gcc/ada/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, 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_Sort (First, Last : Index_Type'Base) is
  35    type T is range System.Min_Int .. System.Max_Int;
  36
  37    function To_Index (J : T) return Index_Type;
  38    pragma Inline (To_Index);
  39
  40    function Lt (J, K : T) return Boolean;
  41    pragma Inline (Lt);
  42
  43    procedure Xchg (J, K : T);
  44    pragma Inline (Xchg);
  45
  46    procedure Sift (S : T);
  47
  48    --------------
  49    -- To_Index --
  50    --------------
  51
  52    function To_Index (J : T) return Index_Type is
  53       K : constant T'Base := Index_Type'Pos (First) + J - T'(1);
  54    begin
  55       return Index_Type'Val (K);
  56    end To_Index;
  57
  58    --------
  59    -- Lt --
  60    --------
  61
  62    function Lt (J, K : T) return Boolean is
  63    begin
  64       return Before (To_Index (J), To_Index (K));
  65    end Lt;
  66
  67    ----------
  68    -- Xchg --
  69    ----------
  70
  71    procedure Xchg (J, K : T) is
  72    begin
  73       Swap (To_Index (J), To_Index (K));
  74    end Xchg;
  75
  76    Max : T := Index_Type'Pos (Last) - Index_Type'Pos (First) + T'(1);
  77
  78    ----------
  79    -- Sift --
  80    ----------
  81
  82    procedure Sift (S : T) is
  83       C      : T := S;
  84       Son    : T;
  85       Father : T;
  86
  87    begin
  88       loop
  89          Son := C + C;
  90
  91          if Son < Max then
  92             if Lt (Son, Son + 1) then
  93                Son := Son + 1;
  94             end if;
  95          elsif Son > Max then
  96             exit;
  97          end if;
  98
  99          Xchg (Son, C);
 100          C := Son;
 101       end loop;
 102
 103       while C /= S loop
 104          Father := C / 2;
 105
 106          if Lt (Father, C) then
 107             Xchg (Father, C);
 108             C := Father;
 109          else
 110             exit;
 111          end if;
 112       end loop;
 113    end Sift;
 114
 115 --  Start of processing for Generic_Sort
 116
 117 begin
 118    for J in reverse 1 .. Max / 2 loop
 119       Sift (J);
 120    end loop;
 121
 122    while Max > 1 loop
 123       Xchg (1, Max);
 124       Max := Max - 1;
 125       Sift (1);
 126    end loop;
 127 end Ada.Containers.Generic_Sort;