1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT LIBRARY COMPONENTS                          --
4--                                                                          --
5--              ADA.CONTAINERS.GENERIC_CONSTRAINED_ARRAY_SORT               --
6--                                                                          --
7--                                 B o d y                                  --
8--                                                                          --
9--          Copyright (C) 2004-2019, 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
32with System;
33
34procedure Ada.Containers.Generic_Constrained_Array_Sort
35  (Container : in out Array_Type)
36is
37   type T is range System.Min_Int .. System.Max_Int;
38
39   function To_Index (J : T) return Index_Type;
40   pragma Inline (To_Index);
41
42   procedure Sift (S : T);
43
44   A : Array_Type renames Container;
45
46   --------------
47   -- To_Index --
48   --------------
49
50   function To_Index (J : T) return Index_Type is
51      K : constant T'Base := Index_Type'Pos (A'First) + J - T'(1);
52   begin
53      return Index_Type'Val (K);
54   end To_Index;
55
56   Max  : T := A'Length;
57   Temp : Element_Type;
58
59   ----------
60   -- Sift --
61   ----------
62
63   procedure Sift (S : T) is
64      C   : T := S;
65      Son : T;
66
67   begin
68      loop
69         Son := 2 * C;
70
71         exit when Son > Max;
72
73         declare
74            Son_Index : Index_Type := To_Index (Son);
75
76         begin
77            if Son < Max then
78               if A (Son_Index) < A (Index_Type'Succ (Son_Index)) then
79                  Son := Son + 1;
80                  Son_Index := Index_Type'Succ (Son_Index);
81               end if;
82            end if;
83
84            A (To_Index (C)) := A (Son_Index);  -- Move (Son, C);
85         end;
86
87         C := Son;
88      end loop;
89
90      while C /= S loop
91         declare
92            Father : constant T := C / 2;
93         begin
94            if A (To_Index (Father)) < Temp then           -- Lt (Father, 0)
95               A (To_Index (C)) := A (To_Index (Father));  -- Move (Father, C)
96               C := Father;
97            else
98               exit;
99            end if;
100         end;
101      end loop;
102
103      A (To_Index (C)) := Temp; -- Move (0, C);
104   end Sift;
105
106--  Start of processing for Generic_Constrained_Array_Sort
107
108begin
109   for J in reverse 1 .. Max / 2 loop
110      Temp := Container (To_Index (J)); --  Move (J, 0);
111      Sift (J);
112   end loop;
113
114   while Max > 1 loop
115      Temp := A (To_Index (Max));         --  Move (Max, 0);
116      A (To_Index (Max)) := A (A'First);  --  Move (1, Max);
117
118      Max := Max - 1;
119      Sift (1);
120   end loop;
121end Ada.Containers.Generic_Constrained_Array_Sort;
122