arrays of VHDL protected types - vhdl

Question

I am trying to make better use of VHDL protected types, so I threw together the following test (just for illustration, of course - my actual use case is considerably more complex):
type prot_type1 is protected
procedure set (new_data : integer);
impure function get return integer;
end protected prot_type1;
type prot_type1 is protected body
variable data : integer := 0;
procedure set (new_data : integer) is
begin
data := new_data;
end procedure set;
impure function get return integer is
begin
return data;
end function get;
end protected body prot_type1;
This compiles. However, the following line does not:
type prot_type1_array is array (natural range <>) of prot_type1;
Ashenden says (3rd Ed., p. 589) "Protected types cannot be used as elements of ... composite types". This is unfortunate. I was hoping to be able to create another protected type with the body:
type prot_type2 is protected body
variable data : prot_type1_array(0 to 3);
procedure set (idx : natural; new_data : integer) is
begin
data(idx).set(new_data);
end procedure set;
...
end protected body prot_type2;
and avoid duplicating the code in prot_type1.set() (which is admittedly trivial in this case, but would be much more complex in my actual use case). It seems my only choice, though, is (1) to basically rewrite the entirety of prot_type1 except with an array type for my private variable. Or (2), flatten the array internally, like:
type prot_type2 is protected body
variable data0 : prot_type1;
variable data1 : prot_type1;
procedure set (idx : natural; new_data : integer) is
begin
case idx is
when 0 =>
data0.set(new_data);
when 1 =>
data1.set(new_data);
when others =>
-- handle exceptions here
end case;
end procedure set;
...
end protected body prot_type2;
This works, but is mildly undesirable for small arrays, and is extremely undesirable for large arrays. Is there another way?

Answer 1

here is a suggestion based on Morten Zilmer comment. The prot1_type get an access on integer instead of a unique integer. I have used function append, remove and get to manage the integer values.
Here is the code :
type array_int is array (natural range <>) of integer;
type a_integer is access array_int;
type prot_type1 is protected
-- add a new value at the end of the vector
procedure append (new_data : integer);
-- remove a value from the vector, return 0 ik OK, -1 is the item doesn't exist
impure function remove (index : integer) return integer;
-- return the integer value of the item
impure function get(index : integer) return integer;
end protected prot_type1;
type prot_type1 is protected body
variable data : a_integer;
procedure append(new_data : integer) is
variable temp : a_integer;
begin
-- create a temporary vector with the new values
temp := new array_int'(data.all & new_data);
-- free memory of the real vector
Deallocate(data);
-- reallocate the real vector with the good values
data := new array_int'(temp.all);
-- free memory of the temporary vector
Deallocate(temp);
end procedure append;
impure function remove(index : integer) return integer is
variable temp : a_integer;
begin
if (index > data'length-1 or index < 0) then -- not sure if the vector is (0 to length -1) or (1 to length). to be tested !!!
return -1;
else
-- create a temporary vector with the new values
temp := new array_int'(data(0 to index-1) & data(index+1 to data'length-1));
-- free memory of the real vector
Deallocate(data);
-- reallocate the real vector with the good values
data := new array_int'(temp.all);
-- free memory of the temporary vector
Deallocate(temp);
return 0;
end if;
end function remove;
impure function get(index : integer) return integer is
begin
return data(index);
end function get;
end protected body prot_type1;