------------------------------------------------------------------------------ -- -- -- 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 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 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 : in 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;