kern: add abstract scoped lock template

libraries/libmesosphere/include/mesosphere/kern_k_scoped_lock.hpp

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2018-2020 Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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/>.
+ */
+#pragma once
+#include <mesosphere/kern_common.hpp>
+
+namespace ams::kern {
+
+    /*
+        TODO: C++20
+
+        template<typename T>
+        concept KLockable = !std::is_reference<T>::value && requires (T &t) {
+            { t.Lock()  } -> std::same_as<void>;
+            { t.Unlock() } -> std::same_as<void>;
+        };
+
+    */
+
+    template<typename T> /* TODO C++20: requires KLockable<T> */
+    class KScopedLock {
+        NON_COPYABLE(KScopedLock);
+        NON_MOVEABLE(KScopedLock);
+        private:
+            T *lock_ptr;
+        public:
+            explicit ALWAYS_INLINE KScopedLock(T *l) : lock_ptr(l) { this->lock_ptr->Lock(); }
+            explicit ALWAYS_INLINE KScopedLock(T &l) : KScopedLock(std::addressof(l)) { /* ... */}
+            ALWAYS_INLINE ~KScopedLock() { this->lock_ptr->Unlock(); }
+    };
+
+}