Add ttg::detail::finally, taken from GSL

Signed-off-by: Joseph Schuchart <[email protected]>

ttg/ttg/util/finally.h

@@ -0,0 +1,57 @@
+#ifndef TTG_UTIL_FINALLY_H
+#define TTG_UTIL_FINALLY_H
+
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+namespace ttg::detail {
+
+    /* finally, taken from GSL: https://github.com/microsoft/GSL */
+
+    // final_action allows you to ensure something gets run at the end of a scope
+    template <class F>
+    class final_action
+    {
+    public:
+        explicit final_action(const F& ff) noexcept : f{ff} { }
+        explicit final_action(F&& ff) noexcept : f{std::move(ff)} { }
+
+        ~final_action() noexcept { if (invoke) f(); }
+
+        final_action(final_action&& other) noexcept
+            : f(std::move(other.f)), invoke(std::exchange(other.invoke, false))
+        { }
+
+        final_action(const final_action&)   = delete;
+        void operator=(const final_action&) = delete;
+        void operator=(final_action&&)      = delete;
+
+    private:
+        F f;
+        bool invoke = true;
+    };
+
+
+    // finally() - convenience function to generate a final_action
+    template <class F>
+    [[nodiscard]] auto finally(F&& f) noexcept
+    {
+        return final_action<std::decay_t<F>>{std::forward<F>(f)};
+    }
+
+} // namespace ttg::detail
+
+#endif // TTG_UTIL_FINALLY_H