| ------------------------------------------------------------------------------ |
| -- -- |
| -- GNAT LIBRARY COMPONENTS -- |
| -- -- |
| -- ADA.CONTAINERS.UNBOUNDED_PRIORITY_QUEUES -- |
| -- -- |
| -- 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 -- |
| -- or FITNESS FOR A PARTICULAR PURPOSE. -- |
| -- -- |
| -- 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 -- |
| -- <http://www.gnu.org/licenses/>. -- |
| -- -- |
| -- This unit was originally developed by Matthew J Heaney. -- |
| ------------------------------------------------------------------------------ |
| |
| with System; |
| with Ada.Containers.Ordered_Sets; |
| with Ada.Containers.Synchronized_Queue_Interfaces; |
| |
| generic |
| 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) |
| with |
| 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; |
| |
| private |
| 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; |
