Z_MASK
(h->flags & Z_MASK),
if ((h.flags & Z_MASK) != 0)
((h->flags & Z_MASK) >> Z_SHIFT),
((h->flags & Z_MASK) >> Z_SHIFT),
#define Z(packet) (*buffer_at((packet), 3) & Z_MASK)
#define Z_SET(packet) (*buffer_at((packet), 3) |= Z_MASK)
#define Z_CLR(packet) (*buffer_at((packet), 3) &= ~Z_MASK)