1 files changed, 123 insertions, 0 deletions
diff --git a/include/armnn/Optional.hpp b/include/armnn/Optional.hpp
new file mode 100644
index 0000000000..6fc207f425
--- /dev/null
+++ b/include/armnn/Optional.hpp
@@ -0,0 +1,123 @@
+//
+// Copyright © 2017 Arm Ltd. All rights reserved.
+// SPDX-License-Identifier: MIT
+//
+#pragma once
+
+#include "Exceptions.hpp"
+
+namespace armnn
+{
+
+// NOTE: the members of the Optional class don't follow the ArmNN
+//       coding convention because the interface to be close to
+//       the C++-17 interface so we can easily migrate to std::optional
+//       later.
+
+template <typename T>
+class Optional final
+{
+public:
+    Optional(T&& value)
+        : m_HasValue{true}
+    {
+        new (m_Storage) T(value);
+    }
+
+    Optional(const T& value)
+        : m_HasValue{true}
+    {
+        new (m_Storage) T(value);
+    }
+
+    Optional(const Optional& other)
+        : m_HasValue{false}
+    {
+        *this = other;
+    }
+
+    Optional() noexcept
+        : m_HasValue{false}
+    {
+    }
+
+    ~Optional()
+    {
+        reset();
+    }
+
+    operator bool() const noexcept
+    {
+        return has_value();
+    }
+
+    Optional& operator=(T&& value)
+    {
+        reset();
+        new (m_Storage) T(value);
+        m_HasValue = true;
+        return *this;
+    }
+
+    Optional& operator=(const T& value)
+    {
+        reset();
+        new(m_Storage) T(value);
+        m_HasValue = true;
+        return *this;
+    }
+
+    Optional& operator=(const Optional& other)
+    {
+        reset();
+        if (other.has_value())
+        {
+            new (m_Storage) T(other.value());
+            m_HasValue = true;
+        }
+
+        return *this;
+    }
+
+    const T& value() const
+    {
+        if (!has_value())
+        {
+            throw BadOptionalAccessException("Optional has no value");
+        }
+
+        auto valuePtr = reinterpret_cast<const T*>(m_Storage);
+        return *valuePtr;
+    }
+
+    T& value()
+    {
+        if (!has_value())
+        {
+            throw BadOptionalAccessException("Optional has no value");
+        }
+
+        auto valuePtr = reinterpret_cast<T*>(m_Storage);
+        return *valuePtr;
+    }
+
+    bool has_value() const noexcept
+    {
+        return m_HasValue;
+    }
+
+    void reset()
+    {
+        if (has_value())
+        {
+            value().T::~T();
+            m_HasValue = false;
+        }
+    }
+
+private:
+    alignas(alignof(T)) unsigned char m_Storage[sizeof(T)];
+    bool m_HasValue;
+};
+
+}