The wcsxfrm function transforms a null-terminated wide character string pointed to by src according to the current locale collation order then copies the transformed string into dst. No more than n wide characters are copied into dst, including the terminating null character added. If n is set to 0 (it helps to determine an actual size needed for transformation), dst is permitted to be a NULL pointer.
Comparing two strings using wcscmp after wcsxfrm is equivalent to comparing two original strings with wcscoll.
Upon successful completion, wcsxfrm returns the length of the transformed string not including the terminating null character. If this value is n or more, the contents of dst are indeterminate.
setlocale(3), strxfrm(3), wcscmp(3), wcscoll(3)