cpp/locale/codecvt/encoding

@1@ public member function, calls the member function of the most derived class.

@2@ if the encoding represented by this codecvt facet maps each internal character to the same, constant number of external characters, returns that number. If the encoding is variable-length (e.g. UTF-8 or UTF-16), returns. If the encoding is state-dependent, returns.

Return value
The exact number of characters that correspond to one  character, if constant. if the number varies, if the encoding is state-dependent.

The non-converting specialization returns