1 files changed, 43 insertions, 0 deletions
diff --git a/um/service/include/libservice/singleton.hpp b/um/service/include/libservice/singleton.hpp
new file mode 100644
index 0000000..1c7b1a7
--- /dev/null
+++ b/um/service/include/libservice/singleton.hpp
@@ -0,0 +1,43 @@
+// Copyright (c) 2015 Egor Tensin <Egor.Tensin@gmail.com>
+// This file is part of the "Windows 7 drivers" project.
+// For details, see https://github.com/egor-tensin/windows7-drivers.
+// Distributed under the MIT License.
+
+#pragma once
+
+#include <mutex>
+
+namespace libservice
+{
+    template <typename DerivedT>
+    class Singleton
+    {
+    public:
+        static DerivedT& get()
+        {
+            std::call_once(initialized, initialize);
+            return get_unsafe();
+        }
+
+    protected:
+        Singleton() = default;
+        virtual ~Singleton() = default;
+
+    private:
+        static void initialize()
+        {
+            get_unsafe();
+        }
+
+        static DerivedT& get_unsafe()
+        {
+            static DerivedT instance;
+            return instance;
+        }
+
+        static std::once_flag initialized;
+    };
+
+    template <typename DerivedT>
+    std::once_flag Singleton<DerivedT>::initialized;
+}