Re: [ns] HOW TO ACCESS C++ VARIABLE USING TCL (fwd)

[shailesh sheoran <shailesh@ece.ubc.ca>]

 this is exactly what i am doing. 

 i need to access the class variable "tapbytes_" from .tcl.
 so i have done following modifications to the 
 TapAgentClass:
static class TapAgentClass : public TclClass {
 protected:
        
        // MY MODIFICATION 
        virtual void bind();
        virtual int method(int argc, const char*const* argv);
        static int tapbytes_;	
 
 public:
	// MY MODIFICATION
	void recordbytes(Packet* );

	TapAgentClass() : TclClass("Agent/Tap"),tapbytes_(0) {}
	TclObject* create(int, const char*const*) {
		return (new TapAgent());
	}

  then i go on to define recordbytes();
  and i define bind() and method() as follows:


void TapAgentClass::bind()
{
        // Call to base class bind() must precede add_method() 
        TclClass::bind();
        add_method("tapbytes");
}
int TapAgentClass::method(int ac, const char*const* av)
{
        Tcl& tcl = Tcl::instance();
        // Notice this argument translation; we can then handle them 
//as if in TclObject::command() 
        int argc = ac - 2;
        const char*const* argv = av + 2;
        if (argc == 2) {
                if (strcmp(argv[1], "tapbytes") == 0) {
                        tcl.resultf("%d", tapbytes_);
                        return (TCL_OK);
                }
        } else if (argc == 3) {
                if (strcmp(argv[1], "tapbytes") == 0) {
                        tapbytes_ = atoi(argv[2]);
                        return (TCL_OK);
                }
        }
        return TclClass::method(ac, av);
}



are there any obvious problems with this code? i get the error:
Undefined Symbol "TapAgentClass::tapbytes_" referenced from text.

now if i define tapbytes_ to be global. then it compiles but while running
in the .tcl script i CAN"T do the following:

set agent2 [new Agent/Tap]
$agent2 tapbytes

could someone be kind enough to look into this long code. i would really
appreciate it.


Shailesh Sheoran
M.ASc. 
Department of Electrical Engineering
University of British Columbia

---------- Forwarded message ----------
Date: Mon, 15 Jan 2001 13:59:12 -0800
From: Scott Michel <scottm@cs.ucla.edu>
To: shailesh sheoran <shailesh@ece.ubc.ca>
Subject: Re: [ns] HOW TO ACCESS C++ VARIABLE USING TCL

On Sun, Jan 14, 2001 at 10:16:52PM -0800, shailesh sheoran wrote:
> hi,
>   i needed to define a variable in tap.cc and access it from my  .tcl
> script. i couldnot quite decipher the information from the manual. would
> someone please tell me how to do it.
>   i would really appreciate it.
> thanks,
> Shailesh Sheoran
> M.ASc. 
> Department of Electrical Engineering
> University of British Columbia

G'day, eh?!

All seriousness aside, is the C++ variable a class variable or an
instance variable?

- For class variables (i.e. "static" in the class declaration), you
  want to call bind(...).

- For instance variables (i.e. variables in each instance), you want
  to look at examples that use "delay_bind(...)", which abound in the
  code. Have a look at agent.cc, as one example.

HTH


-scooter