text: /* card marking write barrier. a card is a byte storing a mark flag,
  and the offset (in cells) of the first object in the card.
  
  the mark flag is set by the write barrier when an object in the
  card has a slot written to.
  
  the offset of the first object is set by the allocator. */
  
  namespace factor
  {
  
  /* if card_points_to_nursery is set, card_points_to_aging must also be set. */
  static const cell card_points_to_nursery = 0x80;
  static const cell card_points_to_aging = 0x40;
  static const cell card_mark_mask = (card_points_to_nursery | card_points_to_aging);
  typedef u8 card;
  
  static const cell card_bits = 8;
  static const cell card_size = (1<<card_bits);
  static const cell addr_card_mask = (card_size-1);
  
  typedef u8 card_deck;
  
  static const cell deck_bits = (card_bits + 10);
  static const cell deck_size = (1<<deck_bits);
  static const cell addr_deck_mask = (deck_size-1);
  
  inline cell addr_to_card(cell a)
  {
  	return a >> card_bits;
  }
  
  inline cell addr_to_deck(cell a)
  {
  	return a >> deck_bits;
  }
  }
  