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------------------------------------------------------------------------------

--                                                                          --

--                    GNAT RUN-TIME LIBRARY COMPONENTS                      --

--                                                                          --

--       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      --

--                                                                          --

--                                 B o d y                                  --

--                                                                          --

--          Copyright (C) 2002-2009, Free Software Foundation, Inc.         --

--                                                                          --

-- GNAT is free software;  you can  redistribute it  and/or modify it under --

-- terms of the  GNU General Public License as published  by the Free Soft- --

-- ware  Foundation;  either version 3,  or (at your option) any later ver- --

-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --

-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --

-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --

--                                                                          --

-- As a special exception under Section 7 of GPL version 3, you are granted --

-- additional permissions described in the GCC Runtime Library Exception,   --

-- version 3.1, as published by the Free Software Foundation.               --

--                                                                          --

-- You should have received a copy of the GNU General Public License and    --

-- a copy of the GCC Runtime Library Exception along with this program;     --

-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --

-- <http://www.gnu.org/licenses/>.                                          --

--                                                                          --

-- GNAT was originally developed  by the GNAT team at  New York University. --

-- Extensive contributions were provided by Ada Core Technologies Inc.      --

--                                                                          --

------------------------------------------------------------------------------

pragma Compiler_Unit;

with System.Address_Operations; use System.Address_Operations;

with Ada.Unchecked_Conversion;

package body System.Compare_Array_Unsigned_8 is

   type Word is mod 2 ** 32;

   --  Used to process operands by words

   type Big_Words is array (Natural) of Word;

   type Big_Words_Ptr is access Big_Words;

   for Big_Words_Ptr'Storage_Size use 0;

   --  Array type used to access by words

   type Byte is mod 2 ** 8;

   --  Used to process operands by bytes

   type Big_Bytes is array (Natural) of Byte;

   type Big_Bytes_Ptr is access Big_Bytes;

   for Big_Bytes_Ptr'Storage_Size use 0;

   --  Array type used to access by bytes

   function To_Big_Words is new

     Ada.Unchecked_Conversion (System.Address, Big_Words_Ptr);

   function To_Big_Bytes is new

     Ada.Unchecked_Conversion (System.Address, Big_Bytes_Ptr);

   ----------------------

   -- Compare_Array_U8 --

   ----------------------

   function Compare_Array_U8

     (Left      : System.Address;

      Right     : System.Address;

      Left_Len  : Natural;

      Right_Len : Natural) return Integer

   is

      Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);

   begin

      --  If operands are non-aligned, or length is too short, go by bytes

      if (ModA (OrA (Left, Right), 4) /= 0) or else Compare_Len < 4 then

         return Compare_Array_U8_Unaligned (Left, Right, Left_Len, Right_Len);

      end if;

      --  Here we can go by words

      declare

         LeftP                   : constant Big_Words_Ptr :=

                                     To_Big_Words (Left);

         RightP                  : constant Big_Words_Ptr :=

                                     To_Big_Words (Right);

         Words_To_Compare        : constant Natural := Compare_Len / 4;

         Bytes_Compared_As_Words : constant Natural := Words_To_Compare * 4;

      begin

         for J in 0 .. Words_To_Compare - 1 loop

            if LeftP (J) /= RightP (J) then

               return Compare_Array_U8_Unaligned

                        (AddA (Left,  Address (4 * J)),

                         AddA (Right, Address (4 * J)),

                         4, 4);

            end if;

         end loop;

         return Compare_Array_U8_Unaligned

                  (AddA (Left,  Address (Bytes_Compared_As_Words)),

                   AddA (Right, Address (Bytes_Compared_As_Words)),

                   Left_Len  - Bytes_Compared_As_Words,

                   Right_Len - Bytes_Compared_As_Words);

      end;

   end Compare_Array_U8;

   --------------------------------

   -- Compare_Array_U8_Unaligned --

   --------------------------------

   function Compare_Array_U8_Unaligned

     (Left      : System.Address;

      Right     : System.Address;

      Left_Len  : Natural;

      Right_Len : Natural) return Integer

   is

      Compare_Len : constant Natural := Natural'Min (Left_Len, Right_Len);

      LeftP  : constant Big_Bytes_Ptr := To_Big_Bytes (Left);

      RightP : constant Big_Bytes_Ptr := To_Big_Bytes (Right);

   begin

      for J in 0 .. Compare_Len - 1 loop

         if LeftP (J) /= RightP (J) then

            if LeftP (J) > RightP (J) then

               return +1;

            else

               return -1;

            end if;

         end if;

      end loop;

      if Left_Len = Right_Len then

         return 0;

      elsif Left_Len > Right_Len then

         return +1;

      else

         return -1;

      end if;

   end Compare_Array_U8_Unaligned;

end System.Compare_Array_Unsigned_8;