gcc/ada/s-carun8.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 _ U N S I G N E D _ 8      --
   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_Unsigned_8 is
  37
  38    type Word is mod 2 ** 32;
  39    --  Used to process operands by words
  40
  41    type Big_Words is array (Natural) of Word;
  42    type Big_Words_Ptr is access Big_Words;
  43    --  Array type used to access by words
  44
  45    type Byte is mod 2 ** 8;
  46    --  Used to process operands by bytes
  47
  48    type Big_Bytes is array (Natural) of Byte;
  49    type Big_Bytes_Ptr is access Big_Bytes;
  50    --  Array type used to access by bytes
  51
  52    function To_Big_Words is new
  53      Unchecked_Conversion (System.Address, Big_Words_Ptr);
  54
  55    function To_Big_Bytes is new
  56      Unchecked_Conversion (System.Address, Big_Bytes_Ptr);
  57
  58    ----------------------
  59    -- Compare_Array_U8 --
  60    ----------------------
  61
  62    function Compare_Array_U8
  63      (Left      : System.Address;
  64       Right     : System.Address;
  65       Left_Len  : Natural;
  66       Right_Len : Natural)
  67       return      Integer
  68    is
  69       Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
  70
  71    begin
  72       --  If operands are non-aligned, or length is too short, go by bytes
  73
  74       if (((Left or Right) and 2#11#) /= 0) or else Compare_Len < 4 then
  75          return Compare_Array_U8_Unaligned (Left, Right, Left_Len, Right_Len);
  76       end if;
  77
  78       --  Here we can go by words
  79
  80       declare
  81          LeftP  : constant Big_Words_Ptr := To_Big_Words (Left);
  82          RightP : constant Big_Words_Ptr := To_Big_Words (Right);
  83          Clen4  : constant Natural       := Compare_Len / 4 - 1;
  84          Clen4F : constant Natural       := Clen4 * 4;
  85
  86       begin
  87          for J in 0 .. Clen4 loop
  88             if LeftP (J) /= RightP (J) then
  89                return Compare_Array_U8_Unaligned
  90                         (Left  + Address (4 * J),
  91                          Right + Address (4 * J),
  92                          4, 4);
  93             end if;
  94          end loop;
  95
  96          return Compare_Array_U8_Unaligned
  97                   (Left      + Address (Clen4F),
  98                    Right     + Address (Clen4F),
  99                    Left_Len  - Clen4F,
 100                    Right_Len - Clen4F);
 101       end;
 102    end Compare_Array_U8;
 103
 104    --------------------------------
 105    -- Compare_Array_U8_Unaligned --
 106    --------------------------------
 107
 108    function Compare_Array_U8_Unaligned
 109      (Left      : System.Address;
 110       Right     : System.Address;
 111       Left_Len  : Natural;
 112       Right_Len : Natural)
 113       return      Integer
 114    is
 115       Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);
 116
 117       LeftP  : constant Big_Bytes_Ptr := To_Big_Bytes (Left);
 118       RightP : constant Big_Bytes_Ptr := To_Big_Bytes (Right);
 119
 120    begin
 121       for J in 0 .. Compare_Len - 1 loop
 122          if LeftP (J) /= RightP (J) then
 123             if LeftP (J) > RightP (J) then
 124                return +1;
 125             else
 126                return -1;
 127             end if;
 128          end if;
 129       end loop;
 130
 131       if Left_Len = Right_Len then
 132          return 0;
 133       elsif Left_Len > Right_Len then
 134          return +1;
 135       else
 136          return -1;
 137       end if;
 138    end Compare_Array_U8_Unaligned;
 139
 140 end System.Compare_Array_Unsigned_8;