_bit_mask
return ((_bitstr[_bit_idx(_bit)] & _bit_mask(_bit)) != 0);
_bitstr[_bit_idx(_bit)] |= _bit_mask(_bit);
_bitstr[_bit_idx(_bit)] &= ~_bit_mask(_bit);
((name)[_bit_byte(bit)] & _bit_mask(bit))
((name)[_bit_byte(bit)] |= _bit_mask(bit))
((name)[_bit_byte(bit)] &= ~_bit_mask(bit))