function is the wide-character equivalent
It returns the number of wide-characters in the string pointed to by
s, not including the terminating L'\0' character, but at most
In doing this,
looks only at the first maxlen
wide-characters at s and never beyond s+maxlen.
function returns wcslen(s), if that is less than
maxlen, or maxlen if there is no L'\0' character among the
first maxlen wide characters pointed to by s.
function is provided in glibc since version 2.1.