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------------------------------------------------------------------------------
-- --
-- GNAT RUNTIME COMPONENTS --
-- --
-- S Y S T E M . P A C K _ 2 3 --
-- --
-- B o d y --
-- --
-- Copyright (C) 1992-1999 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 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, 59 Temple Place - Suite 330, Boston, --
-- MA 02111-1307, 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. --
-- --
------------------------------------------------------------------------------
with System.Storage_Elements;
with System.Unsigned_Types;
with Unchecked_Conversion;
package body System.Pack_23 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_23;
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
Unchecked_Conversion (System.Address, Cluster_Ref);
------------
-- Get_23 --
------------
function Get_23 (Arr : System.Address; N : Natural) return Bits_23 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_23;
------------
-- Set_23 --
------------
procedure Set_23 (Arr : System.Address; N : Natural; E : Bits_23) 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_23;
end System.Pack_23;
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