[ns] how to measure the size of received packet

[sasan zhalehpour]

hi,
i want to add a code in ns2.33(mac802.11.cc) to measure the size of the
received packet . i mean i want to put the size of the received or
transmitted packet in a variable and compare it with other parameters such
as DIFS, CW_ ,... in mac802.11cc   .(if  size of packet>Function(CW_) {...})
thx in advance.
sasan