iostate
void clear(iostate state = 0) {
void set(iostate flag) { _state |= flag;
void setstate(iostate flag) { _state |= flag; // ANSI
iostate rdstate() const { return _state; }
iostate exceptions() const { return _exceptions; }
void exceptions(iostate enable) {
istr->setstate((ios::iostate)errcode);
stream->setstate((ios::iostate)errcode);