wcsspn function — Counts characters that match a span set
size_t wcsspn(const wchar_t* str, const wchar_t* spanset)
The wcsspn function returns the number of wide characters at the start of str that are in the string spanset.
wcsspn
str
spanset
wcschr function, wcscspn function, wcspbrk function, strspn in <cstring>
strspn
<cstring>