Public interfaces: part 1

[stg.git] / include / stg / optional.h

diff --git a/include/stg/optional.h b/include/stg/optional.h
new file mode 100644 (file)
index 0000000..105d7e2
--- /dev/null
+++ b/include/stg/optional.h
@@ -0,0 +1,54 @@
+#pragma once
+
+namespace STG
+{
+
+template <typename T>
+class Optional
+{
+public:
+    using value_type = T;
+
+    Optional() noexcept : m_isSet(false) {}
+    explicit Optional(const T& value) noexcept : m_value(value), m_isSet(true) {}
+
+    Optional(const Optional<T>&) = default;
+    Optional<T>& operator=(const Optional<T>&) = default;
+
+    Optional(Optional<T>&&) = default;
+    Optional<T>& operator=(Optional<T>&&) = default;
+
+    Optional<T>& operator=(const T & rhs) noexcept
+    {
+        m_value = rhs;
+        m_isSet = true;
+        return *this;
+    }
+
+    const T & const_data() const noexcept { return m_value; }
+    T & data() noexcept { return m_value; }
+    const T & data() const noexcept { return m_value; }
+    bool empty() const noexcept { return !m_isSet; }
+    void reset() noexcept { m_isSet = false; }
+    void splice(const Optional<T>& rhs) noexcept
+    {
+        if (rhs.m_isSet)
+        {
+            m_value = rhs.m_value;
+            m_isSet = true;
+        }
+    }
+    const T& get(const T& defaultValue) const noexcept
+    {
+        if (m_isSet)
+            return m_value;
+        else
+            return defaultValue;
+    }
+
+private:
+    value_type m_value;
+    bool       m_isSet;
+};
+
+}