add type_name.h

Event/EventPacker/src/component/type_name.h

+#include <string>
+#include <string_view>
+#include <array>   // std::array
+#include <utility> // std::index_sequence
+
+namespace details {
+  template <std::size_t...Is>
+  constexpr auto as_array(std::string_view str, std::index_sequence<Is...>) {
+    return std::array{str[Is]...};
+  }
+
+  template <typename T>
+  constexpr auto type_name_array() {
+#if defined(__clang__)
+    constexpr auto prefix   = std::string_view{"[T = "};
+    constexpr auto suffix   = std::string_view{"]"};
+    constexpr auto function = std::string_view{__PRETTY_FUNCTION__};
+#elif defined(__GNUC__)
+    constexpr auto prefix   = std::string_view{"with T = "};
+    constexpr auto suffix   = std::string_view{"]"};
+    constexpr auto function = std::string_view{__PRETTY_FUNCTION__};
+#elif defined(_MSC_VER)
+    constexpr auto prefix   = std::string_view{"type_name_array<"};
+    constexpr auto suffix   = std::string_view{">(void)"};
+    constexpr auto function = std::string_view{__FUNCSIG__};
+#else
+# error Unsupported compiler
+#endif
+
+    constexpr auto start = function.find(prefix) + prefix.size();
+    constexpr auto end = function.rfind(suffix);
+    static_assert(start < end);
+
+    constexpr auto name = function.substr(start, (end - start));
+    return as_array(name, std::make_index_sequence<name.size()>{});
+  }
+
+  template <typename T>
+  struct type_name_holder {
+    static inline constexpr auto value = type_name_array<T>();
+  };
+}
+
+template <typename T>
+constexpr std::string_view type_name()
+{
+  constexpr auto& value = details::type_name_holder<T>::value;
+  return std::string_view{value.data(), value.size()};
+}
+