The WComplSpanSize method

int WComplSpanSize(const ITWChar *s1, const ITWChar *s2,
            int nwchars1 = ITLocale::ScanToNul,
            int nwchars2 = ITLocale::ScanToNul) const

This method returns the number of wide characters in the maximum initial substring of the wide character string s1 that consists entirely of wide characters not in the wide character string s2.

The nwchars1 and nwchars2 parameters specify the length of the s1 and s2 strings. You can provide an integer to specify the number of characters in the corresponding string. Or you can use the constant ITLocale::ScanToNul (the default) to specify that the corresponding string is null-terminated.

If there is an error, this method returns -1. Call ITLocale::GetError() to retrieve a specific error message.