gcc/ada/a-cgaaso.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT LIBRARY COMPONENTS                          --
   4 --                                                                          --
   5 --                      A D A . C O N T A I N E R S .                       --
   6 --        G E N E R I C _ A N O N Y M O U S _ A R R A Y _ S O R T           --
   7 --                                                                          --
   8 --                                 B o d y                                  --
   9 --                                                                          --
  10 --          Copyright (C) 2004-2006, Free Software Foundation, Inc.         --
  11 --                                                                          --
  12 -- This specification is derived from the Ada Reference Manual for use with --
  13 -- GNAT. The copyright notice above, and the license provisions that follow --
  14 -- apply solely to the  contents of the part following the private keyword. --
  15 --                                                                          --
  16 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  17 -- terms of the  GNU General Public License as published  by the Free Soft- --
  18 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  19 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  20 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  21 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  22 -- for  more details.  You should have  received  a copy of the GNU General --
  23 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  24 -- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --
  25 -- Boston, MA 02110-1301, USA.                                              --
  26 --                                                                          --
  27 -- As a special exception,  if other files  instantiate  generics from this --
  28 -- unit, or you link  this unit with other files  to produce an executable, --
  29 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  30 -- covered  by the  GNU  General  Public  License.  This exception does not --
  31 -- however invalidate  any other reasons why  the executable file  might be --
  32 -- covered by the  GNU Public License.                                      --
  33 --                                                                          --
  34 -- This unit was originally developed by Matthew J Heaney.                  --
  35 ------------------------------------------------------------------------------
  36
  37 --  This algorithm was adapted from GNAT.Heap_Sort (see g-heasor.ad[sb]).
  38
  39 with System;
  40
  41 procedure Ada.Containers.Generic_Anonymous_Array_Sort
  42   (First, Last : Index_Type'Base)
  43 is
  44    type T is range System.Min_Int .. System.Max_Int;
  45
  46    function To_Index (J : T) return Index_Type;
  47    pragma Inline (To_Index);
  48
  49    function Lt (J, K : T) return Boolean;
  50    pragma Inline (Lt);
  51
  52    procedure Xchg (J, K : T);
  53    pragma Inline (Xchg);
  54
  55    procedure Sift (S : T);
  56
  57    --------------
  58    -- To_Index --
  59    --------------
  60
  61    function To_Index (J : T) return Index_Type is
  62       K : constant T'Base := Index_Type'Pos (First) + J - T'(1);
  63    begin
  64       return Index_Type'Val (K);
  65    end To_Index;
  66
  67    --------
  68    -- Lt --
  69    --------
  70
  71    function Lt (J, K : T) return Boolean is
  72    begin
  73       return Less (To_Index (J), To_Index (K));
  74    end Lt;
  75
  76    ----------
  77    -- Xchg --
  78    ----------
  79
  80    procedure Xchg (J, K : T) is
  81    begin
  82       Swap (To_Index (J), To_Index (K));
  83    end Xchg;
  84
  85    Max : T := Index_Type'Pos (Last) - Index_Type'Pos (First) + T'(1);
  86
  87    ----------
  88    -- Sift --
  89    ----------
  90
  91    procedure Sift (S : T) is
  92       C      : T := S;
  93       Son    : T;
  94       Father : T;
  95
  96    begin
  97       loop
  98          Son := C + C;
  99
 100          if Son < Max then
 101             if Lt (Son, Son + 1) then
 102                Son := Son + 1;
 103             end if;
 104          elsif Son > Max then
 105             exit;
 106          end if;
 107
 108          Xchg (Son, C);
 109          C := Son;
 110       end loop;
 111
 112       while C /= S loop
 113          Father := C / 2;
 114
 115          if Lt (Father, C) then
 116             Xchg (Father, C);
 117             C := Father;
 118          else
 119             exit;
 120          end if;
 121       end loop;
 122    end Sift;
 123
 124 --  Start of processing for Generic_Anonymous_Array_Sort
 125
 126 begin
 127    for J in reverse 1 .. Max / 2 loop
 128       Sift (J);
 129    end loop;
 130
 131    while Max > 1 loop
 132       Xchg (1, Max);
 133       Max := Max - 1;
 134       Sift (1);
 135    end loop;
 136 end Ada.Containers.Generic_Anonymous_Array_Sort;