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1 706 jeremybenn
------------------------------------------------------------------------------
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--                                                                          --
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--                         GNAT RUN-TIME COMPONENTS                         --
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--                                                                          --
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--                    G N A T . B Y T E _ S W A P P I N G                   --
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--                                                                          --
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--                                 B o d y                                  --
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--                                                                          --
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--                     Copyright (C) 2006-2012, AdaCore                     --
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--                                                                          --
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-- GNAT is free software;  you can  redistribute it  and/or modify it under --
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-- terms of the  GNU General Public License as published  by the Free Soft- --
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-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
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-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
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--                                                                          --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception,   --
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-- version 3.1, as published by the Free Software Foundation.               --
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--                                                                          --
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-- You should have received a copy of the GNU General Public License and    --
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-- a copy of the GCC Runtime Library Exception along with this program;     --
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-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
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-- <http://www.gnu.org/licenses/>.                                          --
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--                                                                          --
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-- GNAT was originally developed  by the GNAT team at  New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc.      --
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--                                                                          --
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------------------------------------------------------------------------------
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--  This is a general implementation that uses GCC intrinsics to take
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--  advantage of any machine-specific instructions.
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with Ada.Unchecked_Conversion; use Ada;
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package body GNAT.Byte_Swapping is
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   type U16 is mod 2**16;
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   type U32 is mod 2**32;
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   type U64 is mod 2**64;
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   function Bswap_16 (X : U16) return U16 is (X / 256 or X * 256);
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   --  The above is an idiom recognized by GCC
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   function Bswap_32 (X : U32) return U32;
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   pragma Import (Intrinsic, Bswap_32, "__builtin_bswap32");
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   function Bswap_64 (X : U64) return U64;
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   pragma Import (Intrinsic, Bswap_64, "__builtin_bswap64");
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   --------------
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   -- Swapped2 --
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   --------------
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   function Swapped2 (Input : Item) return Item is
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      function As_U16 is new Unchecked_Conversion (Item, U16);
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      function As_Item is new Unchecked_Conversion (U16, Item);
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      function Bswap_16 (X : U16) return U16 is (X / 256 or X * 256);
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      --  ??? Need to have function local here to allow inlining
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      pragma Compile_Time_Error (Item'Max_Size_In_Storage_Elements /= 2,
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        "storage size must be 2 bytes");
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   begin
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      return As_Item (Bswap_16 (As_U16 (Input)));
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   end Swapped2;
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   --------------
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   -- Swapped4 --
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   --------------
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   function Swapped4 (Input : Item) return Item is
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      function As_U32 is new Unchecked_Conversion (Item, U32);
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      function As_Item is new Unchecked_Conversion (U32, Item);
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      pragma Compile_Time_Error (Item'Max_Size_In_Storage_Elements /= 4,
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        "storage size must be 4 bytes");
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   begin
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      return As_Item (Bswap_32 (As_U32 (Input)));
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   end Swapped4;
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   --------------
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   -- Swapped8 --
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   --------------
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   function Swapped8 (Input : Item) return Item is
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      function As_U64 is new Unchecked_Conversion (Item, U64);
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      function As_Item is new Unchecked_Conversion (U64, Item);
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      pragma Compile_Time_Error (Item'Max_Size_In_Storage_Elements /= 8,
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        "storage size must be 8 bytes");
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   begin
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      return As_Item (Bswap_64 (As_U64 (Input)));
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   end Swapped8;
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   -----------
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   -- Swap2 --
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   -----------
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   procedure Swap2 (Location : System.Address) is
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      X : U16;
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      for X'Address use Location;
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   begin
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      X := Bswap_16 (X);
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   end Swap2;
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   -----------
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   -- Swap4 --
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   -----------
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   procedure Swap4 (Location : System.Address) is
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      X : U32;
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      for X'Address use Location;
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   begin
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      X := Bswap_32 (X);
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   end Swap4;
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   -----------
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   -- Swap8 --
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   -----------
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   procedure Swap8 (Location : System.Address) is
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      X : U64;
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      for X'Address use Location;
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   begin
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      X := Bswap_64 (X);
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   end Swap8;
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end GNAT.Byte_Swapping;

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