array declaration in class of header file

Question

I need help for my simulation.

Provided first is the initial statement to create a network packet in my main.cc file.

 Ptr<Name> nameWithSequence = Create<Name> (m_interestName); //create value /prefix
 nameWithSequence->appendSeqNum (seq); //append sequence number to /prefix,eg - 0
 Ptr<Interest> interest = Create<Interest> (); //create packet
 interest->SetName                (nameWithSequence); //create name of packet as /prefix0

I wanted to set the network packet to have two values which is consist of name /prefix0 and /prefix1 in one packet so ~ believe array suited well.

Here are the changes that I made

  Ptr<Name> nameWithSequence = Create<Name> (m_interestName); //create value /prefix
  nameWithSequence->appendSeqNum (seq); //append sequence number to /prefix,eg - 0
  Ptr<Name> nameWithNextSequence = Create<Name> (m_interestName); //create value /prefix
 nameWithNextSequence->appendSeqNum ((seq)+1)); //append next sequence number to /prefix,eg - 1

  Ptr<Interest> interest = Create<Interest> (); //create packet
  interest->SetName [0]                (nameWithSequence); //create name of packet as /prefix0
 interest->SetName [1]                (nameWithNextSequence); //create name of packet as /prefix1

it refer to header file as follows:

/**
   * \brief Set interest name
   *
   * @param name smart pointer to Name
   *
   **/
  void
  SetName (Ptr<Name> name);

  /**
   * \brief Another variant to set interest name
   *
   * @param name const reference to Name object
   *
   **/
  void
  SetName (const Name &name);

the code below is extracted from cc file

Interest::Interest (Ptr<Packet> payload/* = Create<Packet> ()*/)
  : m_name ()

Interest::Interest (const Interest &interest)
  : m_name             (Create<Name> (interest.GetName ()))

void
Interest::SetName (Ptr<Name> name)
{
  m_name = name;
  m_wire = 0;
}

void
Interest::SetName (const Name &name)
{
  m_name = Create<Name> (name);
  m_wire = 0;
}

I believe I should declare the array first but I have no idea where should I put the declaration, is it in cc or header or both and how? I think the array name is SetName [2].

Please advise on how to do that.

I'm sorry if I'm presuming too much, but I don't think that you would be able to do that. This is in no way meant to be an insult. It is relatively easy to change the shown code to have an array of "names", but that change might cause other parts of the code to malfunction and break in indeterminable ways (from the above code.) And you don't seem to have enough experience to deal with that if it happens. I think you should find the people who wrote that library/system/whatever that you are already using and ask them to make the change. I'm going to post an answer below anyways. — yzt
– yzt, Commented Jan 8, 2014 at 5:37
hi @yzt. it is ok (still learning anyway ;))..im happy if you could provide me some hint..thanks — user3085445
– user3085445, Commented Jan 8, 2014 at 5:51

yzt · Accepted Answer · 2014-01-08 08:12:38Z

1

The syntax you are using to have an array does not do what you think it does, at all. Here are the changes you have to make to get two names, instead of one. If you want a variable number of names, then you have to do things slightly differently.

Warning: This change might (and probably will) cause compile errors and runtime errors. It is impossible to say where and how without knowing the library you are using. To deal with this, you have to read that code, understand how it works, and analyze what needs to be done to make this small change you want.

Anyways, here it goes. You haven't posted a crucial part of the header, and that's variable declarations for m_name.)

I'm assuming it looks something like this:

Ptr<Name> m_name;

You have to change that to:

Ptr<Name> m_names [2];  // Note the change in name

Then, you change the function declarations (in the header) to:

void SetName (unsigned which, Ptr<Name> name);
void SetName (unsigned which, const Name &name);

and correspondingly, change the implementations in the source file to:

void Interest::SetName (unsigned which, Ptr<Name> name)
{
    if (which < 2)
    {
        m_names[which] = name;
        m_wire = 0; // I don't know what this is.
    }
}

void Interest::SetName (unsigned which, const Name &name)
{
    if (which < 2)
    {
        m_names[which] = Create<Name> (name);
        m_wire = 0;
    }
}

The way you call this is like this (in your main file):

interest->SetName (0, nameWithSequence);
interest->SetName (1, nameWithNextSequence);

The changes I've made will cause compile errors in other parts of the code you are using. This is a good thing. If you can resolve those build problems meaningfully and intelligently, it means you probably understand enough about the system you are using to make small changes to it.

Good luck!

edited Jan 8, 2014 at 8:12

answered Jan 8, 2014 at 5:52

yzt

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5 Comments

user3085445 Over a year ago

thanks @yzt. i had tried it and as you said it cause error but i will dig into it later. The other error (no matching function for call to ‘ns3::ndn::Interest::SetName(ns3::Ptr<ns3::ndn::Name>)’ ../src/ndnSIM/model/wire/ndnsim.cc:171:51: note: candidates are: ./ns3/ndn-interest.h:65:3: note: void ns3::ndn::Interest::SetName(unsigned int, ns3::Ptr<ns3::ndn::Name>) ./ns3/ndn-interest.h:65:3: note: candidate expects 2 arguments, 1 provided. do i have to change anything in main cc file?

yzt Over a year ago

I forgot that. Check the last code section I added to my answer.

user3085445 Over a year ago

@yzt.. can you suggest me how to create variable number of names. appreciate if you could help

yzt Over a year ago

@user3085445: Instead of Ptr<Name> m_names [2];, use a vector like this: std::vector<Ptr<Name>> m_names;. But you need to know a little more C++ to be able to accomplish all this.

user3085445 Over a year ago

sorry to ask again..what about the declaration of the first four line extracted from cc file @yzt

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