File : asl-semaphore-counting.ads
-- The Ada Structured Library - A set of container classes and general
-- tools for use with Ada95.
-- Copyright (C) 1998-1999 Corey Minyard (minyard@acm.org)
--
-- This library is free software; you can redistribute it and/or modify it
-- under the terms of the GNU General Public License as published by the
-- Free Software Foundation; either version 2 of the License, or (at your
-- option) any later version.
--
-- This library is distributed in the hope that it will be useful, but
-- WITHOUT 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 along
-- with this library; if not, write to the Free Software Foundation, Inc.,
-- 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.
--
-- A standard counting semaphore. The initial count is specified when the
-- semaphore is declared. The Take operation will block is the count is
-- zero, otherwise Take will decremenet the count. Give will always
-- increment the count.
package Asl.Semaphore.Counting is
type Object (Initial_Count : Natural) is
new Asl.Semaphore.Object with private;
type Object_Ptr is access all Object;
-- Claim the semaphore. Will block until the semaphore is available.
procedure Take (O : in out Object);
-- Release the semaphore.
procedure Give (O : in out Object);
-- Try to take the semaphore, but return an error if not successful.
-- Returns True if the semaphore was claimed and False if not. This
-- will wait up to Timeout time for the semaphore to become available.
procedure Try_To_Take (O : in out Object;
Success : out Boolean;
Timeout : in Duration := 0.0);
private
protected type Mutex (Initial_Count : Natural) is
entry Wait;
procedure Release;
private
Count : Natural := Initial_Count;
end Mutex;
type Object (Initial_Count : Natural) is
new Asl.Semaphore.Object with record
The_Mutex : Mutex(Initial_Count);
end record;
end Asl.Semaphore.Counting;