Merge pull request #1696 from G10h4ck/modern_cpp

Take advantage of modern C++ features

libretroshare/src/util/cxx17retrocompat.h

@@ -0,0 +1,35 @@
+/*******************************************************************************
+ * libretroshare/src/util: cxx17retrocompat.h                                  *
+ *                                                                             *
+ * libretroshare: retroshare core library                                      *
+ *                                                                             *
+ * Copyright (C) 2019  Gioacchino Mazzurco <gio@eigenlab.org>                  *
+ *                                                                             *
+ * This program is free software: you can redistribute it and/or modify        *
+ * it under the terms of the GNU Lesser General Public License as              *
+ * published by the Free Software Foundation, either version 3 of the          *
+ * License, or (at your option) any later version.                             *
+ *                                                                             *
+ * This program is distributed in the hope that it will be useful,             *
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of              *
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the                *
+ * GNU Lesser General Public License for more details.                         *
+ *                                                                             *
+ * You should have received a copy of the GNU Lesser General Public License    *
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.       *
+ *                                                                             *
+ *******************************************************************************/
+#pragma once
+
+#if __cplusplus < 201703L
+
+#include <type_traits>
+
+namespace std
+{
+using namespace std;
+template <class T> constexpr typename add_const<T>::type& as_const(T& t) noexcept
+{ return t; }
+template <class T> void as_const(const T&&) = delete;
+}
+#endif // __cplusplus < 201703L

libretroshare/src/util/rsmemory.h

@@ -62,6 +62,35 @@ bool myFunnyFunction(
  */
 #define RS_DEFAULT_STORAGE_PARAM(Type,...) *std::unique_ptr<Type>(new Type(__VA_ARGS__))
 
+
+/** @brief Safely dynamic cast between std::unique_ptr of different types
+ * std::unique_ptr semantic rely on the invariant that only one instance own
+ * the object, when casting between differents types one would be tempted to do
+ * it in a one liner that easly end up breaking that condition ending up in a
+ * double delete and crash or in a silent memleak.
+ * With this function one can do that with same comfort of a plain dynamic_cast,
+ * plus the std::unique_ptr safety.
+ * @param[inout] src reference to source pointer. If the cast is successfull it
+ *	is released, otherwise it is left untouched.
+ * @param[out] dst reference to destination pointer. If the cast is successful
+ *	it get reseated to the object address, otherwise it is left untouched.
+ * @return true on success, false otherwise
+ */
+template <class T_SRC, class T_DST>
+bool rs_unique_cast(
+        std::unique_ptr<T_SRC>& src, std::unique_ptr<T_DST>& dst )
+{
+	T_DST* dstPtr = dynamic_cast<T_DST*>(src.get());
+	if(dstPtr)
+	{
+		src.release();
+		dst.reset(dstPtr);
+		return true;
+	}
+	return false;
+}
+
+
 void *rs_malloc(size_t size) ;
 
 // This is a scope guard to release the memory block when going of of the current scope.