vhdl - VHDL 保护类型数组

Question

我试图更好地使用 VHDL protected 类型，所以我将以下测试放在一起(当然只是为了说明 - 我的实际用例要复杂得多):

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;

这编译。但是，以下行不会:

type prot_type1_array is array (natural range <>) of prot_type1;

Ashenden 说(第 3 版，第 589 页)“ protected 类型不能用作……复合类型的元素”。这很不幸。我希望能够用 body 创建另一个 protected 类型:

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;

并避免重复 prot_type1.set() 中的代码(这在这种情况下是微不足道的，但在我的实际用例中会复杂得多)。不过，我唯一的选择似乎是 (1) 基本上重写整个 prot_type1，除了我的私有(private)变量的数组类型。或者 (2)，在内部展平数组，例如:

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;

这行得通，但对于小型阵列来说有点不受欢迎，而且对于大型阵列来说极度不受欢迎。还有别的办法吗？

Answer 1

这是基于 Morten Zilmer 评论的建议。 prot1_type 可以访问整数而不是唯一整数。我使用函数 append、remove 和 get 来管理整数值。

代码如下:

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;