Codechange: introduce new type and functions for StringParameter backups

src/strings_type.h

@@ -88,4 +88,34 @@ enum SpecialStrings {
 	SPECSTR_PRESIDENT_NAME     = 0x70E7,
 };
 
+/** Data that is to be stored when backing up StringParameters. */
+struct StringParameterBackup {
+	uint64_t data; ///< The data field; valid *when* string has no value.
+	std::optional<std::string> string; ///< The string value.
+
+	/**
+	 * Assign the numeric data with the given value, while clearing the stored string.
+	 * @param data The new value of the data field.
+	 * @return This object.
+	 */
+	StringParameterBackup &operator=(uint64_t data)
+	{
+		this->string.reset();
+		this->data = data;
+		return *this;
+	}
+
+	/**
+	 * Assign a copy of the given string to the string field, while clearing the data field.
+	 * @param string The new value of the string.
+	 * @return This object.
+	 */
+	StringParameterBackup &operator=(const std::string_view string)
+	{
+		this->data = 0;
+		this->string.emplace(string);
+		return *this;
+	}
+};
+
 #endif /* STRINGS_TYPE_H */