+ /** returns a pointer to the buffer that follows argument in
+ * buffer list. The buffer following the last in list is the
+ * first one.
+ */
+ Buffer * next(Buffer const *) const;
+
+ /** returns a pointer to the buffer that precedes argument in
+ * buffer list. The buffer preceding the first in list is the
+ * last one.
+ */
+ Buffer * previous(Buffer const *) const;
+