BIND 10 #2850: Define and implement ZoneTableSegmentMapped

[BIND 10 Development]

#2850: Define and implement ZoneTableSegmentMapped
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            Reporter:  jinmei        |                        Owner:
                Type:  task          |  UnAssigned
            Priority:  medium        |                       Status:
           Component:  data source   |  reviewing
            Keywords:                |                    Milestone:
           Sensitive:  0             |  Sprint-20130514
         Sub-Project:  DNS           |                   Resolution:
Estimated Difficulty:  5             |                 CVSS Scoring:
         Total Hours:  0             |              Defect Severity:  N/A
                                     |  Feature Depending on Ticket:
                                     |  shared memory data source
                                     |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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Changes (by muks):

 * owner:  muks => UnAssigned
 * status:  assigned => reviewing


Comment:

 Putting this branch to review. I don't think a `ChangeLog` entry is
 necessary.

 The tests do not simulate unexpected conditions such as checksum failures
 and corruption (for example, where a named address may not exist). Do we
 want explicit tests for these by trying to corrupt a mapped file?

 BTW this is for corruption only; there are some amount of checks in the
 code itself, which throws if a read-write process does not setup the
 mapped file properly for a read-only process to use. These are tested by
 creating a read-only `ZoneTableSegmentMapped` after populating it with a
 read+write `ZoneTableSegmentMapped`.

-- 
Ticket URL: <http://bind10.isc.org/ticket/2850#comment:7>
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