D-Bus low-lewel API - sending an array of structures

[Bogdan Lotko]

Hello,

Could somebody please analyze the piece of source code below.

I'd like to send a message containing an array of structures using 
low-level API. The sent message shall be received in Qt.
For the test purposes the structure is a two-string structure, the array 
contains 10 entries.

The receiver side (Qt) defines following parameter for the slot method 
(Q_DECLARE METATYPE are omitted here):

structure
{
   QString str1;
   QString str2;
} twoString;

typedef QVector<twoString> structArr;

void slotMethod( structArr arr );

Now to the sender. I have to use low-level API :(.
Running the example below I get the following run-time error:

-------------------PASSED_0
-------------------PASSED_1
process 6585: Array or variant type requires that type struct be 
written, but begin_struct was written
   D-Bus not built with -rdynamic so unable to print a backtrace

And now the source code:

gboolean arrayOfStructSignal( MyClass *self )
{
   // unique number
   dbus_uint32_t   serialNr = 0;

   // DBusMessage
   DBusMessage     *msg;

   // Dbus Message Iterators - main, array, structure
   DBusMessageIter iter,
                   arr,
                   strct;

   // Connection
   DBusConnection  *conn;

   gchar buffer[BUFF_SIZE_SMALL];
   const char *buff = buffer;

   if( NULL == self )
   {
     return false;
   }

   conn = self->m_conn;
   assert( NULL != conn );

   // create a signal and check for errors
   msg = dbus_message_new_signal( "/myObj",
                                  "my.test.Interface",
                                  "arrOfStructSignal" );
   if (NULL == msg)
   {
     return false;
   }

   dbus_message_iter_init_append( msg, &iter );

   // open the array of structures
   dbus_message_iter_open_container( &iter,
                                     DBUS_TYPE_ARRAY,
                                     "r",
&arr );

    cout << "-------------------PASSED_0 " <<  endl;

   // array of 10 structures a(ss)  - for test
   for( int i = 0; i < 10; i++ )
   {

     cout << "-------------------PASSED_1 " <<  endl;

     // Open the a structure within an array
     // Here run-time error  !!!!!!!!!!!!!!!!!!!
     dbus_message_iter_open_container( &arr,
                                       DBUS_TYPE_STRUCT,
                                       NULL,
&strct );

     cout << "-------------------PASSED_2 " <<  endl;

     memset( buffer, 0, BUFF_SIZE_SMALL );
     sprintf(buffer, "test 0 %d", i );

     // append first string to the structure
     if( !dbus_message_iter_append_basic(&strct, DBUS_TYPE_STRING, &buff) )
     {
       dbus_message_unref(msg);
       return false;
     }

     cout << "-------------------PASSED_3 " <<  endl;

     memset( buffer, 0, BUFF_SIZE_SMALL );
     sprintf(buffer, "test 0 %d", i );

     // append second string to the structure
     if( !dbus_message_iter_append_basic(&strct, DBUS_TYPE_STRING, &buff) )
     {
       dbus_message_unref(msg);
       return false;
     }

     cout << "-------------------PASSED_4 " <<  endl;

     // close structure container
     dbus_message_iter_close_container( &arr, &strct );
   }

   // close struct container
   dbus_message_iter_close_container( &iter, &arr );

   // send the message and flush the connection
   if( !dbus_connection_send(conn, msg, &serialNr))
   {
     dbus_message_unref(msg);
     return false;
   }
   dbus_connection_flush(conn);

   // free the message
   dbus_message_unref(msg);

   return true;
}

Thanks for your help

regards,

Bogdan








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