34     pub(crate) head: u16,  field
42         Self { head: 0, tail: 0 }  in new()
46         self.head == self.tail  in empty()
50         self.head != self.tail  in has_data()
54         seqnum_distance(self.head, self.tail)  in count()
58         if self.head == self.tail {  in compare()
61         if self.head < self.tail {  in compare()
62             if self.head <= pos && pos < self.tail {  in compare()
65         } else if self.head <= pos || pos < self.tail {  in compare()
68         if self.head.wrapping_sub(pos) <= pos.wrapping_sub(self.tail) {  in compare()
78             i: self.head,  in range()