36   SnapshotImpl* next_;  variable
50     list_.next_ = &list_;  in SnapshotList()
62   bool empty() const { return list_.next_ == &list_; }  in empty()
63   SnapshotImpl* oldest() const { assert(!empty()); return list_.next_; }  in oldest()
72     s->next_ = &list_;  in New()
74     s->prev_->next_ = s;  in New()
75     s->next_->prev_ = s;  in New()
83     s->prev_->next_ = s->next_;  in Delete()
84     s->next_->prev_ = s->prev_;  in Delete()
113     while (s->next_ != &list_) {
114       if (s->next_->number_ > max_seq) {
118       if (ret.empty() || ret.back() != s->next_->number_) {
119         ret.push_back(s->next_->number_);
124           s->next_->is_write_conflict_boundary_) {
127         *oldest_write_conflict_snapshot = s->next_->number_;
130       s = s->next_;