>>
+        decltype(auto) invokeSlot(F ptr, T *object, Ts &&... args)
+        {
+            return (object->*ptr)(std::forward<Ts>(args)...);
+        }
+        template <typename F, typename T, typename... Ts, typename = std::enable_if_t<! std::is_member_pointer<std::decay_t<F>>::value>>
+        decltype(auto) invokeSlot(F &&func, T *, Ts &&... args)
+        {
+            return std::forward<F>(func)(std::forward<Ts>(args)...);
+        }
+
+    }
+    //! \endcond
+}
+
+#endif