lib/base: Implement pattern to execute something at function exit

src/lib/base/finally.h

@@ -0,0 +1,61 @@
+/*
+    barrier -- mouse and keyboard sharing utility
+    Copyright (C) Barrier contributors
+
+    This package is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License
+    found in the file LICENSE that should have accompanied this file.
+
+    This package 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 General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef BARRIER_LIB_BASE_FINALLY_H
+#define BARRIER_LIB_BASE_FINALLY_H
+
+#include <utility>
+
+namespace barrier {
+
+// this implements a common pattern of executing an action at the end of function
+
+template<class Callable>
+class final_action {
+public:
+    final_action() noexcept {}
+    final_action(Callable callable) noexcept : callable_{callable} {}
+
+    ~final_action() noexcept
+    {
+        if (!invoked_) {
+            callable_();
+        }
+    }
+
+    final_action(final_action&& other) noexcept :
+        callable_{std::move(other.callable_)}
+    {
+        std::swap(invoked_, other.invoked_);
+    }
+
+    final_action(const final_action&) = delete;
+    final_action& operator=(const final_action&) = delete;
+private:
+    bool invoked_ = false;
+    Callable callable_;
+};
+
+template<class Callable>
+inline final_action<Callable> finally(Callable&& callable) noexcept
+{
+    return final_action<Callable>(std::forward<Callable>(callable));
+}
+
+} // namespace barrier
+
+#endif // BARRIER_LIB_BASE_FINALLY_H