The MSpanSize method

This method returns the number of characters in the longest initial substring of multibyte character string s1 that consists entirely of multibyte characters in the string s2.

int MSpanSize(const char *s1, const char *s2, 
            int nbytes1 = ITLocale::ScanToNul, 
            int nbytes2 = ITLocale::ScanToNul) const

The nbytes1 and nbytes2 parameters specify the length of the s1 and s2 strings. You can provide an integer to specify the number of bytes 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.