BIND 10 #1803: update the RBTreeNodeChain class to identify the "previous" node

[BIND 10 Development]

#1803: update the RBTreeNodeChain class to identify the "previous" node
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                   Reporter:         |                 Owner:  vorner
  jinmei                             |                Status:  reviewing
                       Type:  task   |             Milestone:
                   Priority:         |  Sprint-20120515
  medium                             |            Resolution:
                  Component:  data   |             Sensitive:  0
  source                             |           Sub-Project:  DNS
                   Keywords:         |  Estimated Difficulty:  7
            Defect Severity:  N/A    |           Total Hours:  0
Feature Depending on Ticket:  in-    |
  memory NSEC                        |
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
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Changes (by muks):

 * owner:  muks => vorner


Comment:

 Hi vorner

 1. The `previousNode()` implementation looks good to me. I have pushed a
 few minor patches to the tree. The main thing to check are the comment
 changes. Some of the old rbtree comments were obsolete.

 2. RBNode's `successor()` and `predecessor()` are correct. But they should
 be given direct tests for edgecases. If they are not instantiable from
 outside, maybe they should be for the sake of being testable.

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Ticket URL: <http://bind10.isc.org/ticket/1803#comment:7>
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