BIND 10 #2092: RBNode parent pointer updates

[BIND 10 Development]

#2092: RBNode parent pointer updates
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                   Reporter:         |                 Owner:
  jinmei                             |                Status:  new
                       Type:  task   |             Milestone:  Next-Sprint-
                   Priority:         |  Proposed
  medium                             |            Resolution:
                  Component:  data   |             Sensitive:  0
  source                             |           Sub-Project:  DNS
                   Keywords:         |  Estimated Difficulty:  0
            Defect Severity:  N/A    |           Total Hours:  0
Feature Depending on Ticket:         |
  scalable inmemory                  |
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
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Description changed by jinmei:

Old description:

> - Make sure the parent of a root node (of some subtree) points to the
>   upper level node (it's currently NULL; the root node should be
>   distinguishable by the newly introduced "ROOT" flag)
> - Introduce a new method "getUpLevelNode" (or rename it as
>   appropriate).  It takes a node and returns the parent of the rot
>   of its subtree (i.e, it returns the node's immediate ancestor in
>   the domain hierarchy).  If the node is at the top level (which
>   should be absolute), it will return the null node
> - at this point, we should probably consider replacing the sentinel
>   NULL node with a NULL pointer.  In my experiment I found it could
>   be quite confusing if we have both the concept of "root" and
>   "NULL node"

New description:

 - Make sure the parent of a root node (of some subtree) points to the
   upper level node (it's currently NULL; the root node should be
   distinguishable by the newly introduced "ROOT" flag)
 - Introduce a new method "getUpLevelNode" (or rename it as
   appropriate).  It takes a node and returns the parent of the root
   of its subtree (i.e, it returns the node's immediate ancestor in
   the tree-of-tree hierarchy).  If the node is at the top level (which
   should be absolute), it will return the null node
 - at this point, we should probably consider replacing the sentinel
   NULL node with a NULL pointer.  In my experiment I found it could
   be quite confusing if we have both the concept of "root" and
   "NULL node"

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Ticket URL: <http://bind10.isc.org/ticket/2092#comment:1>
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