Procedure for Using the C++ Control Class Decode Method

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The following are the steps are involved in decoding an XML message using the generated C++ class:

1. Instantiate an XML decode buffer object (OSXMLDecodeBuffer) to describe the message to be decoded. There are several choices of constructors that can be used including one that takes the name of a file which contains the XML message, one the allows a memory buffer to be specified, and one that allows an existing stream object to be used.

2. Instantiate an ASN1T_<ProdName> object to hold the decoded message data.

3. Instantiate an ASN1C_<ProdName> object to decode the message. This class associates the message buffer object with the object that is to receive the decoded data. The results of the decode operation will be placed in the variable declared in step 2.

4. Invoke the ASN1C_<ProdName> object Decode or DecodeFrom method.

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

6. Release dynamic memory that was allocated by the decoder. All memory associated with the decode context is released when both the OSXMLDecodeBuffer and ASN1C_<ProdName> objects go out of scope.

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

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

 
    main ()
 
    {
 
       const char*  filename = "message.xml";
 
       OSBOOL       verbose = FALSE, trace = TRUE;
 
       int          i, stat;
 

 
       .. logic to read message into msgbuf ..
 

 
       // step 1: instantiate an XML decode buffer object
 

 
       OSXMLDecodeBuffer decodeBuffer (filename);
 

 
       // step 2: instantiate an ASN1T_<ProdName> object
 

 
       ASN1T_PersonnelRecord msgData;
 

 
       // step 3: instantiate an ASN1C_<ProdName> object
 

 
       ASN1C_PersonnelRecord employee (decodeBuffer, msgData);
 

 
       // step 4: decode the record
 

 
       stat = employee.Decode ();
 

 
       // step 5: check the return status
 

 
       if (stat == 0)
 
       {
 
           process received data..
 
       }
 
       else {
 
           // error processing..
 
           decodeBuffer.PrintErrorInfo ();
 
       }
 

 
       // step 6: free dynamic memory (will be done automatically 
 
       // when both the decodeBuffer and employee objects go out 
 
       // of scope)..
 

 
    }