Defined in header <cstdlib> int mblen( const char* s, std::size_t n );
Determines the size, in bytes, of the multibyte character whose first byte is pointed to by s.
If s is a null pointer, resets the global conversion state and determined whether shift sequences are used.
This function is equivalent to the call std::mbtowc((wchar_t*)0, s, n), except that conversion state of std::mbtowc is unaffected.
Notes
Each call to mblen updates the internal global conversion state