gcc/ada/a-cgaaso.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT LIBRARY COMPONENTS                          --
   4 --                                                                          --
   5 --              ADA.CONTAINERS.GENERIC_ANONYMOUS_ARRAY_SORT                 --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 2004-2009, 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 with System;
  33
  34 procedure Ada.Containers.Generic_Anonymous_Array_Sort
  35   (First, Last : Index_Type'Base)
  36 is
  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    function Lt (J, K : T) return Boolean;
  43    pragma Inline (Lt);
  44
  45    procedure Xchg (J, K : T);
  46    pragma Inline (Xchg);
  47
  48    procedure Sift (S : T);
  49
  50    --------------
  51    -- To_Index --
  52    --------------
  53
  54    function To_Index (J : T) return Index_Type is
  55       K : constant T'Base := Index_Type'Pos (First) + J - T'(1);
  56    begin
  57       return Index_Type'Val (K);
  58    end To_Index;
  59
  60    --------
  61    -- Lt --
  62    --------
  63
  64    function Lt (J, K : T) return Boolean is
  65    begin
  66       return Less (To_Index (J), To_Index (K));
  67    end Lt;
  68
  69    ----------
  70    -- Xchg --
  71    ----------
  72
  73    procedure Xchg (J, K : T) is
  74    begin
  75       Swap (To_Index (J), To_Index (K));
  76    end Xchg;
  77
  78    Max : T := Index_Type'Pos (Last) - Index_Type'Pos (First) + T'(1);
  79
  80    ----------
  81    -- Sift --
  82    ----------
  83
  84    procedure Sift (S : T) is
  85       C      : T := S;
  86       Son    : T;
  87       Father : T;
  88
  89    begin
  90       loop
  91          Son := C + C;
  92
  93          if Son < Max then
  94             if Lt (Son, Son + 1) then
  95                Son := Son + 1;
  96             end if;
  97          elsif Son > Max then
  98             exit;
  99          end if;
 100
 101          Xchg (Son, C);
 102          C := Son;
 103       end loop;
 104
 105       while C /= S loop
 106          Father := C / 2;
 107
 108          if Lt (Father, C) then
 109             Xchg (Father, C);
 110             C := Father;
 111          else
 112             exit;
 113          end if;
 114       end loop;
 115    end Sift;
 116
 117 --  Start of processing for Generic_Anonymous_Array_Sort
 118
 119 begin
 120    for J in reverse 1 .. Max / 2 loop
 121       Sift (J);
 122    end loop;
 123
 124    while Max > 1 loop
 125       Xchg (1, Max);
 126       Max := Max - 1;
 127       Sift (1);
 128    end loop;
 129 end Ada.Containers.Generic_Anonymous_Array_Sort;