[mapguide-trac] #1538: Speed up Coordinate System Dictionary lookup when reading all CS definitions at one

[MapGuide Open Source]

#1538: Speed up Coordinate System Dictionary lookup when reading all CS
definitions at one
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   Reporter:  baertelchen  |       Owner:  baertelchen          
       Type:  enhancement  |      Status:  new                  
   Priority:  low          |   Milestone:  2.3                  
  Component:  General      |     Version:  2.1.0                
   Severity:  minor        |    Keywords:  Coordinate System API
External_id:               |  
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 When reading all available coordinate system definitions from the
 dictionary (in this case, from coordsys.csd), the current implementation
 does (way too) many file look ups via CsMap. For each(!) CS definition to
 be read (out of thousands), the implementation will first read the CS'
 name (1), this name is later taken to read the CS' definition (2). When
 creating the MgCoordinateSystem instance, the CS' datum is taken and the
 MgCsDatum instance is created(3). While creating the MgCsDatum instance,
 the MgEllipsoid instance is also created (4).

 The numbers indicate the file accesses via CsMap. This includes a global
 in-process lock, the file access itself inside CsMap (which does a divide-
 and-conquer-like search within the file) and the construction of the
 object.

 This ticket is to fix the implementation of
 [MgCoordinateSystemEnum::Next(UINT32 ulCount)] in
 [CoordSysEnum::Next(UINT32 ulCount)] as returned by the
 [CoordSysDictionary] class.

 That is, when an API client is about to read ALL available systems (as
 indicated by the UINT32 ulCount parameter), the lookup has to be much
 faster.

-- 
Ticket URL: <http://trac.osgeo.org/mapguide/ticket/1538>
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