3 files changed, 143 insertions, 0 deletions
diff --git a/src/crepe/util/CMakeLists.txt b/src/crepe/util/CMakeLists.txt
index 4be738a..94ed906 100644
--- a/src/crepe/util/CMakeLists.txt
+++ b/src/crepe/util/CMakeLists.txt
@@ -9,5 +9,7 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	Log.hpp
 	Proxy.h
 	Proxy.hpp
+	OptionalRef.h
+	OptionalRef.hpp
 )
 
diff --git a/src/crepe/util/OptionalRef.h b/src/crepe/util/OptionalRef.h
new file mode 100644
index 0000000..8417a25
--- /dev/null
+++ b/src/crepe/util/OptionalRef.h
@@ -0,0 +1,74 @@
+#pragma once
+
+namespace crepe {
+
+/**
+ * \brief Optional reference utility
+ *
+ * This class doesn't need to know the full definition of \c T to be used.
+ *
+ * \tparam T Value type
+ */
+template <typename T>
+class OptionalRef {
+public:
+	//! Initialize empty (nonexistant) reference
+	OptionalRef() = default;
+	//! Initialize reference with value
+	OptionalRef(T & ref);
+	/**
+	 * \brief Assign new reference
+	 *
+	 * \param ref Reference to assign
+	 *
+	 * \return Reference to this (required for operator)
+	 */
+  OptionalRef<T> & operator=(T & ref);
+	/**
+	 * \brief Check if this reference is not empty
+	 *
+	 * \returns `true` if reference is set, or `false` if it is not
+	 */
+	explicit operator bool() const noexcept;
+
+	/**
+	 * \brief Assign new reference
+	 *
+	 * \param ref Reference to assign
+	 */
+	void set(T &) noexcept;
+	/**
+	 * \brief Retrieve this reference
+	 *
+	 * \returns Internal reference if it is set
+	 *
+	 * \throws std::runtime_error if this function is called while the reference it not set
+	 */
+	T & get() const;
+	/**
+	 * \brief Make this reference empty
+	 */
+	void clear() noexcept;
+
+	//! Copy constructor
+  OptionalRef(const OptionalRef<T> &);
+	//! Move constructor
+  OptionalRef(OptionalRef<T> &&);
+	//! Copy assignment
+  OptionalRef<T> & operator=(const OptionalRef<T> &);
+	//! Move assignment
+  OptionalRef<T> & operator=(OptionalRef<T> &&);
+
+private:
+	/**
+	 * \brief Reference to the value of type \c T
+	 *
+	 * \note This raw pointer is *not* managed, and only used as a reference!
+	 */
+	T * ref = nullptr;
+};
+
+}
+
+#include "OptionalRef.hpp"
+
diff --git a/src/crepe/util/OptionalRef.hpp b/src/crepe/util/OptionalRef.hpp
new file mode 100644
index 0000000..7b201b0
--- /dev/null
+++ b/src/crepe/util/OptionalRef.hpp
@@ -0,0 +1,67 @@
+#pragma once
+
+#include <stdexcept>
+
+#include "OptionalRef.h"
+
+namespace crepe {
+
+template <typename T>
+OptionalRef<T>::OptionalRef(T & ref) {
+	this->set(ref);
+}
+
+template <typename T>
+OptionalRef<T>::OptionalRef(const OptionalRef<T> & other) {
+	this->ref = other.ref;
+}
+
+template <typename T>
+OptionalRef<T>::OptionalRef(OptionalRef<T> && other) {
+	this->ref = other.ref;
+	other.clear();
+}
+
+template <typename T>
+OptionalRef<T> & OptionalRef<T>::operator=(const OptionalRef<T> & other) {
+	this->ref = other.ref;
+	return *this;
+}
+
+template <typename T>
+OptionalRef<T> & OptionalRef<T>::operator=(OptionalRef<T> && other) {
+	this->ref = other.ref;
+	other.clear();
+	return *this;
+}
+
+template <typename T>
+T & OptionalRef<T>::get() const {
+	if (this->ref == nullptr)
+		throw std::runtime_error("OptionalRef: attempt to dereference nullptr");
+	return *this->ref;
+}
+
+template <typename T>
+void OptionalRef<T>::set(T & ref) noexcept {
+	this->ref = &ref;
+}
+
+template <typename T>
+void OptionalRef<T>::clear() noexcept {
+	this->ref = nullptr;
+}
+
+template <typename T>
+OptionalRef<T> & OptionalRef<T>::operator=(T & ref) {
+	this->set(ref);
+	return *this;
+}
+
+template <typename T>
+OptionalRef<T>::operator bool() const noexcept {
+	return this->ref != nullptr;
+}
+
+}
+