Re: Designing Timers using Ada.Real_Time.Timing_Events package


Dmitry A. Kazakov wrote:
On Mon, 27 Mar 2006 09:49:59 +0200, Dmitry A. Kazakov wrote:

-- Main entrance (is closed during notification) The reason is
-- to aviod irace condition upon timer event. Otherwise a task
-- might get it twice.
entry Wait_For when Inactive or not Occured is
if Inactive then
raise Timer_Canceled;
else
requeue Wait_Notify with abort;
end if;
end Wait_For;

-- The notification queue, this is a private entry point to gather
-- the waiting requests.
entry Wait_Notify when Inactive or Occured is
if Inactive then
raise Timer_Canceled;

I forgot to reset it:

else
Occurred := Wait_Notify'Count > 0;

end if;
end Wait_Notify;

procedure Set (Period : Time_Span) is
begin
-- attach Signal to the timer
Inactive := False;
end Set;

procedure Signal (...) is
Occurred := True;
end Signal;

procedure Stop is
-- detach Signal from the timer
Inactive := True;
end Stop;

Dmitry,

Before going further, I would like to know if this is exactly what you
had in mind. By the way, it is compilable.


with Ada.Real_Time.Timing_Events;

package Dmitry_Timers is

use Ada;

Timer_Canceled : exception;

protected type Periodic_Timer is
entry Wait_For;
-- May raise Timer_Canceled
procedure Set (Period : Real_Time.Time_Span);
-- Sets. reset timer
procedure Cancel;
-- Stops timer. Any task in Wait_For queue gets Timer_Canceled
raised
entry Simulate;
-- Simulates a timer event
private
procedure Signal (Event: in out
Real_Time.Timing_Events.Timing_Event);
-- To be set as a handler for Ada.Real_Time.Timing_Events
-- [...]
-- Some internal entry to requeue Wait_For, if Signal cannot
-- be an entry, but must be a protected procedure, instead.
entry Wait_Notify;

Inactive : Boolean := True;
Occurred : Boolean := False;
The_Event : Real_Time.Timing_Events.Timing_Event;
end Periodic_Timer;

end Dmitry_Timers;

package body Dmitry_Timers is

protected body Periodic_Timer is
entry Wait_For when Inactive or not Occurred is
begin
if Inactive then
raise Timer_Canceled;
else
requeue Wait_Notify with abort;
end if;
end Wait_For;

entry Wait_Notify when Inactive or Occurred is
begin
if Inactive then
raise Timer_Canceled;
else
Occurred := Wait_Notify'Count > 0;
end if;
end Wait_Notify;

procedure Set (Period : Real_Time.Time_Span) is
begin
Real_Time.Timing_Events.Set_Handler (The_Event, Period,
Signal'access);
end Set;

procedure Cancel is
Success : Boolean := False;
use type Ada.Real_Time.Timing_Events.Timing_Event_Handler;
begin
if Real_Time.Timing_Events.Current_Handler (The_Event) /= null
then
Real_Time.Timing_Events.Cancel_Handler (The_Event,
Success);
Inactive := True;
Occurred := False;
end if;
end Cancel;

entry Simulate when True is
begin
null; -- What does it do exactly???
end Simulate;

procedure Signal (Event: in out
Real_Time.Timing_Events.Timing_Event) is
begin
Occurred := True;
-- Action to be performed.
end Signal;

end Periodic_Timer;

end Dmitry_Timers;

AV

.

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