4.4 - Records

VR-Vantage uses Boost's serialization functionality for reading and writing files.

A class that contains data that is to be read from disk and written to disk is called a record.

Record classes are part of the makArchives library. The guidelines for classes in this library are as follows:

• All classes should be Records, and constructed of POD/Value semantics.
• All classes should be designed for efficient file storage.
• All files saved by VR-Vantage must represent a single Record that can be loaded using a single call.

Basic usage of records is as follows:

const std::string filename = "name.ext" SomeDataRecord rec;
//To read a file.
makArchives::DtXmlFileIo::read(filename, rec, "Name");
//To write a file.
makArchives::DtXmlFileIo::read(filename, rec, "Name");

For the most part there is a specific DataRecord type for each file type. However, some records deviate from this standard. All files in ./appData/drivers are DtDriverRecord files, for example, DIS.DtDisDriver stores a DtDriverRecord. The file extension (.DtDisDriver) is the name of the driver class needed to use the file data.

Here is an example record:

class DtTestRecord
{

   public:
 
      // All values in a record  *MUST* be initialized.
      DtTestRecord()
         : degrees(0)
         , minutes(0)
         , seconds(0.0)
      {
      }

      DtTestRecord(int d, int m, float s) 
         : degrees(d)
         , minutes(m)
         , seconds(s)
      {
      }

      int degrees;
      int minutes;
      float seconds;

   protected:

      friend class boost::serialization::access;

      // When the class Archive corresponds to an output archive, the
      // & operator is defined similar to <<. Likewise, when the class
      // Archive is a type of input archive the & operator is defined
      // similar to >>.
      template<class Archive>
      void serialize(Archive & ar, const unsigned int version)
      {
         ar & BOOST_SERIALIZATION_NVP(degrees);
         ar & BOOST_SERIALIZATION_NVP(minutes);
         ar & BOOST_SERIALIZATION_NVP(seconds);
      }
};

To write a test record:

std::string filePath = "testRecord.xml";
DtTestRecord data(35, 59, 24.567f);
makArchives::DtXmlFileIo::write(filePath, data, "DtTestRecord");  

To read a test record:

std::string filePath = "testRecord.xml";
DtTestRecord data;
makArchives::DtXmlFileIo::read(filePath, data, "DtTestRecord"); 

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