of the path, and going upwards. We must check the path's validity at each step. If the key is not in
the path, there is no delimiting key in the tree (buffer is first or last buffer in tree), and in this
case we return a special key, either MIN_KEY or MAX_KEY. */
of the path, and going upwards. We must check the path's validity at each step. If the key is not in
the path, there is no delimiting key in the tree (buffer is first or last buffer in tree), and in this
case we return a special key, either MIN_KEY or MAX_KEY. */