[ndnSIM] Modify/Read payload content & Read the content in cache

[Kanin Assantachai]

Dear Alex / Spyridon,

Currently I am working with various parts of the simulator (version 1.1) 
related to its caching mechanism. I need your kind help for the 
following questions.

1. I would like to modify the payload of packets sent by the producer 
app. My current approach is to change this part of code in the 
OnInterest() function of ndn-producer.cc:

Ptr<Data> data = Create<Data> (Create<Packet> (m_virtualPayloadSize));

to

std::string string = "Hello";
Ptr<Data> data = Create<Data> (Create<Packet> (reinterpret_cast<const 
uint8_t*>(&string[0]), 5));

I want to firstly check if this simple way works. Even though the code 
is compiled without an error, I have a difficulty checking whether the 
payload of the packet really carries this string "Hello". So far, I add 
this code to the OnData() function of ndn-consumer.cc to try to read the 
content of the payload:

data->GetPayload ()->Print (std::cout);

It only outputs the size of the payload in the terminal. I have tried 
reading this previous archive about reading the content of payload but 
still cannot solve this problem: 
http://www.lists.cs.ucla.edu/pipermail/ndnsim/2015-January/001501.html
In summary, my questions are whether my simple method in adding a 
specific string to the payload works, and which function (or other 
approach) can I use to really see the real content (string) of the payload?

2. I would like to get the latest content which has just been added to 
the LRU cache. So in the file "lru-policy.h", after this line of code in 
the insert() function:

policy_container::push_back (*item);

I tried adding this line of code to read the newly added content:

std::cout << "Item added: " << policy_container::end 
()->payload()->GetName() << std::endl;

When I compile the file, I get an error saying that the compiler cannot 
recognize the GetName() function. I wonder if I need to #include other 
files. My reference is this archive: 
http://www.lists.cs.ucla.edu/pipermail/ndnsim/2014-July/001329.html

Thank you for your help in advance.

Sincerely,

Kanin Assantachai