File : pragmarc-queue_bounded_blocking.ads
-- PragmAda Reusable Component (PragmARC)
-- Copyright (C) 2002 by PragmAda Software Engineering. All rights reserved.
-- **************************************************************************
--
-- Bounded queue ADT for concurrent use only
-- Each queue has a preset maximum size
-- A call to Put when the queue is full blocks the caller until another task calls Get
-- A call to Get when the queue is empty blocks the caller until another task calls Put
--
-- History:
-- 2002 Oct 01 J. Carter V1.3--Added Context to Iterate; use mode out to allow scalars
-- 2001 Dec 01 J. Carter V1.2--Added Ceiling_Priority to Handle
-- 2001 Jun 01 J. Carter V1.1--Added Peek
-- 2000 May 01 J. Carter V1.0--Initial release
--
with PragmARC.Queue_Bounded_Unprotected;
with System;
generic -- PragmARC.Queue_Bounded_Blocking
type Element is limited private;
with procedure Assign (To : out Element; From : in Element) is <>;
package PragmARC.Queue_Bounded_Blocking is
pragma Preelaborate;
package Implementation is new PragmARC.Queue_Bounded_Unprotected (Element => Element, Assign => Assign);
type Context_Data is tagged null record; -- Used to provide context data to iterate.
type Action_Ptr is access procedure (Item : in out Element; Context : in out Context_Data'Class; Continue : out Boolean);
-- Since we can't have generic protected subprograms, we use this type for Iterate.
-- This means the actual procedure passed to Iterate must be declared at the library level to pass accessibility checks
protected type Handle (Max_Size : Positive; Ceiling_Priority : System.Any_Priority) is
pragma Priority (Ceiling_Priority);
procedure Clear;
-- Empties the queue; anything on the queue is lost; the queue is initially empty
--
-- Time: O(1)
entry Put (Item : in Element);
-- Adds Item to the tail of the queue
-- If the queue is full, the caller is blocked until another task calls Get
--
-- Time: O(1)
--
-- Barrier: not Is_Full
--
-- Postcondition: not Is_Empty
entry Get (Item : out Element);
-- Removes the next Element from the head of the queue and returns it in Item
-- If the queue is empty, the caller is blocked until another task calls Put
--
-- Time: O(1)
--
-- Barrier: not Is_Empty
--
-- Postcondition: not Is_Full
function Full return Boolean;
-- Returns True if the queue is full; False otherwise
--
-- Time: O(1)
function Empty return Boolean;
-- Returns True if the queue is empty; False otherwise
--
-- Time: O(1)
function Length return Natural;
-- Returns the number of Elements in the queue
--
-- Time: O(1)
function Peek return Element;
-- Returns the Element at the head of the queue without altering the queue
-- Raises Empty if the queue is empty
--
-- Time: O(1)
--
-- Precondition: not Is_Empty raise Empty if violated
procedure Iterate (Action : in Action_Ptr; Context : in out Context_Data'Class);
-- Applies Action to each Element in the queue in turn, from head to tail.
-- Iterate returns immediately if Action sets Continue to False (remainder of the queue is not processed)
private -- Handle
Queue : Implementation.Handle (Max_Size);
end Handle;
end PragmARC.Queue_Bounded_Blocking;
--
-- This is free software; you can redistribute it and/or modify it under
-- terms of the GNU General Public License as published by the Free Software
-- Foundation; either version 2, or (at your option) any later version.
-- This software 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. 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