code: protected int decodeMandatoryParameters(ISUPParameterFactory parameterFactory, byte[] b, int index)
              throws ParameterException {
  
          int localIndex = index;
          index += super.decodeMandatoryParameters(parameterFactory, b, index);
          if (b.length - index > 1) {
              try {
                  byte[] eventInformation = new byte[1];
                  eventInformation[0] = b[index++];
  
                  EventInformation _ei = parameterFactory.createEventInformation();
                  ((AbstractISUPParameter) _ei).decode(eventInformation);
                  this.setEventInformation(_ei);
              } catch (Exception e) {
                  // AIOOBE or IllegalArg
                  throw new ParameterException("Failed to parse EventInformation due to: ", e);
              }
  
              return index - localIndex;
          } else {
              throw new ParameterException("byte[] must have atleast four octets");
          }
      }
docs: /*
  (non-Javadoc)
  
  @see org.restcomm.protocols.ss7.isup.ISUPMessageImpl#decodeMandatoryParameters (byte[], int)