1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT LIBRARY COMPONENTS                          --
4--                                                                          --
5--                       ADA.CONTAINERS.GENERIC_SORT                        --
6--                                                                          --
7--                                 B o d y                                  --
8--                                                                          --
9--            Copyright (C) 2011-2021, 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 (see g-heasor.ad[sb])
31
32procedure Ada.Containers.Generic_Sort (First, Last : Index_Type'Base) is
33   subtype T is Long_Long_Integer;
34
35   function To_Index (J : T) return Index_Type;
36   pragma Inline (To_Index);
37
38   function Lt (J, K : T) return Boolean;
39   pragma Inline (Lt);
40
41   procedure Xchg (J, K : T);
42   pragma Inline (Xchg);
43
44   procedure Sift (S : T);
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 (First) + J - T'(1);
52   begin
53      return Index_Type'Val (K);
54   end To_Index;
55
56   --------
57   -- Lt --
58   --------
59
60   function Lt (J, K : T) return Boolean is
61   begin
62      return Before (To_Index (J), To_Index (K));
63   end Lt;
64
65   ----------
66   -- Xchg --
67   ----------
68
69   procedure Xchg (J, K : T) is
70   begin
71      Swap (To_Index (J), To_Index (K));
72   end Xchg;
73
74   Max : T := Index_Type'Pos (Last) - Index_Type'Pos (First) + T'(1);
75
76   ----------
77   -- Sift --
78   ----------
79
80   procedure Sift (S : T) is
81      C      : T := S;
82      Son    : T;
83      Father : T;
84
85   begin
86      loop
87         Son := C + C;
88
89         if Son < Max then
90            if Lt (Son, Son + 1) then
91               Son := Son + 1;
92            end if;
93         elsif Son > Max then
94            exit;
95         end if;
96
97         Xchg (Son, C);
98         C := Son;
99      end loop;
100
101      while C /= S loop
102         Father := C / 2;
103
104         if Lt (Father, C) then
105            Xchg (Father, C);
106            C := Father;
107         else
108            exit;
109         end if;
110      end loop;
111   end Sift;
112
113--  Start of processing for Generic_Sort
114
115begin
116   for J in reverse 1 .. Max / 2 loop
117      Sift (J);
118   end loop;
119
120   while Max > 1 loop
121      Xchg (1, Max);
122      Max := Max - 1;
123      Sift (1);
124   end loop;
125end Ada.Containers.Generic_Sort;
126