BIND 10 #1602: Introduce dns::LabelSequence class

[BIND 10 Development]

#1602: Introduce dns::LabelSequence class
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                   Reporter:         |                 Owner:  UnAssigned
  jinmei                             |                Status:  reviewing
                       Type:  task   |             Milestone:
                   Priority:  major  |  Sprint-20120306
                  Component:         |            Resolution:
  libdns++                           |             Sensitive:  0
                   Keywords:         |           Sub-Project:  DNS
            Defect Severity:  N/A    |  Estimated Difficulty:  7
Feature Depending on Ticket:  auth   |           Total Hours:  0
  performance                        |
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
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Comment (by jinmei):

 I'm willing to review this branch but don't have time for it today,
 so if someone else is willing to, please do.

 I'd like to make some design level comments for now:

 My original intent was to keep this class as lightweight (and low
 level) as possible, and would basically refer to bare data (character
 sequence as (unsigned) char* and offset sequence as unsigned char*.
 That way coping a sequence is very cheap, and we can also consider
 creating a label sequence not from a name, such as seriazed data of a
 domain name (I expect that the memory-efficent/sharable in-memory data
 source would use something like that).

 Of course handling such low-level data is dangerous.  Overall it's a
 tradeoff between safety and efficency (and this class will be expected
 to be used by a limited class of performance sensitive applications).

 So, if it's not very difficult, I'd suggest considering the use of
 such low level internal representation.

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Ticket URL: <http://bind10.isc.org/ticket/1602#comment:8>
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