Abstract cast

[Logger]

I have an application where I have two objects, the only thing I know for sure is they are both extensions of uvm_object. However, I can do something useful if I know if one is an extension of the other.

It would be nice if uvm_object_wrapper had some kind of is_a() function.

class uvm_object_wrapper;
    virtual function bit is_a_base_of(uvm_object obj);
        // macro generated extension would implement a $cast() to test the is_a relationship.
    endfunction
endclass

That way I could find out if the type of Y is an extension of the type of X.

X::type_id.is_a_base_of(Y);

Even better would be an is_a method that can be used like:

Y::type_id.is_a(X);

But I think implementation would be more complicated.

-Ryan

[dave_59]

You probably need to explain what the useful thing you want to do if you did know. There's probably a very different way to approach it.

Also, are you aware of the difference between X.get_object_type() versus classX::get_type()

if you have

ClassX X;

X = ClassX::type_id::create(...);

if (ClassX::get_type() != X.get_object_type()) // then you know X has an object whose type is an extension of ClassX

[Logger]

In my other thread I have a function

function uvm_sequence_item_queue get_completed_items();
      get_completed_items = m_completed_items;
   endfunction:get_completed_items

I wanted it to have a type_filter parameter. So if you passed in a type_filter, rather than returning everything, it would return a filtered subset. Since I didn't figure that out, I create a parameterized helper function that uses $cast to do the test.

This following example should be a little more clear. I have an incomplete function called filter(). What should I put in place of my comment /* x is_a type_filter */?

program test;

import uvm_pkg::*;

class A extends uvm_object;
   `uvm_object_utils(A)
   function new (string name = "A");
      super.new(name);
   endfunction // new
endclass // A

class AA extends A;
   `uvm_object_utils(AA)
   function new (string name = "AA");
      super.new(name);
   endfunction // new
endclass // AA

class B extends uvm_object;
   `uvm_object_utils(
   function new (string name = "B");
      super.new(name);
   endfunction // new
endclass // B

typedef uvm_object uvm_object_queue[$];

function uvm_object_queue filter(const ref uvm_object q[$], input uvm_object_wrapper type_filter);
   filter = q.find(x) with (/* x is_a type_filter */);
endfunction // filter

initial begin
   A a;
   AA aa;
   B b;
   uvm_object o[$];
   uvm_object_wrapper type_filter;
   uvm_object f[$];

   a = new("a");
   o.push_back(a);
   aa = new("aa");
   o.push_back(aa);
   b = new("b");
   o.push_back(;

   // is_a A
   $write("\n\n\n ---- is a A ----\n");
   f = filter(o,A::get_type());
   // should yield two objects in f: a and aa.
   foreach(f[i])
     f[i].print();

   // is_a AA
   $write("\n\n\n ---- is a AA ----\n");
   f = filter(o,AA::get_type());
   // should yield one object in f: aa
   foreach(f[i])
     f[i].print();

   // is_a B
   $write("\n\n\n ---- is a B ----\n");
   f = filter(o,B::get_type());
   // should yield one object in f: b
   foreach(f[i])
     f[i].print();

end


endprogram // test

-Ryan

[dave_59]

This is something that could be added to the factory, but for now you can add this virtual method to your classes

virtual function bit is_a(uvm_object_wrapper am_a);
     if (my_type::get_type() == am_a.get_object_type())
          return 1;
     else
          return super.is_a(am_a);
endfunction

The base class returns false if no match.