Pointer to a Pointer


A customer asked me whether it was possible to have a pointer to a pointer in VHDL. In other words, is it possible to have an access type that points to another access type?

I did a little experiment on EDA Playground and it turns out that it is.

Here's an access type to an integer:

    type ai is access integer;

and here's an access type to that access type:

    type aai is access ai;

and here are variables to both:

    variable aiv : ai;
    variable aaiv : aai;

So, let's allocate memory for both:

    aiv := new integer'(6);
    aaiv:= new ai'(aiv);

and then dereference each:

    report "aiv.all= " & integer'image(aiv.all);
    report "aaiv.all.all= " & integer'image(aaiv.all.all);

Yes, aaiv.all.all !

Here's all the code and the EDA Playground link:

https://www.edaplayground.com/x/4USx

entity E is
end entity ;

 architecture A of E is
begin

   process
    type ai is access integer;
    type aai is access ai;
    variable aiv : ai;
    variable aaiv : aai;
  begin
    aiv := new integer'(6);
    aaiv:= new ai'(aiv);
    report "aiv.all= " & integer'image(aiv.all);
    report "aaiv.all.all= " & integer'image(aaiv.all.all);
    wait;
  end process;

 end architecture A;

A customer asked me about this. I didn't know the answer, so I wrote a few lines of code on EDA Playground. EDA Playground is great for that, because it's always on. You don't have to queue for licences, wait for EDA tools to start, create new files, fire up editors...

Comments

  1. Shankar Shiva3 December 2018 at 16:17

    thanks and it is awesome !

    ReplyDelete
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