public static unsafe bool Equals (string a, string b)
                {
                        if ((a as object) == (b as object))
                                return true;

                        if (a == null || b == null)
                                return false;

                        int len = a.length;

                        if (len != b.length)
                                return false;

                        if (len == 0)
                                return true;

                        fixed (char * s1 = &a.start_char, s2 = &b.start_char) {
                                // it must be one char, because 0 len is done above
                                if (len < 2)
                                        return *s1 == *s2;

                                // check by twos
                                int * sint1 = (int *) s1, sint2 = (int *) s2;
                                int n2 = len >> 1;
                                do {
                                        if (*sint1++ != *sint2++)
                                                return false;
                                } while (--n2 != 0);

                                // nothing left
                                if ((len & 1) == 0)
                                        return true;

                                // check the last one
                                return *(char *) sint1 == *(char *) sint2;
                        }
                }