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

--                                                                          --

--                         GNAT RUN-TIME COMPONENTS                         --

--                                                                          --

--                    G N A T . B Y T E _ S W A P P I N G                   --

--                                                                          --

--                                 B o d y                                  --

--                                                                          --

--                     Copyright (C) 2006-2007, AdaCore                     --

--                                                                          --

-- 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 2,  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.  See the GNU General Public License --

-- for  more details.  You should have  received  a copy of the GNU General --

-- Public License  distributed with GNAT;  see file COPYING.  If not, write --

-- to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, --

-- Boston, MA 02110-1301, USA.                                              --

--                                                                          --

-- As a special exception,  if other files  instantiate  generics from this --

-- unit, or you link  this unit with other files  to produce an executable, --

-- this  unit  does not  by itself cause  the resulting  executable  to  be --

-- covered  by the  GNU  General  Public  License.  This exception does not --

-- however invalidate  any other reasons why  the executable file  might be --

-- covered by the  GNU Public License.                                      --

--                                                                          --

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

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

--                                                                          --

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

--  This is a machine-specific version of this package.

--  It uses instructions available on Intel 486 processors (or later).

with Interfaces;          use Interfaces;

with System.Machine_Code; use System.Machine_Code;

with Ada.Unchecked_Conversion;

package body GNAT.Byte_Swapping is

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

   -- Local Subprograms --

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

   function Swapped32 (Value : Unsigned_32) return Unsigned_32;

   pragma Inline_Always (Swapped32);

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

   -- Swapped2 --

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

   function Swapped2 (Input : Item) return Item is

      function As_U16 is new Ada.Unchecked_Conversion

         (Source => Item, Target => Unsigned_16);

      function As_Item is new Ada.Unchecked_Conversion

         (Source => Unsigned_16, Target => Item);

      X : Unsigned_16 := As_U16 (Input);

   begin

      Asm ("xchgb %b0,%h0",

           Unsigned_16'Asm_Output ("=q", X),

           Unsigned_16'Asm_Input ("0", X));

      return As_Item (X);

   end Swapped2;

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

   -- Swapped4 --

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

   function Swapped4 (Input : Item) return Item is

      function As_U32 is new Ada.Unchecked_Conversion

         (Source => Item, Target => Unsigned_32);

      function As_Item is new Ada.Unchecked_Conversion

         (Source => Unsigned_32, Target => Item);

      X : Unsigned_32 := As_U32 (Input);

   begin

      Asm ("bswap %0",

           Unsigned_32'Asm_Output ("=r", X),

           Unsigned_32'Asm_Input ("0", X));

      return As_Item (X);

   end Swapped4;

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

   -- Swapped8 --

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

   function Swapped8 (Input : Item) return Item is

      function As_U64 is new Ada.Unchecked_Conversion

         (Source => Item, Target => Unsigned_64);

      X : constant Unsigned_64 := As_U64 (Input);

      type Two_Words is array (0 .. 1) of Unsigned_32;

      for Two_Words'Component_Size use Unsigned_32'Size;

      function As_Item is new Ada.Unchecked_Conversion

        (Source => Two_Words, Target => Item);

      Result : Two_Words;

   begin

      Asm ("xchgl %0,%1",

         Outputs =>

            (Unsigned_32'Asm_Output ("=r", Result (0)),

             Unsigned_32'Asm_Output ("=r", Result (1))),

         Inputs =>

            (Unsigned_32'Asm_Input ("0",

                Swapped32 (Unsigned_32 (X and 16#0000_0000_FFFF_FFFF#))),

             Unsigned_32'Asm_Input ("1",

                Swapped32 (Unsigned_32 (Shift_Right (X, 32))))));

      return As_Item (Result);

   end Swapped8;

   -----------

   -- Swap2 --

   -----------

   procedure Swap2 (Location : System.Address) is

      X : Unsigned_16;

      for X'Address use Location;

   begin

      Asm ("xchgb %b0,%h0",

           Unsigned_16'Asm_Output ("=q", X),

           Unsigned_16'Asm_Input ("0", X));

   end Swap2;

   -----------

   -- Swap4 --

   -----------

   procedure Swap4 (Location : System.Address) is

      X : Unsigned_32;

      for X'Address use Location;

   begin

      Asm ("bswap %0",

           Unsigned_32'Asm_Output ("=r", X),

           Unsigned_32'Asm_Input ("0", X));

   end Swap4;

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

   -- Swapped32 --

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

   function Swapped32 (Value : Unsigned_32) return Unsigned_32 is

      X : Unsigned_32 := Value;

   begin

      Asm ("bswap %0",

           Unsigned_32'Asm_Output ("=r", X),

           Unsigned_32'Asm_Input ("0", X));

      return X;

   end Swapped32;

   -----------

   -- Swap8 --

   -----------

   procedure Swap8 (Location : System.Address) is

      X : Unsigned_64;

      for X'Address use Location;

      type Two_Words is array (0 .. 1) of Unsigned_32;

      for Two_Words'Component_Size use Unsigned_32'Size;

      Words : Two_Words;

      for Words'Address use Location;

   begin

      Asm ("xchgl %0,%1",

         Outputs =>

            (Unsigned_32'Asm_Output ("=r", Words (0)),

             Unsigned_32'Asm_Output ("=r", Words (1))),

         Inputs =>

            (Unsigned_32'Asm_Input ("0",

                Swapped32 (Unsigned_32 (X and 16#0000_0000_FFFF_FFFF#))),

             Unsigned_32'Asm_Input ("1",

                Swapped32 (Unsigned_32 (Shift_Right (X, 32))))));

   end Swap8;

end GNAT.Byte_Swapping;