code: public Tuple getNext() throws IOException
      {
          try
          {
              // load the next pair
              if (!reader.nextKeyValue())
                  return null;
  
              CfInfo cfInfo = getCfInfo(loadSignature);
              CfDef cfDef = cfInfo.cfDef;
              Row row = reader.getCurrentValue();
              Tuple tuple = TupleFactory.getInstance().newTuple(cfDef.column_metadata.size());
              Iterator<ColumnDef> itera = cfDef.column_metadata.iterator();
              int i = 0;
              while (itera.hasNext())
              {
                  ColumnDef cdef = itera.next();
                  ByteBuffer columnValue = row.getBytesUnsafe(ByteBufferUtil.string(cdef.name.duplicate()));
                  if (columnValue != null)
                  {
                      Cell cell = new BufferCell(CellNames.simpleDense(cdef.name), columnValue);
                      AbstractType<?> validator = getValidatorMap(cfDef).get(cdef.name);
                      setTupleValue(tuple, i, cqlColumnToObj(cell, cfDef), validator);
                  }
                  else
                      tuple.set(i, null);
                  i++;
              }
              return tuple;
          }
          catch (InterruptedException e)
          {
              throw new IOException(e.getMessage());
          }
      }
docs: get next row