/* conversions */
/****************************************************************************/
+/** \brief Converts an octal digit into an int.
+ * \param[in] c the octal char
+ * \return
+ * - 0–7 if c is a valid octal digit,
+ * - -1 on error.
+ */
+static inline int octval(int c) {
+ return !(c & ~127) && __m_strdigits[c] < 7 ? __m_strdigits[c] : -1;
+}
+
/** \brief Converts an hexadecimal digit into an int.
* \param[in] c the hexadecimal char
* \return