cpp-common/vendor: add copy of wise_enum

[babeltrace.git] / src / cpp-common / vendor / wise-enum / optional.h

diff --git a/src/cpp-common/vendor/wise-enum/optional.h b/src/cpp-common/vendor/wise-enum/optional.h
new file mode 100644 (file)
index 0000000..6b0dab1
--- /dev/null
+++ b/src/cpp-common/vendor/wise-enum/optional.h
@@ -0,0 +1,82 @@
+#pragma once
+
+#include "optional_common.h"
+
+#include <stdexcept>
+#include <type_traits>
+
+#if __cplusplus == 201103
+#define WISE_ENUM_CONSTEXPR_14
+#else
+#define WISE_ENUM_CONSTEXPR_14 constexpr
+#endif
+
+namespace wise_enum {
+
+/* A simple, *forward* compatible optional implementation. That is, it does not
+ * provide the full std::optional interface, but all the interface it does
+ * provide is found on std::optional, so it should not be a breaking change to
+ * upgrade to std::optional.
+ */
+template <class T>
+class optional {
+public:
+  static_assert(std::is_enum<T>::value,
+                "wise enum optional is only for enum types");
+  optional() = default;
+  optional(T t) : m_t(t), m_active(true) {}
+
+  WISE_ENUM_CONSTEXPR_14 T &operator*() & { return m_t; }
+  constexpr const T &operator*() const & { return m_t; }
+  WISE_ENUM_CONSTEXPR_14 T &&operator*() && { return m_t; }
+  constexpr const T &&operator*() const && { return m_t; }
+
+  constexpr explicit operator bool() const noexcept { return m_active; }
+  constexpr bool has_value() const noexcept { return m_active; }
+
+  WISE_ENUM_CONSTEXPR_14 T &value() & {
+    if (m_active)
+      return m_t;
+    else
+      WISE_ENUM_OPTIONAL_BAD_ACCESS;
+  }
+  WISE_ENUM_CONSTEXPR_14 const T &value() const & {
+    if (m_active)
+      return m_t;
+    else
+      WISE_ENUM_OPTIONAL_BAD_ACCESS;
+  }
+
+  WISE_ENUM_CONSTEXPR_14 T &&value() && {
+    if (m_active)
+      return m_t;
+    else
+      WISE_ENUM_OPTIONAL_BAD_ACCESS;
+  }
+  WISE_ENUM_CONSTEXPR_14 const T &&value() const && {
+    if (m_active)
+      return m_t;
+    else
+      WISE_ENUM_OPTIONAL_BAD_ACCESS;
+  }
+
+  template <class U>
+  WISE_ENUM_CONSTEXPR_14 T value_or(U &&u) {
+    if (m_active)
+      return m_t;
+    else
+      return std::forward<U>(u);
+  }
+
+  void reset() noexcept { m_active = false; }
+
+  optional(const optional &other) = default;
+  optional(optional &&other) = default;
+  optional &operator=(const optional &other) = default;
+  optional &operator=(optional &&other) = default;
+
+private:
+  T m_t;
+  bool m_active = false;
+};
+} // namespace wise_enum