1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT LIBRARY COMPONENTS                          --
4--                                                                          --
5--              ADA.CONTAINERS.GENERIC_CONSTRAINED_ARRAY_SORT               --
6--                                                                          --
7--                                 B o d y                                  --
8--                                                                          --
9--          Copyright (C) 2004-2021, Free Software Foundation, Inc.         --
10--                                                                          --
11-- GNAT is free software;  you can  redistribute it  and/or modify it under --
12-- terms of the  GNU General Public License as published  by the Free Soft- --
13-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
14-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
15-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
16-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
17--                                                                          --
18-- As a special exception under Section 7 of GPL version 3, you are granted --
19-- additional permissions described in the GCC Runtime Library Exception,   --
20-- version 3.1, as published by the Free Software Foundation.               --
21--                                                                          --
22-- You should have received a copy of the GNU General Public License and    --
23-- a copy of the GCC Runtime Library Exception along with this program;     --
24-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
25-- <http://www.gnu.org/licenses/>.                                          --
26--                                                                          --
27-- This unit was originally developed by Matthew J Heaney.                  --
28------------------------------------------------------------------------------
29
30--  This algorithm was adapted from GNAT.Heap_Sort_G (see g-hesorg.ad[sb])
31
32procedure Ada.Containers.Generic_Constrained_Array_Sort
33  (Container : in out Array_Type)
34is
35   subtype T is Long_Long_Integer;
36
37   function To_Index (J : T) return Index_Type;
38   pragma Inline (To_Index);
39
40   procedure Sift (S : T);
41
42   A : Array_Type renames Container;
43
44   --------------
45   -- To_Index --
46   --------------
47
48   function To_Index (J : T) return Index_Type is
49      K : constant T'Base := Index_Type'Pos (A'First) + J - T'(1);
50   begin
51      return Index_Type'Val (K);
52   end To_Index;
53
54   Max  : T := A'Length;
55   Temp : Element_Type;
56
57   ----------
58   -- Sift --
59   ----------
60
61   procedure Sift (S : T) is
62      C   : T := S;
63      Son : T;
64
65   begin
66      loop
67         Son := 2 * C;
68
69         exit when Son > Max;
70
71         declare
72            Son_Index : Index_Type := To_Index (Son);
73
74         begin
75            if Son < Max then
76               if A (Son_Index) < A (Index_Type'Succ (Son_Index)) then
77                  Son := Son + 1;
78                  Son_Index := Index_Type'Succ (Son_Index);
79               end if;
80            end if;
81
82            A (To_Index (C)) := A (Son_Index);  -- Move (Son, C);
83         end;
84
85         C := Son;
86      end loop;
87
88      while C /= S loop
89         declare
90            Father : constant T := C / 2;
91         begin
92            if A (To_Index (Father)) < Temp then           -- Lt (Father, 0)
93               A (To_Index (C)) := A (To_Index (Father));  -- Move (Father, C)
94               C := Father;
95            else
96               exit;
97            end if;
98         end;
99      end loop;
100
101      A (To_Index (C)) := Temp; -- Move (0, C);
102   end Sift;
103
104--  Start of processing for Generic_Constrained_Array_Sort
105
106begin
107   for J in reverse 1 .. Max / 2 loop
108      Temp := Container (To_Index (J)); --  Move (J, 0);
109      Sift (J);
110   end loop;
111
112   while Max > 1 loop
113      Temp := A (To_Index (Max));         --  Move (Max, 0);
114      A (To_Index (Max)) := A (A'First);  --  Move (1, Max);
115
116      Max := Max - 1;
117      Sift (1);
118   end loop;
119end Ada.Containers.Generic_Constrained_Array_Sort;
120