5.0

1 files changed, 62 insertions, 0 deletions

diff --git a/zen/optional.h b/zen/optional.h
new file mode 100644
index 00000000..1e04f52c
--- /dev/null
+++ b/zen/optional.h
@@ -0,0 +1,62 @@
+// **************************************************************************
+// * This file is part of the FreeFileSync project. It is distributed under *
+// * GNU General Public License: http://www.gnu.org/licenses/gpl.html       *
+// * Copyright (C) ZenJu (zhnmju123 AT gmx DOT de) - All Rights Reserved    *
+// **************************************************************************
+
+#ifndef OPTIONAL_H_2857428578342203589
+#define OPTIONAL_H_2857428578342203589
+
+namespace zen
+{
+/*
+Optional return value with static memory allocation!
+ -> interface like a pointer, performance like a value
+
+ Usage:
+ ------
+ Opt<MyEnum> someFunction();
+{
+   if (allIsWell)
+       return enumVal;
+   else
+       return NoValue();
+}
+
+ Opt<MyEnum> optValue = someFunction();
+ if (optValue)
+       ... use *optValue ...
+*/
+
+struct NoValue {};
+
+template <class T>
+class Opt
+{
+public:
+    Opt()             : valid(false), value()    {}
+    Opt(NoValue)      : valid(false), value()    {}
+    Opt(const T& val) : valid(true ), value(val) {}
+
+#ifdef _MSC_VER
+private:
+    struct ConversionToBool { int dummy; };
+public:
+    operator int ConversionToBool::* () const { return valid ? &ConversionToBool::dummy : nullptr; }
+#else
+    explicit operator bool() const { return valid; } //thank you C++11!!!
+#endif
+
+    const T& operator*() const { return value; }
+    /**/  T& operator*()       { return value; }
+
+    const T* operator->() const { return &value; }
+    /**/  T* operator->()       { return &value; }
+private:
+    const bool valid;
+    T value;
+};
+
+}
+
+#endif //OPTIONAL_H_2857428578342203589