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--                                                                          --

--                         GNAT LIBRARY COMPONENTS                          --

--                                                                          --

--                 G N A T . B O U N D E D _ M A I L B O X E S              --

--                                                                          --

--                                 S p e c                                  --

--                                                                          --

--                     Copyright (C) 2003-2006, AdaCore                     --

--                                                                          --

-- GNAT 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.  GNAT 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 GNAT;  see file COPYING.  If not, write --

-- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --

-- Boston, MA 02110-1301, 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.                                      --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --

--                                                                          --

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--  This package provides a thread-safe asynchronous communication facility

--  in the form of mailboxes. Individual mailbox objects are bounded in size

--  to a value specified by their Capacity discriminants.

--  Mailboxes actually hold references to messages, not the message values

--  themselves.

--  Type Mailbox is defined explicitly as a protected type (via derivation

--  from a protected type) so that clients may treat them accordingly (for

--  example, by making conditional/timed entry calls).

with System;

with GNAT.Bounded_Buffers;

generic

   type Message (<>) is limited private;

   type Message_Reference is access all Message;

   --  Mailboxes hold references to Message values, of this type

package GNAT.Bounded_Mailboxes is

   pragma Preelaborate;

   package Message_Refs is

      new GNAT.Bounded_Buffers (Message_Reference);

   type Mailbox is new Message_Refs.Bounded_Buffer;

   --  Type Mailbox has two inherited discriminants:

   --  Capacity : Positive;

   --     Capacity is the maximum number of Message references

   --     possibly contained at any given instant.

   --  Ceiling : System.Priority;

   --     Users must specify the ceiling priority for the object.

   --     If the Real-Time Systems Annex is not in use this value

   --     is not important.

   --  Protected type Mailbox has the following inherited interface:

   --  entry Insert (Item : Message_Reference);

   --     Insert Item into the Mailbox. Blocks caller

   --     until space is available.

   --  entry Remove (Item : out Message_Reference);

   --     Remove next available Message_Reference from Mailbox.

   --     Blocks caller until a Message_Reference is available.

   --  function Empty return Boolean;

   --     Returns whether the Mailbox contains any Message_References.

   --     Note: State may change immediately after call returns.

   --  function Full return Boolean;

   --     Returns whether any space remains within the Mailbox.

   --     Note: State may change immediately after call returns.

   --  function Extent return Natural;

   --     Returns the number of Message_Reference values currently held

   --     within the Mailbox.

   --     Note: State may change immediately after call returns.

   Default_Ceiling : constant System.Priority := Message_Refs.Default_Ceiling;

   --  A convenience value for the Ceiling discriminant

end GNAT.Bounded_Mailboxes;