+ /**
+ * @brief Convert from internal to external character set.
+ *
+ * Converts input string of intern_type to output string of
+ * extern_type. This is analogous to wcsrtombs. It does this by
+ * calling codecvt::do_out.
+ *
+ * The source and destination character sets are determined by the
+ * facet's locale, internal and external types.
+ *
+ * The characters in [from,from_end) are converted and written to
+ * [to,to_end). from_next and to_next are set to point to the
+ * character following the last successfully converted character,
+ * respectively. If the result needed no conversion, from_next and
+ * to_next are not affected.
+ *
+ * The @a state argument should be initialized if the input is at the
+ * beginning and carried from a previous call if continuing
+ * conversion. There are no guarantees about how @a state is used.
+ *
+ * The result returned is a member of codecvt_base::result. If
+ * all the input is converted, returns codecvt_base::ok. If no
+ * conversion is necessary, returns codecvt_base::noconv. If
+ * the input ends early or there is insufficient space in the
+ * output, returns codecvt_base::partial. Otherwise the
+ * conversion failed and codecvt_base::error is returned.
+ *
+ * @param state Persistent conversion state data.
+ * @param from Start of input.
+ * @param from_end End of input.
+ * @param from_next Returns start of unconverted data.
+ * @param to Start of output buffer.
+ * @param to_end End of output buffer.
+ * @param to_next Returns start of unused output area.
+ * @return codecvt_base::result.
+ */