gcc/ada/s-casi32.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                   GNU ADA RUNTIME LIBRARY COMPONENTS                     --
   4 --                                                                          --
   5 --        S Y S T E M . C O M P A R E _ A R R A Y _ S I G N E D _ 3 2       --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --             Copyright (C) 2002 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 2,  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.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  20 -- MA 02111-1307, USA.                                                      --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNAT was originally developed  by the GNAT team at  New York University. --
  30 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 with Unchecked_Conversion;
  35
  36 package body System.Compare_Array_Signed_32 is
  37
  38    type Word is range -2**31 .. 2**31 - 1;
  39    for Word'Size use 32;
  40    --  Used to process operands by words
  41
  42    type Uword is record
  43       W : Word;
  44    end record;
  45    pragma Pack (Uword);
  46    for Uword'Alignment use 1;
  47    --  Used to process operands when unaligned
  48
  49    type WP is access Word;
  50    type UP is access Uword;
  51
  52    function W is new Unchecked_Conversion (Address, WP);
  53    function U is new Unchecked_Conversion (Address, UP);
  54
  55    -----------------------
  56    -- Compare_Array_S32 --
  57    -----------------------
  58
  59    function Compare_Array_S32
  60      (Left      : System.Address;
  61       Right     : System.Address;
  62       Left_Len  : Natural;
  63       Right_Len : Natural)
  64       return      Integer
  65    is
  66       Clen : Natural := Natural'Min (Left_Len, Right_Len);
  67       --  Number of elements left to compare
  68
  69       L : Address := Left;
  70       R : Address := Right;
  71       --  Pointers to next elements to compare
  72
  73    begin
  74       --  Case of going by aligned words
  75
  76       if ((Left or Right) and (4 - 1)) = 0 then
  77          while Clen /= 0 loop
  78             if W (L).all /= W (R).all then
  79                if W (L).all > W (R).all then
  80                   return +1;
  81                else
  82                   return -1;
  83                end if;
  84             end if;
  85
  86             Clen := Clen - 1;
  87             L := L + 4;
  88             R := R + 4;
  89          end loop;
  90
  91       --  Case of going by unaligned words
  92
  93       else
  94          while Clen /= 0 loop
  95             if U (L).W /= U (R).W then
  96                if U (L).W > U (R).W then
  97                   return +1;
  98                else
  99                   return -1;
 100                end if;
 101             end if;
 102
 103             Clen := Clen - 1;
 104             L := L + 4;
 105             R := R + 4;
 106          end loop;
 107       end if;
 108
 109       --  Here if common section equal, result decided by lengths
 110
 111       if Left_Len = Right_Len then
 112          return 0;
 113       elsif Left_Len > Right_Len then
 114          return +1;
 115       else
 116          return -1;
 117       end if;
 118    end Compare_Array_S32;
 119
 120 end System.Compare_Array_Signed_32;