Procedure for Using the C++ Control Class Encode Method

The procedure to encode a message using the C++ class interface is as follows:

  1. Instantiate an XML encode buffer object (OSXMLEncodeBuffer) to describe the buffer into which the message will be encoded. Constructors are available that allow a static message buffer to be specified. The default constructor specifies use of a dynamic encode buffer.

  2. Instantiate an ASN1T_<type> object and populate it with data to be encoded.

  3. Instantiate an ASN1C_<type> object to associate the message buffer with the data to be encoded.

  4. Invoke the ASN1C_<type> object Encode or EncodeTo method.

  5. Check the return status. The return value is a status value indicating whether encoding was successful or not. Zero indicates success. If encoding failed, the status value will be a negative number. The encode buffer method printErrorInfo can be invoked to get a textual explanation and stack trace of where the error occurred.

  6. If encoding was successful, get the start-of-message pointer and message length. The start-of-message pointer is obtained by calling the getMsgPtr method of the encode buffer object. If static encoding was specified (i.e., a message buffer address and size were specified to the XML Encode Buffer class constructor), the start-of-message pointer is the buffer start address. The message length is obtained by calling the getMsgLen method of the encode buffer object.

A program fragment that could be used to encode an employee record is as follows:

   #include employee.h            // include file generated by ASN1C

   main ()
   {
      OSOCTET msgbuf[4096];
      int     msglen, stat;

      // step 1: instantiate an instance of the XML encode
      // buffer class. This example specifies a static
      // message buffer..

      OSXMLEncodeBuffer encodeBuffer (msgbuf, sizeof(msgbuf));

      // step 2: populate msgData with data to be encoded

      ASN1T_PersonnelRecord msgData;
      msgData.name.givenName = "SMITH";
      ...

      // step 3: instantiate an instance of the ASN1C_<ProdName>
      // class to associate the encode buffer and message data..

      ASN1C_PersonnelRecord employee (encodeBuffer, msgData);

      // steps 4 and 5: encode and check return status

      if ((stat = employee.Encode ()) == 0)
      {
         printf ("encoded XML message:\n");
         printf ((const char*)msgbuf);
         printf (“\n”);

         // step 6: get start-of-message pointer and message length.
         // start-of-message pointer is start of msgbuf
         // call getMsgLen to get message length..

         msgptr = encodeBuffer.getMsgPtr (); // will return &msgbuf
         len = encodeBuffer.getMsgLen ();
      }
      else
      {
         printf ("Encoding failed\n");
         encodeBuffer.printErrorInfo ();
         exit (0);
      }

      // msgptr and len now describe fully encoded message

      ...