gcc/ada/a-cuprqu.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT LIBRARY COMPONENTS                          --
   4 --                                                                          --
   5 --                 ADA.CONTAINERS.UNBOUNDED_PRIORITY_QUEUES                 --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --          Copyright (C) 2011-2016, Free Software Foundation, Inc.         --
  10 --                                                                          --
  11 -- This specification is derived from the Ada Reference Manual for use with --
  12 -- GNAT. The copyright notice above, and the license provisions that follow --
  13 -- apply solely to the  contents of the part following the private keyword. --
  14 --                                                                          --
  15 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  16 -- terms of the  GNU General Public License as published  by the Free Soft- --
  17 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  18 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  19 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  20 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
  21 --                                                                          --
  22 -- As a special exception under Section 7 of GPL version 3, you are granted --
  23 -- additional permissions described in the GCC Runtime Library Exception,   --
  24 -- version 3.1, as published by the Free Software Foundation.               --
  25 --                                                                          --
  26 -- You should have received a copy of the GNU General Public License and    --
  27 -- a copy of the GCC Runtime Library Exception along with this program;     --
  28 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  29 -- <http://www.gnu.org/licenses/>.                                          --
  30 --                                                                          --
  31 -- This unit was originally developed by Matthew J Heaney.                  --
  32 ------------------------------------------------------------------------------
  33
  34 with System;
  35 with Ada.Containers.Ordered_Sets;
  36 with Ada.Containers.Synchronized_Queue_Interfaces;
  37
  38 generic
  39    with package Queue_Interfaces is
  40      new Ada.Containers.Synchronized_Queue_Interfaces (<>);
  41
  42    type Queue_Priority is private;
  43
  44    with function Get_Priority
  45      (Element : Queue_Interfaces.Element_Type) return Queue_Priority is <>;
  46
  47    with function Before
  48      (Left, Right : Queue_Priority) return Boolean is <>;
  49
  50    Default_Ceiling : System.Any_Priority := System.Priority'Last;
  51
  52 package Ada.Containers.Unbounded_Priority_Queues is
  53    pragma Annotate (CodePeer, Skip_Analysis);
  54    pragma Preelaborate;
  55
  56    package Implementation is
  57
  58       --  All identifiers in this unit are implementation defined
  59
  60       pragma Implementation_Defined;
  61
  62       --  We use an ordered set to hold the queue elements. This gives O(lg N)
  63       --  performance in the worst case for Enqueue and Dequeue.
  64       --  Sequence_Number is used to distinguish equivalent items. Each Enqueue
  65       --  uses a higher Sequence_Number, so that a new item is placed after
  66       --  already-enqueued equivalent items.
  67       --
  68       --  At any time, the first set element is the one to be dequeued next (if
  69       --  the queue is not empty).
  70
  71       type Set_Elem is record
  72          Sequence_Number : Count_Type;
  73          Item : Queue_Interfaces.Element_Type;
  74       end record;
  75
  76       function "=" (X, Y : Queue_Interfaces.Element_Type) return Boolean is
  77          (not Before (Get_Priority (X), Get_Priority (Y))
  78             and then not Before (Get_Priority (Y), Get_Priority (X)));
  79       --  Elements are equal if neither is Before the other
  80
  81       function "=" (X, Y : Set_Elem) return Boolean is
  82          (X.Sequence_Number = Y.Sequence_Number and then X.Item = Y.Item);
  83       --  Set_Elems are equal if the elements are equal, and the
  84       --  Sequence_Numbers are equal. This is passed to Ordered_Sets.
  85
  86       function "<" (X, Y : Set_Elem) return Boolean is
  87          (if X.Item = Y.Item
  88             then X.Sequence_Number < Y.Sequence_Number
  89             else Before (Get_Priority (X.Item), Get_Priority (Y.Item)));
  90       --  If the items are equal, Sequence_Number breaks the tie. Otherwise,
  91       --  use Before. This is passed to Ordered_Sets.
  92
  93       pragma Suppress (Container_Checks);
  94       package Sets is new Ada.Containers.Ordered_Sets (Set_Elem);
  95
  96    end Implementation;
  97
  98    use Implementation, Implementation.Sets;
  99
 100    protected type Queue (Ceiling : System.Any_Priority := Default_Ceiling)
 101    with
 102      Priority => Ceiling
 103    is new Queue_Interfaces.Queue with
 104
 105       overriding entry Enqueue (New_Item : Queue_Interfaces.Element_Type);
 106
 107       overriding entry Dequeue (Element : out Queue_Interfaces.Element_Type);
 108
 109       --  The priority queue operation Dequeue_Only_High_Priority had been a
 110       --  protected entry in early drafts of AI05-0159, but it was discovered
 111       --  that that operation as specified was not in fact implementable. The
 112       --  operation was changed from an entry to a protected procedure per the
 113       --  ARG meeting in Edinburgh (June 2011), with a different signature and
 114       --  semantics.
 115
 116       procedure Dequeue_Only_High_Priority
 117         (At_Least : Queue_Priority;
 118          Element  : in out Queue_Interfaces.Element_Type;
 119          Success  : out Boolean);
 120
 121       overriding function Current_Use return Count_Type;
 122
 123       overriding function Peak_Use return Count_Type;
 124
 125    private
 126       Q_Elems : Set;
 127       --  Elements of the queue
 128
 129       Max_Length : Count_Type := 0;
 130       --  The current length of the queue is the Length of Q_Elems. This is the
 131       --  maximum value of that, so far. Updated by Enqueue.
 132
 133       Next_Sequence_Number : Count_Type := 0;
 134       --  Steadily increasing counter
 135    end Queue;
 136
 137 end Ada.Containers.Unbounded_Priority_Queues;