BIND 10 #2850: Define and implement ZoneTableSegmentMapped

[BIND 10 Development]

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

Comment (by jinmei):

 While reviewing #2836 I noticed one related thing: memory remapping
 can happen in `ZoneWriter::load()` and `ZoneWriter::install()`,
 which could invalidate the zone table header address (return value
 of getHeader()).

 So, we'll need something like this:

 - add another virtual method to `ZoneTableSegment`:
 {{{#!cpp
     // update header_ by getting the address of ZONE_TABLE_HEADER_NAME
 again.
     // (local version can be nop.)
     virtual void resetHeader() = 0;
 }}}
 - and update load() and install() as follows:
 {{{#!cpp
 void
 ZoneWriter::load() {
     if (state_ != ZW_UNUSED) {
         isc_throw(isc::InvalidOperation, "Trying to load twice");
     }

     zone_data_ = load_action_(segment_.getMemorySegment());

     if (!zone_data_) {
         // Bug inside load_action_.
         isc_throw(isc::InvalidOperation, "No data returned from load
 action");
     }

     segment_.resetHeader();

     state_ = ZW_LOADED;
 }

 void
 ZoneWriter::install() {
     if (state_ != ZW_LOADED) {
         isc_throw(isc::InvalidOperation, "No data to install");
     }

     ZoneTable* table(segment_.getHeader().getTable());
     if (!table) {
         isc_throw(isc::Unexpected, "No zone table present");
     }
     const ZoneTable::AddResult result(table->addZone(
                                           segment_.getMemorySegment(),
                                           rrclass_, origin_, zone_data_));

     state_ = ZW_INSTALLED;
     zone_data_ = result.zone_data;
     segment_.resetHeader();
 }
 }}}

 If you think these are too much for this task, I'm okay with deferring
 it to a separate ticket.

-- 
Ticket URL: <http://bind10.isc.org/ticket/2850#comment:19>
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