Re: Requeue

[Darren New <dnew@san.rr.com>]

Anatoly Chernyshev wrote:
> Could someone post a simple yet practical example of using that
> statement in Ada programming?

Part of the need for requeue comes from the fact that a guard can't be
based on the parameters of the call. So if I want to do something like

  entry Save_In_Buffer(Octets : in Stream_Element_Array) 
    when Octets'Length < My_Buffer.Remaining_Space is
  begin .... end Save_In_Buffer;

I can't do that. Octets'Length isn't allowed in the guard.
So instead I do
  entry Save_In_Buffer(...)
    when True is
  begin
    if My_Buffer.Remaining_Space < Octets'Length then
      requeue Save_Wait
    end if;
    ...
  end Save_In_Buffer;

Then Save_Wait has a guard that is gets set to false whenever I put
something into the buffer and true whenever I take something out. Inside
Save_Wait, once you get in, you check again, and if there's still no
room, you requeue once again. Ugly but it works.

I'd be happy to put the code somewhere if you want to look.

-- 
Darren New 
San Diego, CA, USA (PST). Cryptokeys on demand.
      Remember, drive defensively if you drink.