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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 Ada Core Technologies, Inc. --
+-- --
+-- 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, 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. --
+-- --
+-- 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). --
+-- --
+------------------------------------------------------------------------------
+
+-- 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 : in 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;