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

--                                                                          --

--                 GNAT RUN-TIME LIBRARY (GNARL) COMPONENTS                 --

--                                                                          --

--     S Y S T E M . V E C T O R S . B O O L E A N _ O P E R A T I O N S    --

--                                                                          --

--                                 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.      --

--                                                                          --

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

package body System.Vectors.Boolean_Operations is

   SU : constant := Storage_Unit;

   --  Convenient short hand, used throughout

   --  The coding of this unit depends on the fact that the Component_Size

   --  of a normally declared array of Boolean is equal to Storage_Unit. We

   --  can't use the Component_Size directly since it is non-static. The

   --  following declaration checks that this declaration is correct

   type Boolean_Array is array (Integer range <>) of Boolean;

   pragma Compile_Time_Error

     (Boolean_Array'Component_Size /= SU, "run time compile failure");

   --  NOTE: The boolean literals must be qualified here to avoid visibility

   --  anomalies when this package is compiled through Rtsfind, in a context

   --  that includes a user-defined type derived from boolean.

   True_Val : constant Vector := Standard.True'Enum_Rep

                                   + Standard.True'Enum_Rep * 2**SU

                                   + Standard.True'Enum_Rep * 2**(SU * 2)

                                   + Standard.True'Enum_Rep * 2**(SU * 3)

                                   + Standard.True'Enum_Rep * 2**(SU * 4)

                                   + Standard.True'Enum_Rep * 2**(SU * 5)

                                   + Standard.True'Enum_Rep * 2**(SU * 6)

                                   + Standard.True'Enum_Rep * 2**(SU * 7);

   --  This constant represents the bits to be flipped to perform a logical

   --  "not" on a vector of booleans, independent of the actual

   --  representation of True.

   --  The representations of (False, True) are assumed to be zero/one and

   --  the maximum number of unpacked booleans per Vector is assumed to be 8.

   pragma Assert (Standard.False'Enum_Rep = 0);

   pragma Assert (Standard.True'Enum_Rep = 1);

   pragma Assert (Vector'Size / Storage_Unit <= 8);

   --  The reason we need to do these gymnastics is that no call to

   --  Unchecked_Conversion can be made at the library level since this

   --  unit is pure. Also a conversion from the array type to the Vector type

   --  inside the body of "not" is inefficient because of alignment issues.

   -----------

   -- "not" --

   -----------

   function "not" (Item : Vectors.Vector) return Vectors.Vector is

   begin

      return Item xor True_Val;

   end "not";

   ----------

   -- Nand --

   ----------

   function Nand (Left, Right : Boolean) return Boolean is

   begin

      return not (Left and Right);

   end Nand;

   function Nand (Left, Right : Vectors.Vector) return Vectors.Vector is

   begin

      return not (Left and Right);

   end Nand;

   ---------

   -- Nor --

   ---------

   function Nor (Left, Right : Boolean) return Boolean is

   begin

      return not (Left or Right);

   end Nor;

   function Nor (Left, Right : Vectors.Vector) return Vectors.Vector is

   begin

      return not (Left or Right);

   end Nor;

   ----------

   -- Nxor --

   ----------

   function Nxor (Left, Right : Boolean) return Boolean is

   begin

      return not (Left xor Right);

   end Nxor;

   function Nxor (Left, Right : Vectors.Vector) return Vectors.Vector is

   begin

      return not (Left xor Right);

   end Nxor;

end System.Vectors.Boolean_Operations;