gcc/ada/g-bytswa.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUN-TIME COMPONENTS                         --
   4 --                                                                          --
   5 --                    G N A T . B Y T E _ S W A P P I N G                   --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --                     Copyright (C) 2006-2007, AdaCore                     --
  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,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, 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 --  This is a general implementation that does not take advantage of
  35 --  any machine-specific instructions.
  36
  37 with Interfaces; use Interfaces;
  38 with Ada.Unchecked_Conversion;
  39
  40 package body GNAT.Byte_Swapping is
  41
  42    --------------
  43    -- Swapped2 --
  44    --------------
  45
  46    function Swapped2 (Input : Item) return Item is
  47
  48       function As_U16 is new Ada.Unchecked_Conversion
  49          (Source => Item, Target => Unsigned_16);
  50
  51       function As_Item is new Ada.Unchecked_Conversion
  52          (Source => Unsigned_16, Target => Item);
  53
  54       X : constant Unsigned_16 := As_U16 (Input);
  55
  56    begin
  57       return As_Item ((Shift_Left (X, 8)  and 16#FF00#) or
  58                       (Shift_Right (X, 8) and 16#00FF#));
  59    end Swapped2;
  60
  61    --------------
  62    -- Swapped4 --
  63    --------------
  64
  65    function Swapped4 (Input : Item) return Item is
  66
  67       function As_U32 is new Ada.Unchecked_Conversion
  68          (Source => Item, Target => Unsigned_32);
  69
  70       function As_Item is new Ada.Unchecked_Conversion
  71          (Source => Unsigned_32, Target => Item);
  72
  73       X : constant Unsigned_32 := As_U32 (Input);
  74
  75    begin
  76       return As_Item ((Shift_Right (X, 24) and 16#0000_00FF#) or
  77                       (Shift_Right (X, 8)  and 16#0000_FF00#) or
  78                       (Shift_Left (X, 8)   and 16#00FF_0000#) or
  79                       (Shift_Left (X, 24)  and 16#FF00_0000#));
  80    end Swapped4;
  81
  82    --------------
  83    -- Swapped8 --
  84    --------------
  85
  86    function Swapped8 (Input : Item) return Item is
  87
  88       function As_U64 is new Ada.Unchecked_Conversion
  89          (Source => Item, Target => Unsigned_64);
  90
  91       function As_Item is new Ada.Unchecked_Conversion
  92          (Source => Unsigned_64, Target => Item);
  93
  94       X : constant Unsigned_64 := As_U64 (Input);
  95
  96       Low, High : aliased Unsigned_32;
  97
  98    begin
  99       Low := Unsigned_32 (X and 16#0000_0000_FFFF_FFFF#);
 100       Swap4 (Low'Address);
 101       High := Unsigned_32 (Shift_Right (X, 32));
 102       Swap4 (High'Address);
 103       return As_Item
 104          (Shift_Left (Unsigned_64 (Low), 32) or Unsigned_64 (High));
 105    end Swapped8;
 106
 107    -----------
 108    -- Swap2 --
 109    -----------
 110
 111    procedure Swap2 (Location : System.Address) is
 112       X : Unsigned_16;
 113       for X'Address use Location;
 114    begin
 115       X := (Shift_Left (X, 8)  and 16#FF00#) or
 116            (Shift_Right (X, 8) and 16#00FF#);
 117    end Swap2;
 118
 119    -----------
 120    -- Swap4 --
 121    -----------
 122
 123    procedure Swap4 (Location : System.Address) is
 124       X : Unsigned_32;
 125       for X'Address use Location;
 126    begin
 127       X := (Shift_Right (X, 24) and 16#0000_00FF#) or
 128            (Shift_Right (X, 8)  and 16#0000_FF00#) or
 129            (Shift_Left (X, 8)   and 16#00FF_0000#) or
 130            (Shift_Left (X, 24)  and 16#FF00_0000#);
 131    end Swap4;
 132
 133    -----------
 134    -- Swap8 --
 135    -----------
 136
 137    procedure Swap8 (Location : System.Address) is
 138       X : Unsigned_64;
 139       for X'Address use Location;
 140
 141       Low, High : aliased Unsigned_32;
 142
 143    begin
 144       Low := Unsigned_32 (X and 16#0000_0000_FFFF_FFFF#);
 145       Swap4 (Low'Address);
 146       High := Unsigned_32 (Shift_Right (X, 32));
 147       Swap4 (High'Address);
 148       X := Shift_Left (Unsigned_64 (Low), 32) or Unsigned_64 (High);
 149    end Swap8;
 150
 151 end GNAT.Byte_Swapping;