+
+ /** @brief Flush callback
+ * @param s Sink to write to
+ * @return non-negative on success, -1 on error
+ */
+ int (*flush)(struct sink *s);
+
+ /** @brief Error callback
+ * @param s Sink
+ * @return Last error code
+ */
+ int (*error)(struct sink *s);
+
+ enum error_class eclass;