+++ /dev/null
-------------------------------------------------------------------------------
--- --
--- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS --
--- --
--- S Y S T E M . T A S K I N G . A S Y N C _ D E L A Y S --
--- --
--- S p e c --
--- --
--- $Revision: 1.1 $
--- --
--- Copyright (C) 1998-1999 Ada Core Technologies, Inc. --
--- --
--- GNARL is free software; you can redistribute it and/or modify it under --
--- terms of the GNU General Public License as published by the Free Soft- --
--- ware Foundation; either version 2, or (at your option) any later ver- --
--- sion. GNARL is distributed in the hope that it will be useful, but WITH- --
--- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
--- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
--- for more details. You should have received a copy of the GNU General --
--- Public License distributed with GNARL; see file COPYING. If not, write --
--- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
--- MA 02111-1307, USA. --
--- --
--- As a special exception, if other files instantiate generics from this --
--- unit, or you link this unit with other files to produce an executable, --
--- this unit does not by itself cause the resulting executable to be --
--- covered by the GNU General Public License. This exception does not --
--- however invalidate any other reasons why the executable file might be --
--- covered by the GNU Public License. --
--- --
--- GNARL was developed by the GNARL team at Florida State University. It is --
--- now maintained by Ada Core Technologies Inc. in cooperation with Florida --
--- State University (http://www.gnat.com). --
--- --
-------------------------------------------------------------------------------
-
--- This package contains the procedures to implements timeouts (delays) on
--- asynchronous select statements.
-
--- Note: the compiler generates direct calls to this interface, via Rtsfind.
--- Any changes to this interface may require corresponding compiler changes.
-
-package System.Tasking.Async_Delays is
-
- -- Suppose the following source code is given:
-
- -- select delay When;
- -- ...continuation for timeout case...
- -- then abort
- -- ...abortable part...
- -- end select;
-
- -- The compiler should expand this to the following:
-
- -- declare
- -- DB : aliased Delay_Block;
- -- begin
- -- if System.Tasking.Async_Delays.Enqueue_Duration
- -- (When, DB'Unchecked_Access)
- -- then
- -- begin
- -- A101b : declare
- -- procedure _clean is
- -- begin
- -- System.Tasking.Async_Delays.Cancel_Async_Delay
- -- (DB'Unchecked_Access);
- -- return;
- -- end _clean;
- -- begin
- -- abort_undefer.all;
- -- ...abortable part...
- -- exception
- -- when all others =>
- -- declare
- -- E105b : exception_occurrence;
- -- begin
- -- save_occurrence (E105b, get_current_excep.all.all);
- -- _clean;
- -- reraise_occurrence_no_defer (E105b);
- -- end;
- -- at end
- -- _clean;
- -- end A101b;
- -- exception
- -- when _abort_signal =>
- -- abort_undefer.all;
- -- end;
- -- end if;
- --
- -- if Timed_Out (DB'Unchecked_Access) then
- -- ...continuation for timeout case...
- -- end if;
- -- end;
-
- -----------------
- -- Delay_Block --
- -----------------
-
- type Delay_Block is limited private;
- type Delay_Block_Access is access all Delay_Block;
-
- function Enqueue_Duration
- (T : in Duration;
- D : Delay_Block_Access) return Boolean;
- -- Enqueue the specified relative delay. Returns True if the delay has
- -- been enqueued, False if it has already expired.
- -- If the delay has been enqueued, abortion is deferred.
-
- procedure Cancel_Async_Delay (D : Delay_Block_Access);
- -- Cancel the specified asynchronous delay
-
- function Timed_Out (D : Delay_Block_Access) return Boolean;
- pragma Inline (Timed_Out);
- -- Return True if the delay specified in D has timed out
-
- -- There are child units for delays on Ada.Calendar.Time and
- -- Ada.Real_Time.Time, so that an application will not need to link in
- -- features that is not using.
-
-private
-
- type Delay_Block is record
- Self_Id : Task_ID;
- -- ID of the calling task
-
- Level : ATC_Level_Base;
- -- Normally Level is the ATC nesting level of the
- -- async. select statement to which this delay belongs, but
- -- after a call has been dequeued we set it to
- -- ATC_Level_Infinity so that the Cancel operation can
- -- detect repeated calls, and act idempotently.
-
- Resume_Time : Duration;
- -- The absolute wake up time, represented as Duration
-
- Timed_Out : Boolean := False;
- -- Set to true if the delay has timed out
-
- Succ, Pred : Delay_Block_Access;
- -- A double linked list
- end record;
-
- -- The above "overlaying" of Self_ID and Level to hold other
- -- data that has a non-overlapping lifetime is an unabashed
- -- hack to save memory.
-
- procedure Time_Enqueue
- (T : Duration;
- D : Delay_Block_Access);
- pragma Inline (Time_Enqueue);
- -- Used by the child units to enqueue delays on the timer queue
- -- implemented in the body of this package.
-
-end System.Tasking.Async_Delays;
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