From 1cb3db6726a1bb3dcb639d7c0ec6eb93433f3ff8 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Wed, 2 Jan 2019 15:18:15 -0800
Subject: [PATCH] ircd::util: Add scope_restore; remove scope_light because
 generalized.

---
 include/ircd/util/scope_light.h   | 48 -----------------------
 include/ircd/util/scope_restore.h | 65 +++++++++++++++++++++++++++++++
 include/ircd/util/util.h          |  2 +-
 3 files changed, 66 insertions(+), 49 deletions(-)
 delete mode 100644 include/ircd/util/scope_light.h
 create mode 100644 include/ircd/util/scope_restore.h

diff --git a/include/ircd/util/scope_light.h b/include/ircd/util/scope_light.h
deleted file mode 100644
index 4a1b0923f..000000000
--- a/include/ircd/util/scope_light.h
+++ /dev/null
@@ -1,48 +0,0 @@
-// Matrix Construct
-//
-// Copyright (C) Matrix Construct Developers, Authors & Contributors
-// Copyright (C) 2016-2019 Jason Volk <jason@zemos.net>
-//
-// Permission to use, copy, modify, and/or distribute this software for any
-// purpose with or without fee is hereby granted, provided that the above
-// copyright notice and this permission notice is present in all copies. The
-// full license for this software is available in the LICENSE file.
-
-#pragma once
-#define HAVE_IRCD_UTIL_SCOPE_LIGHT_H
-
-namespace ircd::util
-{
-	struct scope_light;
-};
-
-/// A simple boiler-plate  for setting a bool to true when constructed and
-/// resetting it to its previous value when destructed. This takes a runtime
-/// reference to that bool. This is not intended to be a replacement for the
-/// reentrance_assertion utility or ctx::mutex et al.
-struct ircd::util::scope_light
-{
-	bool *light {nullptr};
-	bool theirs {false};
-
-	scope_light(bool &light);
-	scope_light(const scope_light &) = delete;
-	scope_light(scope_light &&) noexcept = delete;
-	~scope_light() noexcept;
-};
-
-inline
-ircd::util::scope_light::scope_light(bool &light)
-:light{&light}
-,theirs{light}
-{
-	light = true;
-}
-
-inline
-ircd::util::scope_light::~scope_light()
-noexcept
-{
-	assert(light);
-	*light = theirs;
-}
diff --git a/include/ircd/util/scope_restore.h b/include/ircd/util/scope_restore.h
new file mode 100644
index 000000000..1179458e0
--- /dev/null
+++ b/include/ircd/util/scope_restore.h
@@ -0,0 +1,65 @@
+// Matrix Construct
+//
+// Copyright (C) Matrix Construct Developers, Authors & Contributors
+// Copyright (C) 2016-2019 Jason Volk <jason@zemos.net>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice is present in all copies. The
+// full license for this software is available in the LICENSE file.
+
+#pragma once
+#define HAVE_IRCD_UTIL_SCOPE_RESTORE_H
+
+namespace ircd::util
+{
+	template<class T> struct scope_restore;
+};
+
+template<class T>
+struct ircd::util::scope_restore
+{
+	T *restore {nullptr};
+	T theirs;
+
+	scope_restore(T &restore);
+	scope_restore(T &restore, T&& ours);
+	template<class... args> scope_restore(T &restore, args&&... ours);
+	scope_restore(const scope_restore &) = delete;
+	scope_restore(scope_restore &&) noexcept = delete;
+	~scope_restore() noexcept;
+};
+
+template<class T>
+ircd::util::scope_restore<T>::scope_restore(T &restore)
+:restore{&restore}
+,theirs{std::move(restore)}
+{
+}
+
+template<class T>
+ircd::util::scope_restore<T>::scope_restore(T &restore,
+                                            T&& ours)
+:restore{&restore}
+,theirs{std::move(restore)}
+{
+	restore = std::forward<T>(ours);
+}
+
+template<class T>
+template<class... args>
+ircd::util::scope_restore<T>::scope_restore(T &restore,
+                                            args&&... ours)
+:restore{&restore}
+,theirs{std::move(restore)}
+{
+	new (&restore) T(std::forward<args>(ours)...);
+}
+
+template<class T>
+ircd::util::scope_restore<T>::~scope_restore()
+noexcept
+{
+	assert(restore);
+	*restore = std::move(theirs);
+}
diff --git a/include/ircd/util/util.h b/include/ircd/util/util.h
index 4f7097711..0bbde7a48 100644
--- a/include/ircd/util/util.h
+++ b/include/ircd/util/util.h
@@ -45,8 +45,8 @@ namespace ircd
 #include "bswap.h"
 #include "tuple.h"
 #include "timer.h"
-#include "scope_light.h"
 #include "scope_count.h"
+#include "scope_restore.h"
 #include "life_guard.h"
 #include "pubsetbuf.h"
 #include "string.h"