public static int dehexchar (char c) {
        if (c >= '0' && c <= '9') { return c - '0'; }
        if (c >= 'A' && c <= 'F') { return c - ('A' - 10); }
        if (c >= 'a' && c <= 'f') { return c - ('a' - 10); }
        return -1;
    }