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-- --
-- --
-- --
-- S p e c --
-- --
-- Copyright (C) 2011-2021, Free Software Foundation, Inc. --
-- --
-- This specification is derived from the Ada Reference Manual for use with --
-- GNAT. The copyright notice above, and the license provisions that follow --
-- apply solely to the contents of the part following the private keyword. --
-- --
-- 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 3, 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 --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <>. --
-- --
-- This unit was originally developed by Matthew J Heaney. --
with System;
with Ada.Containers.Ordered_Sets;
with Ada.Containers.Synchronized_Queue_Interfaces;
with package Queue_Interfaces is
new Ada.Containers.Synchronized_Queue_Interfaces (<>);
type Queue_Priority is private;
with function Get_Priority
(Element : Queue_Interfaces.Element_Type) return Queue_Priority is <>;
with function Before
(Left, Right : Queue_Priority) return Boolean is <>;
Default_Ceiling : System.Any_Priority := System.Priority'Last;
package Ada.Containers.Unbounded_Priority_Queues is
pragma Annotate (CodePeer, Skip_Analysis);
pragma Preelaborate;
package Implementation is
-- All identifiers in this unit are implementation defined
pragma Implementation_Defined;
-- We use an ordered set to hold the queue elements. This gives O(lg N)
-- performance in the worst case for Enqueue and Dequeue.
-- Sequence_Number is used to distinguish equivalent items. Each Enqueue
-- uses a higher Sequence_Number, so that a new item is placed after
-- already-enqueued equivalent items.
-- At any time, the first set element is the one to be dequeued next (if
-- the queue is not empty).
type Set_Elem is record
Sequence_Number : Count_Type;
Item : Queue_Interfaces.Element_Type;
end record;
function "=" (X, Y : Queue_Interfaces.Element_Type) return Boolean is
(not Before (Get_Priority (X), Get_Priority (Y))
and then not Before (Get_Priority (Y), Get_Priority (X)));
-- Elements are equal if neither is Before the other
function "=" (X, Y : Set_Elem) return Boolean is
(X.Sequence_Number = Y.Sequence_Number and then X.Item = Y.Item);
-- Set_Elems are equal if the elements are equal, and the
-- Sequence_Numbers are equal. This is passed to Ordered_Sets.
function "<" (X, Y : Set_Elem) return Boolean is
(if X.Item = Y.Item
then X.Sequence_Number < Y.Sequence_Number
else Before (Get_Priority (X.Item), Get_Priority (Y.Item)));
-- If the items are equal, Sequence_Number breaks the tie. Otherwise,
-- use Before. This is passed to Ordered_Sets.
pragma Suppress (Container_Checks);
package Sets is new Ada.Containers.Ordered_Sets (Set_Elem);
end Implementation;
use Implementation, Implementation.Sets;
protected type Queue (Ceiling : System.Any_Priority := Default_Ceiling)
Priority => Ceiling
is new Queue_Interfaces.Queue with
overriding entry Enqueue (New_Item : Queue_Interfaces.Element_Type);
overriding entry Dequeue (Element : out Queue_Interfaces.Element_Type);
-- The priority queue operation Dequeue_Only_High_Priority had been a
-- protected entry in early drafts of AI05-0159, but it was discovered
-- that that operation as specified was not in fact implementable. The
-- operation was changed from an entry to a protected procedure per the
-- ARG meeting in Edinburgh (June 2011), with a different signature and
-- semantics.
procedure Dequeue_Only_High_Priority
(At_Least : Queue_Priority;
Element : in out Queue_Interfaces.Element_Type;
Success : out Boolean);
overriding function Current_Use return Count_Type;
overriding function Peak_Use return Count_Type;
Q_Elems : Set;
-- Elements of the queue
Max_Length : Count_Type := 0;
-- The current length of the queue is the Length of Q_Elems. This is the
-- maximum value of that, so far. Updated by Enqueue.
Next_Sequence_Number : Count_Type := 0;
-- Steadily increasing counter
end Queue;
end Ada.Containers.Unbounded_Priority_Queues;