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

--                                                                          --

--                         GNAT RUN-TIME COMPONENTS                         --

--                                                                          --

--                       S Y S T E M . P A C K _ 2 0                        --

--                                                                          --

--                                 B o d y                                  --

--                                                                          --

--          Copyright (C) 1992-2009, 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.      --

--                                                                          --

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

with System.Storage_Elements;

with System.Unsigned_Types;

with Ada.Unchecked_Conversion;

package body System.Pack_20 is

   subtype Ofs is System.Storage_Elements.Storage_Offset;

   subtype Uns is System.Unsigned_Types.Unsigned;

   subtype N07 is System.Unsigned_Types.Unsigned range 0 .. 7;

   use type System.Storage_Elements.Storage_Offset;

   use type System.Unsigned_Types.Unsigned;

   type Cluster is record

      E0, E1, E2, E3, E4, E5, E6, E7 : Bits_20;

   end record;

   for Cluster use record

      E0 at 0 range 0 * Bits .. 0 * Bits + Bits - 1;

      E1 at 0 range 1 * Bits .. 1 * Bits + Bits - 1;

      E2 at 0 range 2 * Bits .. 2 * Bits + Bits - 1;

      E3 at 0 range 3 * Bits .. 3 * Bits + Bits - 1;

      E4 at 0 range 4 * Bits .. 4 * Bits + Bits - 1;

      E5 at 0 range 5 * Bits .. 5 * Bits + Bits - 1;

      E6 at 0 range 6 * Bits .. 6 * Bits + Bits - 1;

      E7 at 0 range 7 * Bits .. 7 * Bits + Bits - 1;

   end record;

   for Cluster'Size use Bits * 8;

   for Cluster'Alignment use Integer'Min (Standard'Maximum_Alignment,

     1 +

     1 * Boolean'Pos (Bits mod 2 = 0) +

     2 * Boolean'Pos (Bits mod 4 = 0));

   --  Use maximum possible alignment, given the bit field size, since this

   --  will result in the most efficient code possible for the field.

   type Cluster_Ref is access Cluster;

   function To_Ref is new

     Ada.Unchecked_Conversion (System.Address, Cluster_Ref);

   --  The following declarations are for the case where the address

   --  passed to GetU_20 or SetU_20 is not guaranteed to be aligned.

   --  These routines are used when the packed array is itself a

   --  component of a packed record, and therefore may not be aligned.

   type ClusterU is new Cluster;

   for ClusterU'Alignment use 1;

   type ClusterU_Ref is access ClusterU;

   function To_Ref is new

     Ada.Unchecked_Conversion (System.Address, ClusterU_Ref);

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

   -- Get_20 --

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

   function Get_20 (Arr : System.Address; N : Natural) return Bits_20 is

      C : constant Cluster_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));

   begin

      case N07 (Uns (N) mod 8) is

         when 0 => return C.E0;

         when 1 => return C.E1;

         when 2 => return C.E2;

         when 3 => return C.E3;

         when 4 => return C.E4;

         when 5 => return C.E5;

         when 6 => return C.E6;

         when 7 => return C.E7;

      end case;

   end Get_20;

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

   -- GetU_20 --

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

   function GetU_20 (Arr : System.Address; N : Natural) return Bits_20 is

      C : constant ClusterU_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));

   begin

      case N07 (Uns (N) mod 8) is

         when 0 => return C.E0;

         when 1 => return C.E1;

         when 2 => return C.E2;

         when 3 => return C.E3;

         when 4 => return C.E4;

         when 5 => return C.E5;

         when 6 => return C.E6;

         when 7 => return C.E7;

      end case;

   end GetU_20;

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

   -- Set_20 --

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

   procedure Set_20 (Arr : System.Address; N : Natural; E : Bits_20) is

      C : constant Cluster_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));

   begin

      case N07 (Uns (N) mod 8) is

         when 0 => C.E0 := E;

         when 1 => C.E1 := E;

         when 2 => C.E2 := E;

         when 3 => C.E3 := E;

         when 4 => C.E4 := E;

         when 5 => C.E5 := E;

         when 6 => C.E6 := E;

         when 7 => C.E7 := E;

      end case;

   end Set_20;

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

   -- SetU_20 --

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

   procedure SetU_20 (Arr : System.Address; N : Natural; E : Bits_20) is

      C : constant ClusterU_Ref := To_Ref (Arr + Bits * Ofs (Uns (N) / 8));

   begin

      case N07 (Uns (N) mod 8) is

         when 0 => C.E0 := E;

         when 1 => C.E1 := E;

         when 2 => C.E2 := E;

         when 3 => C.E3 := E;

         when 4 => C.E4 := E;

         when 5 => C.E5 := E;

         when 6 => C.E6 := E;

         when 7 => C.E7 := E;

      end case;

   end SetU_20;

end System.Pack_20;