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+------------------------------------------------------------------------------
+-- --
+-- GNAT LIBRARY COMPONENTS --
+-- --
+-- G N A T . B O U N D E D _ B U F F E R 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). --
+-- --
+------------------------------------------------------------------------------
+
+-- This package provides a thread-safe generic bounded buffer abstraction.
+-- Instances are useful directly or as parts of the implementations of other
+-- abstractions, such as mailboxes.
+
+-- Bounded_Buffer is declared explicitly as a protected type, rather than as
+-- a simple limited private type completed as a protected type, so that
+-- clients may make calls accordingly (i.e., conditional/timed entry calls).
+
+with System;
+
+generic
+ type Element is private;
+ -- The type of the values contained within buffer objects
+
+package GNAT.Bounded_Buffers is
+ pragma Pure;
+
+ type Content is array (Positive range <>) of Element;
+ -- Content is an internal artefact that cannot be hidden because protected
+ -- types cannot contain type declarations.
+
+ Default_Ceiling : constant System.Priority := System.Default_Priority;
+ -- A convenience value for the Ceiling discriminant
+
+ protected type Bounded_Buffer
+ (Capacity : Positive;
+ -- Objects of type Bounded_Buffer specify the maximum number of Element
+ -- values they can hold via the discriminant Capacity.
+
+ 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.
+ is
+ pragma Priority (Ceiling);
+
+ entry Insert (Item : Element);
+ -- Insert Item into the buffer, blocks caller until space is available
+
+ entry Remove (Item : out Element);
+ -- Remove next available Element from buffer. Blocks caller until an
+ -- Element is available.
+
+ function Empty return Boolean;
+ -- Returns whether the instance contains any Elements.
+ -- Note: State may change immediately after call returns.
+
+ function Full return Boolean;
+ -- Returns whether any space remains within the instance.
+ -- Note: State may change immediately after call returns.
+
+ function Extent return Natural;
+ -- Returns the number of Element values currently held
+ -- within the instance.
+ -- Note: State may change immediately after call returns.
+
+ private
+ Values : Content (1 .. Capacity);
+ -- The container for the values held by the buffer instance
+
+ Next_In : Positive := 1;
+ -- The index of the next Element inserted. Wraps around
+
+ Next_Out : Positive := 1;
+ -- The index of the next Element removed. Wraps around
+
+ Count : Natural := 0;
+ -- The number of Elements currently held
+ end Bounded_Buffer;
+
+end GNAT.Bounded_Buffers;