97 lines
4.7 KiB
Ada
97 lines
4.7 KiB
Ada
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------------------------------------------------------------------------------
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-- --
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-- GNAT LIBRARY COMPONENTS --
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-- --
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-- G N A T . B O U N D E D _ M A I L B O X E S --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 2003-2020, AdaCore --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
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-- --
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------------------------------------------------------------------------------
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-- This package provides a thread-safe asynchronous communication facility
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-- in the form of mailboxes. Individual mailbox objects are bounded in size
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-- to a value specified by their Capacity discriminants.
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-- Mailboxes actually hold references to messages, not the message values
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-- themselves.
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-- Type Mailbox is defined explicitly as a protected type (via derivation
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-- from a protected type) so that clients may treat them accordingly (for
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-- example, by making conditional/timed entry calls).
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with System;
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with GNAT.Bounded_Buffers;
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generic
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type Message (<>) is limited private;
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type Message_Reference is access all Message;
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-- Mailboxes hold references to Message values, of this type
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package GNAT.Bounded_Mailboxes is
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pragma Preelaborate;
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package Message_Refs is
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new GNAT.Bounded_Buffers (Message_Reference);
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type Mailbox is new Message_Refs.Bounded_Buffer;
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-- Type Mailbox has two inherited discriminants:
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-- Capacity : Positive;
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-- Capacity is the maximum number of Message references
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-- possibly contained at any given instant.
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-- Ceiling : System.Priority;
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-- Users must specify the ceiling priority for the object.
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-- If the Real-Time Systems Annex is not in use this value
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-- is not important.
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-- Protected type Mailbox has the following inherited interface:
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-- entry Insert (Item : Message_Reference);
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-- Insert Item into the Mailbox. Blocks caller
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-- until space is available.
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-- entry Remove (Item : out Message_Reference);
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-- Remove next available Message_Reference from Mailbox.
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-- Blocks caller until a Message_Reference is available.
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-- function Empty return Boolean;
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-- Returns whether the Mailbox contains any Message_References.
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-- Note: State may change immediately after call returns.
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-- function Full return Boolean;
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-- Returns whether any space remains within the Mailbox.
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-- Note: State may change immediately after call returns.
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-- function Extent return Natural;
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-- Returns the number of Message_Reference values currently held
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-- within the Mailbox.
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-- Note: State may change immediately after call returns.
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Default_Ceiling : constant System.Priority := Message_Refs.Default_Ceiling;
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-- A convenience value for the Ceiling discriminant
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end GNAT.Bounded_Mailboxes;
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