gcc/ada/libgnat/a-cogeso.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT LIBRARY COMPONENTS                          --
   4 --                                                                          --
   5 --                       ADA.CONTAINERS.GENERIC_SORT                        --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --            Copyright (C) 2011-2024, 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
  32 procedure 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
 115 begin
 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;
 125 end Ada.Containers.Generic_Sort;