how to understand the usage of ”CounterCalculator“ in statistics framework when connect to trace source

[Boyce Field]

Hi, dear ns3 user:

I have difficulty to understand the following code in examples/stats/wifi-example-sim.cc

  Config::Connect ("/NodeList/1/DeviceList/*/$ns3::WifiNetDevice/Mac/MacRx",
                   MakeCallback (&PacketCounterCalculator::PacketUpdate,
                                 totalRx));

I find the MacRx trace source in wifi-mac.cc

    .AddTraceSource ("MacRx",
                     "A packet has been received by this device, has been passed up from the physical layer "
                     "and is being forwarded up the local protocol stack. This is a non-promiscuous trace.",
                     MakeTraceSourceAccessor (&WifiMac::m_macRxTrace),
                     "ns3::Packet::TracedCallback")

and the corresponding m_macRxTrace' signature is

TracedCallback<Ptr<const Packet> > m_macRxTrace;

The signature of PacketUpdate is

void
PacketCounterCalculator::PacketUpdate (std::string path,
                                       Ptr<const Packet> packet)

I know that

1. the 1st arguement path in PacketUpdate is related to the 1st arg in Config::Connect, which may be the context.

2. the 2nd arguement packet in PacketUpdate is what we concerned and we will retrive some infomation from it. when m_macTxTrace(packet), the code we write could be called.

SO:

  Ptr<PacketCounterCalculator> totalRx =
    CreateObject<PacketCounterCalculator>();
  totalRx->SetKey ("wifi-rx-frames");
  totalRx->SetContext ("node[1]");

How to understand when I make a callback from PacketUpdate and totalRx in Config::Connect?

I think only the PacketUpdate is enough, as the first Dataculator eample which I can understand:

  Ptr<CounterCalculator<uint32_t> > totalTx =
    CreateObject<CounterCalculator<uint32_t> >();
  totalTx->SetKey ("wifi-tx-frames");
  totalTx->SetContext ("node[0]");
  Config::Connect ("/NodeList/0/DeviceList/*/$ns3::WifiNetDevice/Mac/MacTx",
                   MakeBoundCallback (&TxCallback, totalTx));
  data.AddDataCalculator (totalTx);